SL响应P条件激活不同激素途径以调控根系生长-2012

REVIEW:PART OF A SPECIAL ISSUE ON MATCHING

ROOTS TO THEIR ENVIRONMENT

Strigolactones activate different hormonal pathways for regulation of root

development in response to phosphate growth conditions

Hinanit Koltai

Institute of Plant Sciences,Agricultural Research Organization (ARO),the Volcani Center,PO Box 6,Bet Dagan 50250,Israel

*For correspondence.E-mail hkoltai@https://www.wendangku.net/doc/fd17556379.html,.il

Received:6June 2012Returned for revision:7August 2012Accepted:20August 2012

?Background Strigolactones (SLs)–a group of plant hormones and their derivatives –have been found to play a role in the regulation of root development,in addition to their role in suppression of lateral shoot branching:they alter root architecture and affect root-hair elongation,and SL signalling is necessary for the root response to low phosphate (Pi)conditions.These effects of SLs have been shown to be associated with differential activation of the auxin and ethylene signalling pathways.

?Scope The present review highlights recent ?ndings on the activity of SLs as regulators of root development,in particular in response to low Pi stress,and discusses the different hormonal networks putatively acting with SLs in the root’s Pi response.

?Conclusions SLs are suggested to be key regulators of the adaptive responses to low Pi in the root by modu-lating the balance between auxin and ethylene signalling.Consequently,they impact different developmental pro-grammes responsible for the changes in root system architecture under differential Pi supply.

Key words:Strigolactones,root,phosphate,hormones,ethylene,auxin,root hairs,primary root,lateral root.

INTRODUCTION

Strigolactones (SLs)are now recognized as plant hormones (Gomez-Roldan et al.,2008;Umehara et al.,2008).These hor-mones were ?rst identi?ed over 40years ago as stimulants of parasitic plant (Striga and Orobanche )germination (Cook et al.,1966;reviewed by Xie et al.,2010).Later,their activity as stimulants of hyphal branching was discovered in the sym-biotic arbuscular mycorrhizal fungi (AMF;reviewed by Koltai et al.,2012).As plant hormones,SLs have been shown to act as long-distance branching factors,suppressing the outgrowth of pre-formed axillary shoot buds (e.g.Gomez-Roldan et al.,2008;Umehara et al.,2008).

SLs are terpenoid lactones derived from carotenoid (Matusova et al.,2005).Their presence has been demonstrated in a wide variety of plant species,including dicots,monocots and primitive plants,in which mixtures of several SL com-pounds have been found (reviewed by Xie et al.,2010;Liu et al.,2011;Proust et al.,2011).They are synthesized in a few different plant parts,but roots are considered to be the main site of SL biosynthesis (reviewed by Xie et al.,2010).There is also some evidence for the presence of the SL orobanchol in the xylem sap of arabidopsis (Kohlen et al.,2011),suggesting that root-derived SLs are transported to the shoot.The move-ment of SLs,their metabolites or other unknown secondary mes-sengers in the root-to-shoot direction might confer the observed reduction in shoot branching (reviewed by Dun et al.,2009).A number of SL-associated mutants have been found in several plant species.These include both SL-synthesis and SL-signalling mutants.Mutations in MAX1,a cytochrome P450,and in two carotenoid cleavage dioxygenase (CCD)enzymes (CCD7/MAX3and CCD8/MAX4)result in a hyper-branching phenotype and reduced levels of SLs,suggesting that they catalyse SL biosynthesis (e.g.Liang et al.,2010;Vogel et al.,2010;reviewed by Dun et al.,2009;Leyser,2009).Rice mutants in the iron-binding protein Dwarf27(D27)are also de?cient in SL levels (Lin et al.,2009).Recently,D27has been suggested to be a b -carotene isomer-ase that converts all-trans -b -carotene into 9-cis -b -carotene.The latter may serve as a substrate for cleavage by CCD7,fol-lowed by CCD8incorporation of oxygen:this produces carlac-tone,a compound with SL-like biological activities (Alder et al.,2012).The GRAS-type transcription factors NSP1and NSP2have been suggested to be putative regulators of the SL biosynthesis pathways in rice and Medicago (Liu et al.,2011).

Other mutants have been found to be insensitive to SLs.Mutations in MAX2confer an over-shooting phenotype (Stirnberg et al.,2002);this phenotype was not repressed by application of GR24(a bioactive,synthetic SL;Johnson et al.,1981;Umehara et al.,2008)and was not associated with reduced levels of the SL orobanchol (Kohlen et al.,2011).Hence,MAX2was suggested to be a component of SL signalling (Umehara et al.,2008)which encodes an F-box protein that might be part of the ubiquitin-mediated deg-radation of as-yet unknown protein targets (Stirnberg et al.,2007).Another gene associated with the SL response was shown to be Dwarf14(D14).Mutants in D14of both rice and arabidopsis showed a hyper-branching phenotype and in-sensitivity to SLs (Arite et al.,2009;Waters et al.,2012).Additional roles for SLs have been found in plants,includ-ing regulation of secondary growth (Agusti et al.,2011)and

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adventitious root formation(Rasmussen et al.,2012). Importantly,SLs are also involved in the regulation of root de-velopment:they have been shown to alter lateral root(LR)for-mation and root-hair(RH)length(Kapulnik et al.,2011a; Ruyter-Spira et al.,2011).

Phosphorus(P)is one of the essential macronutrients required by plants.It plays vital roles as a structural compo-nent of cellular macromolecules and in major metabolic pro-cesses.Inorganic phosphate(Pi)is the P form that is most readily accessible to plants.The availability of P varies consid-erably in soils(Maathuis,2009),whereas the concentration of Pi in soil solutions hardly ever exceeds10m M(Bieleski,1973). Plants have evolved strategies to cope with low P conditions. Roots are considered to be the main site of Pi absorption by the plant.Hence,among the functionally important structural changes undergone by plants under P deprivation are altera-tions in root development(Williamson et al.,2001; Lo′pez-Bucio et al.,2002;Sa′nchez-Caldero′n et al.,2005, 2006).Under low-Pi growth conditions,development of the root system architecture is altered by promotion of LR forma-tion and elongation,and inhibition of primary root(PR) growth;in addition,RH number and length increase.These changes are suggested to promote topsoil foraging and increase the root surface for absorption,thereby increasing the plant’s ability to absorb Pi(Lo′pez-Bucio et al.,2003;reviewed by Pe′ret et al.,2011).

Several studies have demonstrated a role for SLs in root and shoot responses to low Pi availability(Umehara et al.,2010; Kohlen et al.,2011;Ruyter-Spira et al.,2011;Mayzlish-Gati et al.,2012).The present review summarizes and discusses recent?ndings on the activity of SLs as regulators of root de-velopment,in particular in response to Pi conditions,and on the different hormonal networks putatively acting with SLs in the root’s Pi response.

ROLE OF SLs IN ROOT DEVELOPMENT Evidence from SL-mutant phenotypes and pharmacological studies suggests that SLs regulate the architecture of the root system.LR formation was shown to be negatively regulated by SLs in arabidopsis under conditions of suf?cient Pi nutri-tion(Kapulnik et al.,2011a).This is because mutants that are de?cient in SL response(i.e.max2)or biosynthesis(i.e. max3and max4)had more LRs than the wild type(WT) (Kapulnik et al.,2011a;Ruyter-Spira et al.,2011). Accordingly,treatment of seedlings with GR24affected LR formation(Kapulnik et al.,2011a;Ruyter-Spira et al., 2011).Moreover,an effect of exogenously supplied SLs on LR formation was found in the WT and SL-synthesis mutants,but was absent from the SL-response mutant;these results suggested that the effect of SLs on LR formation is mediated via the MAX2F-box(Kapulnik et al.,2011a; Ruyter-Spira et al.,2011).

SLs have also been shown to regulate RH elongation:GR24 treatment led to an increase in RH length in the WT and SL-de?cient mutants(max3and max4)but not in the SL-response mutant max2.Hence,SLs were suggested to have a positive effect on RH length,which is mediated via MAX2(Kapulnik et al.,2011a).

SLs have also been shown to be regulators of PR develop-ment.Under conditions of carbohydrate limitation,which usually lead to a reduction in PR length(Jain et al.,2007), GR24treatments at all concentrations had a positive effect, in a MAX2-dependent fashion,on PR elongation (Ruyter-Spira et al.,2011).Accordingly,under these condi-tions,the PR lengths of the SL-de?cient and SL-response mutants were shorter than those of the WT plant (Ruyter-Spira et al.,2011).This reduction in PR length was accompanied by a reduction in cell number in the PR meristem that could be rescued by application of GR24to SL-de?cient, but not SL-response mutants(Ruyter-Spira et al.,2011). SLs ARE MEDIATORS OF THE ROOT RESPONSE TO PHOSPHATE CONDITIONS Recently,SL biosynthesis and sensitivity have been shown to be important for the root’s ability to sense or respond to low-Pi growth conditions(Ruyter-Spira et al.,2011;Mayzlish-Gati et al.,2012).It seems that mutants that are?awed in SL bio-synthesis(e.g.max4)are unable to respond to low Pi condi-tions with respect to root architecture:induction of LR is reduced in the arabidopsis SL mutants compared with the WT under low-Pi growth conditions(Ruyter-Spira et al., 2011).Moreover,the SL mutants were de?cient in their ability to increase RH length and density under low Pi condi-tions relative to the WT,at least for the?rst96h post-germination under low-Pi growth conditions(H.Koltai, unpubl.res.;Mayzlish-Gati et al.,2012;Fig.1).

The number and length of RHs are thought to be directly associated with the plant’s ability to absorb nutrients from the soil(Sa′nchez-Caldero′n et al.,2005;reviewed by Gilroy and Jones,2000).Therefore,the lack of RH density increase in the SL mutants following germination suggests that they may suffer from reduced internal P levels.This suggestion is strengthened by the?nding that the expression of several Pi transporters is reduced in the SL mutants following germin-ation(Mayzlish-Gati et al.,2012).However,levels of P in the SL-insensitive mutant max2plants were found to be similar to those of the WT under diverse Pi conditions (Mayzlish-Gati et al.,2012),suggesting that even in the absence of an SL response,the plant can acquire P.On the other hand,despite the WT-like,low levels of P in the SL mutant under low Pi conditions,it was not able to alter its root development.Taken together,the results suggest that root sensing of,or response to,low Pi is dependent on the SL pathway and requires the activity of MAX2and WT levels of SLs.

With respect to the shoot,in both arabidopsis and rice,evi-dence has been brought showing that SLs contribute to regula-tion of the shoot architectural response to low-Pi growth conditions:at least one of the arabidopsis SLs(orobanchol) was detected in xylem sap and up-regulated under Pi de?-ciency,in correlation with the changes in shoot architecture observed under these conditions(Kohlen et al.,2011).In rice,tiller bud outgrowth in WT rice seedlings was inhibited, whereas root SL(2′-epi-5-deoxystrigol)levels increased in re-sponse to Pi de?ciency;the suppression of tiller bud outgrowth under low-Pi growth conditions was not evident in the SL-de?cient or insensitive mutants(Umehara et al.,2010;

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reviewed by Umehara,2011).Due to their proposed role in both shoots and roots,SLs might be considered mediators of root development and architecture in response to external growth conditions,in addition to their role in regulating shoot development.

However,it is likely that,in order to mediate plant response to Pi levels,SL pathways must be regulated by Pi levels.Indeed,SL production has been found to be induced under low Pi conditions in several plant species (e.g.Yoneyama

et al.,2007;Lo

′pez-Ra ′ez and Bouwmeester,2008;Kohlen et al.,2011).This induction was correlated with the inhibition of tiller or lateral bud outgrowth in WT rice and WT arabidop-sis (Umehara et al.,2010;Kohlen et al.,2011).As SLs are suggested to regulate the root’s response to Pi growth condi-tions,and possibly to internal P levels in the plant,the Pi-induced elevation of SL levels suggests a negative feedback loop between SLs and internal P levels,for ?ne regulation of the associated root response.

CROSS-TALK OF SLs WITH AUXIN AND

ETHYLENE TO CONTROL ROOT DEVELOPMENT UNDER DIFFERENT PHOSPHATE GROWTH CONDITIONS Other plant hormones are known to regulate root development (reviewed by Osmont et al.,2007).Moreover,other plant hor-mones are known to regulate plant responses to nutritional

conditions,including Pi de?ciency (reviewed by Lo

′pez-Bucio et al.,2002;Chiou and Lin,2011).Hence,it is likely that SLs exert their function via a carefully controlled network with other plant hormones.

It has been shown that polar auxin transport is modulated by SLs in the control of shoot branching,that SLs reduce the ba-sipetal transport of auxin and that in the presence of auxin,SLs enhance competition between two branches on a common stem.It was therefore suggested that SLs enhance competition between branches by dampening the shoot’s capacity for polar auxin transport (Crawford et al.,2010).On the other hand,in pea (Pisum sativum ),exogenously applied SL inhibited shoot bud outgrowth even when plants were decapitated and thus auxin-depleted,whereas SL application was not associated with blocking auxin transport in the bud.Application of SL was also able to reduce shoot branching in auxin-response mutants of arabidopsis.Moreover,contrary to the auxin trans-port model predictions,WT and SL-biosynthesis mutants of both pea and arabidopsis were capable of transporting exogen-ously supplied auxin.These results suggested that repression of bud outgrowth is due to auxin-dependent production of SLs,rather than to the effect of SLs on auxin transport from the buds (Brewer et al.,2009).Moreover,auxin has been shown to induce SL synthesis in the root via induction of CCD7and CCD8expression,indicating a feedback loop between auxin and SLs (reviewed by Beveridge and Kyozuka,2010).

In the root,SLs have been suggested to interfere with auxin-ef?ux carriers:only 2,4-D,a synthetic auxin that is not secreted by ef?ux carriers,restored normal root growth in the presence of SLs (Koltai et al.,2010).In agreement with this,the intensities of the auxin transporters PIN1-,PIN3-and PIN7-GFP decreased in the provascular tissue of the PR tip upon GR24treatment (Ruyter-Spira et al.,2011).Together,these results suggest that in the root,similar to the shoot,SLs have an effect on polar auxin transport.

An increase in local auxin levels or enhanced auxin sensitiv-ity in pericycle cells regulate LR formation through a mechan-ism involving PIN1(Benkova et al.,2003;reviewed by Pe

′ret et al.,2009).Treatment of seedlings with GR24resulted in a decrease in PIN1-GFP intensity in LR primordia,suggesting involvement of PIN1in the GR24-mediated reduction of LR formation.However,GR24application induced,rather than reduced,LR formation when auxin levels were increased by exogenous application.Under those conditions,there was no reduction in PIN1-GFP intensity (Ruyter-Spira et al.,2011).Based on these ?ndings,Ruyter-Spira et al.(2011)sug-gested that SLs,as modulators of auxin ?ux,might alter the auxin optima for LR formation:SLs reduced auxin import to

Col-0

max2-1Low Pi

max2-1

High Pi

Col-0

max4-1

max4-1

F I

G .1.Effects of high and low Pi conditions on root hair (RH)length and density of the WT,and max2-1and max4-1mutants.Examples of R

H phenotype in

Col-0,max2-1and max4-1under low (1m M )and high (2m M )Pi conditions at 48h post-germination.Scale bars ?500m m.

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the root under relatively low auxin levels,resulting in inhib-ition of LR formation.In contrast,under high auxin levels, this SL-mediated reduction allowed the generation of auxin optima,and induction of LR formation.Along the same lines,in both tomato and arabidopsis,an effect of GR24treat-ments on asymmetric root growth(Koltai et al.,2010; Ruyter-Spira et al.,2011)might be explained by asymmetric auxin distribution,or be a consequence of distorted expression of the PIN auxin ef?ux carriers(Ruyter-Spira et al.,2011). Similarly,decreased GUS staining from the auxin-response re-porter DR5-GUS in the aerial parts of GR24-treated plants might indicate SL reduction of auxin sensitivity or levels (Ruyter-Spira et al.,2011).

Another indication that auxin is downstream of SLs in the signal transduction pathway comes from an examination of mutants’root responses.SL signalling was shown not to be ne-cessary for the RH elongation induced by auxin,because the SL-insensitive mutant max2was responsive to auxin. However auxin signalling was needed,at least in part,for the RH-elongation response to SLs:the auxin-receptor mutant tir1-1(Dharmasiri et al.,2005)showed reduced sensi-tivity to SLs relative to the WT(Lo′pez-Bucio et al.,2003; Kapulnik et al.,2011b).

Root development,including a positive effect on RH elong-ation and a negative one on LR formation,has been shown to be regulated by ethylene as well(reviewed by Lo′pez-Bucio et al.,2002).Accordingly,the involvement of ethylene signal-ling in the SL response has been suggested under suf?cient-Pi growth conditions.This suggestion was based on the markedly reduced SL response in the ethylene-signalling mutants etr and ein,on the negative effect of aminoethoxyvinylglycine (an ethylene-synthesis inhibitor)on the RH response to SLs,and on the ability of SLs to induce transcription of the 1-aminocyclopropane-1-carboxylic acid(ACC)synthases, involved in ethylene biosynthesis(Kapulnik et al.,2011b). Accordingly,SLs were shown to induce ethylene biosynthesis in seeds of the parasitic plant Striga,leading to their germin-ation(Sugimoto et al.,2003).Therefore,the effect of SLs on the plant may involve ethylene biosynthesis.

Ethylene has been suggested in several studies to be involved in the response to low Pi(e.g.Lei et al.,2011; Nagarajan et al.,2011).Analysis of the root architecture of ethylene-signalling mutants and ACC-treated plants suggested that ethylene is involved in the process of RH formation and meristem exhaustion activated by Pi starvation,but not in the promotion of LR formation under these conditions (reviewed by Sato and Miura,2011).In other studies,it was suggested that low P does not act via ethylene in its effect on RH density(Ma et al.,2001).Indeed,ethylene was shown not to mediate the low-Pi response of SLs,at least with respect to RH density:ethylene was not able to compen-sate for the de?ciency in the response of max2to low Pi. Therefore,the MAX2-regulated RH-density response to low Pi conditions is suggested to be downstream or independent of the ethylene pathway(Mayzlish-Gati et al.,2012). However,under Pi deprivation,addition of indole-3-acetic acid(IAA)to SL-insensitive and SL-biosynthesis mutant roots led to complementation of the mutants’phenotypes to that of the WT,suggesting that auxin is part of the SL-response pathway to low-Pi growth conditions(Mayzlish-Gati et al.,2012).Indeed,auxin signalling is associated with alterations in root system architecture as a result of Pi depriv-ation,whereas Pi-deprived plants are more sensitive to exogen-ous auxin than Pi-nourished plants with regard to the induced formation of LR and arrest of PR growth(reviewed by Lo′pez-Bucio et al.,2002;Chiou and Lin,2011). Moreover,under these conditions of Pi-deprivation,max2 also displayed reduction rather than induction of TIR1tran-scription(Mayzlish-Gati et al.,2012).In the WT,the auxin pathway and induction of TIR1transcription were suggested to play a fundamental role in the modi?cations of root architec-ture by P availability(Lo′pez-Bucio et al.,2003;Pe′rez-Torres et al.,2008).Thus,the de?ciency in the response of the max2 mutant to low Pi might be associated with a reduction in TIR1 transcription in comparison with the WT(Mayzlish-Gati et al., 2012).However,due to the relatively high levels of auxin in the max2mutants(Bennett et al.,2006),this lack of induction is probably not directly associated with reduced activity of the auxin pathway.Accordingly,the tir1mutant showed a reduced response to low Pi in comparison with the WT(Pe′rez-Torres et al.,2008),which could not be restored by GR24application. Hence,the de?ciency in the response of tir1to low Pi is prob-ably downstream of the SL signalling pathway(Mayzlish-Gati et al.,2012).

Taken together,these studies suggest that different SL-related hormonal pathways are activated under different Pi conditions(Fig.2).Under conditions of Pi suf?ciency, the SL pathway,through MAX2,might activate ethylene

High Pi Low Pi

F I G.2.Schematic illustration of the hormonal pathways activated by SLs in re-sponse to different Pi growth conditions.Under suf?cient Pi,the SL pathway,via MAX2,is suggested to act mainly through the ethylene pathway(Kapulnik et al., 2011b).This response is suggested to be mediated by ethylene-insensitive(EIN) and ethylene-resistant(ETR)proteins(Kapulnik et al.,2011b;Koltai,2011). Auxin synthesis,transport(including PIN Formed protein(PIN)expression) and signalling are positively affected by ethylene signalling(Stepanova and Alonso,2009,and references therein).In addition,SLs have been suggested to dampen auxin transport(Crawford et al.,2010).Hence,the auxin pathway may be activated either by the ethylene pathway or directly by SLs,to regulate root development for suf?cient-Pi growth conditions.However,under conditions of Pi depletion,during the?rst few hours of seedling development,the SL pathway,through MAX2,is suggested to activate mainly the TIR1-dependent auxin signalling pathway(Mayzlish-Gati et al.,2012),thereby regulating root de-velopment to suit those growth conditions.

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biosynthesis as well as the auxin pathway,to regulate root de-velopment(Koltai,2011).Under conditions of Pi depletion, the SL pathway,through MAX2,might mainly activate auxin signalling,and thus regulate root development such that it will be suited to those growth conditions(Fig.2). Accordingly,the auxin and ethylene signalling pathways have been suggested to be differentially activated under diverse Pi growth conditions and to regulate different aspects of the root response to these conditions.It was suggested that acclimation of the root system to P de?ciency is achieved by changing ethylene sensitivity(Ma et al.,2003).On the other hand,reduced Pi availability was shown to increase auxin sensitivity and to lead to induction of TIR1transcription, thereby conferring a Pi-deprivation root response associated with LR development(Lo′pez-Bucio et al.,2003;Pe′rez-Torres et al.,2008).Moreover,Schmidt and Schikora(2001) suggested that the signal from a P-de?ciency-speci?c stress might act directly on components of an ethylene-independent pathway to confer RH elongation under conditions of Pi de-privation.Accordingly,SL may be one of the signals of P-de?ciency stress,and activation of its signalling pathway might be an important component of the root’s response to low-Pi growth conditions,when it acts mainly via auxin signalling.

CONCLUDING REMARKS

An increasing number of studies are suggesting the involve-ment of SLs in shoot and root development.On the one hand,shoot-derived auxin has been shown to positively regu-late the biosynthesis of root-derived SLs.On the other,SLs have been shown to contribute to the regulation of both shoot and root architecture in response to Pi growth conditions as well.

In roots,developmental SL-regulation might be carried out via the activation of alternative signalling pathways:under conditions of Pi suf?ciency,SLs act mainly through the ethyl-ene signalling pathway,and under low Pi conditions,they act mainly through the auxin pathway.This may position SLs as an important element in the plant’s ability to sense or respond to low Pi conditions,and modify shoot and root growth and development accordingly.SLs might adjust the balance between auxin and ethylene signalling pathways to ac-tivate different developmental programmes in response to changes in soil Pi,thereby controlling their own biosynthesis via a positive feedback loop:increased SL levels under low Pi conditions might lead to increased sensitivity to shoot-derived auxin,and therefore to increased SL biosynthesis in roots under these conditions.

Moreover,Pi signalling and the plant’s response are known to rely on local and systemic signalling in both root and shoot, and to require?ne-tuned communication between them (reviewed by Chiou and Lin,2011).Perhaps some of the shoot–root communication in response to Pi conditions is con-veyed via the SL-biosynthesis and signalling systems.Several genes are known to act in the plant response to Pi starvation. Some of them,such as those encoding PDR2(Phosphate De?ciency Response2),LPI(Low Phosphorus Insensitive) and LPR(Low Phosphate Root),might be acting locally,at the root tip,to regulate Pi response(Lo′pez-Bucio et al.,2005;Sa′nchez-Caldero′n et al.,2006;Svistoonoff et al., 2007;Ticconi et al.,2009;reviewed by Chiou and Lin, 2011).In contrast,the gene encoding PHR1(Phosphate Starvation Response1)acts systemically to positively regulate miR399expression under Pi starvation(Chiou and Lin,2011, and references therein).Studies examining SL involvement in the activity of such genes may promote insight into the local and/or systemic activity of SLs in both root and shoot under Pi starvation.Moreover,because LPR1has been suggested to participate in vesicular targeting of auxin transporters and to have a positive role in pericycle cell activation to form LR primordia and RH elongation(Lo′pez-Bucio et al.,2005), interaction of this protein with the SL pathway might explain the positive effects of SLs on RH elongation(Kapulnik et al.,2011a)and LR formation under low Pi conditions (Ruyter-Spira et al.,2011).

Another aspect of the role of SLs in roots is their involve-ment in signalling in the rhizosphere.SLs were initially iden-ti?ed as signalling molecules that are exuded from plants and necessary for parasitic plant germination.They are also known to be important signals for hyphal branching in plant-symbiotic AMF(reviewed by Xie et al.,2010;Koltai et al., 2012).Interestingly,as AMF promote the plant’s ability to acquire Pi(e.g.Bucher,2007),and because SL secretion and production have been shown to increase under low Pi condi-tions(Yoneyama et al.,2007),SLs may bene?t plants under Pi-deprived conditions by promoting the mycorrhizal associ-ation,in addition to their role as regulators of root development.However,the agricultural potential of SLs as modulators of plant development,and perhaps as a means of promoting AMF symbiosis,remains largely unexplored.Site, timing and concentrations of SL application still have to be optimized for their practical application.

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●什么是人类生长激素HGH？ 人类生长激素为Human Growth Hormone，生长激素(Growth Hormone)是一种由脑下垂体腺(Pituitary Gland)分泌，能刺激生长的物质。人的身高、体态、器官组织的发育，健全与否皆由生长荷尔蒙控。一直到二十五岁，成长完成，其高峰在血中含量600mg。以后逐年递减，60-70岁时约只剩15%。有些人如果偏食，营养摄取不均衡，可能在40-50时，其含量就只剩15%。故在外貌上比同年龄的人显得苍老、憔悴。 ●HGH分泌随年龄而减少的原因有二： l、自体回馈循环作用，当身体内IGF-l减低时会传送讯号到脑下垂体，使它分泌较多的HGH，自体回馈循环功能随年龄而减退。成长期生长激素分泌不足影响发育甚大。 2﹒HGH的分泌，受到脑部下视丘Hypothalamus所分泌的两种贺尔蒙的影响而调节：a) Growth Hormone releasing Hormone (GHRH)：刺激HGH分泌。一生浓度都相同。b) Somatostatin (SKIF)：抑制SGH的分泌，每天有波段性减少,此时即HGH 分泌之高峰波段,但这种Somatostatin随年龄增长而增加,使HGH分泌渐渐减弱。 ●为什么要补充生长激素？ 如果能让脑下垂体腺再恢复功能，分泌充沛的生长激素，虽较25岁时的最高略差，但已足够滋润各器官组织，让功能已显疲态，或是在年少时发育不良的器官组织，再次健全。故有肺疾、胃病、胆固醇高、血糖异于常人的患者，皆因生长激素的充沛而获改善、痊愈。而对于男性睪丸和女性卵巢的滋润，进而促进雄性荷尔蒙和女性荷尔蒙的活泼，增加男性雄壮和女性的魅力。男性的啤酒肚(中广身材)、女性的小腹、大腿赘肉、双下巴皆可由雄性和雌性荷尔蒙的均衡，使体内脂肪不易聚集，而获匀称、健美的身材，尤其产后女性，肌肉松弛，更需靠生长激素帮助，恢复坚挺身材，富弹性的肌肤，停经较早的妇女(如45-50)会因卵巢功能恢复、加强而使经期再次恢复而受益-骨质疏松缓，全身不会酸痛；干皱的皮肤恢复亮丽。 5岁-30岁的男女青少年，如较常人矮小，可由生长激素的充裕，刺激骨骼组织，增进干骨的发育，逐月增高。同时，加强肌肉的发育，使平胸凸出，而获得凹凸有致的身材。但是，切记，生长激素每夜由11时至清晨4时血液循环系统至全身。如果熬夜、或是错过上述时间睡眠，则无法获得人体自然分泌的生长激素，无法改善身体受损的情况，所以更需要藉外来的HGH Enhancer(生长激素促进剂)来补充。HGH Enhancer(生长激素促进剂)可刺激脑下垂分泌充沛的生长激素。此增多的荷尔蒙属自体制造，分泌、无排斥性，不会引起细胞组织的变化，产生癌症的恐惧性副作用。因年老引发的诸种慢性病，如视力减退，骨质疏松、心脏机能障碍、肥胖、手脚麻痹、耳鸣、心悸、疲倦等症，都可获得显著的改善。

聚乙二醇化生长激素释放激素的研究进展 (8)

2012年5月第19卷第14期·综述· 生长激素释放激素（growth hormone-releasing hormone，GHRH）又称生长激素释放因子（growth hormone-releasing factor，GRF），它是由下丘脑分泌的一种肽类激素，具有促进垂体促生长素细胞合成和释放生长激素（growth hormone，GH）的作用。临床上可以用来治疗矮小症、HIV相关的脂肪营养不良、创伤等疾病。然而GHRH应用到临床上的最大不足就是体内半衰期比较短（一般10～20min）[1]。为了延长GHRH在体内的半衰期，减少频繁用药给患者带来的不适，须对GHRH进行修饰，以期达到半衰期显著延长，免疫原性有所降低同时副作用相对较小。为此，本文主要综述了GHRH 以及GHRH长效修饰的研究进展，尤其是PEG修饰GHRH 的最新进展。 1生长激素释放激素的研究概况 GHRH是由下丘脑分泌的一种肽类激素，具有促进垂体促生长素细胞合成和释放GH、IGF-1的作用，目前已被广泛应用到临床。 1.1GHRH的发现 早在20世纪60年代，人们就已经注意到人体内GHRH 的存在，由于技术限制，一直没有得到证实。直到1982年Rivier J等[2]及Guillemin R等[3]分别从引起肢端肥大症的胰腺肿瘤组织中分离提纯出3种GHRH，同时鉴定了相应氨基酸数目分别为44、40及37，分别命名为GHRH1-44NH2、GHRH1- 40 OH、GHRH1-37NH2。其中GHRH1-44NH2的分子结构见图1。 51015 Tyr-Ala-Asp-Ala-Ile-Phe-Thr-Asn-Ser-Tyr-Arg-Lys-Val-Leu-Gly- 202530 Gln-Leu-Ser-Ala-Arg-Lys-Leu-Leu-Gln-Asp-Ile-Met-Ser-Arg-Gln- 3540 Gln-Gly-Glu-Ser-Asn-Gln-Glu-Arg-Gly-Ala-Arg-Ala-Arg-Leu-NH2 图1GHRH1-44NH2的分子结构 1.2GHRH结构与活性的关系 目前已经证实体内GHRH主要有3种形式，即GHRH1-44NH2、GHRH1-40OH、GHRH1-37NH2，其中以GHRH1-40OH大量存在，它 聚乙二醇化生长激素释放激素的研究进展 王永1刘沐荣2万海同1 1.浙江中医药大学生物工程学院，浙江杭州310053； 2.杭州北斗生物技术有限公司，浙江杭州310011 [摘要]生长激素释放激素（growth hormone-releasing hormone，GHRH）又称生长激素释放因子（growth hormone-releas-ing factor，GRF），是由下丘脑分泌的一种肽类激素，具有促进垂体促生长素细胞合成和释放生长激素（growth hor-mone，GH）的作用，临床上可以用来治疗矮小症、HIV相关的脂肪营养不良、代谢综合征、艾滋病、创伤等疾病。然而GHRH应用到临床上的最大不足就是体内半衰期比较短（一般10～20min）。为了延长GHRH在体内的半衰期，减少频繁用药给患者带来的不适，须对GHRH进行修饰，以期达到半衰期显著延长，免疫原性有所降低。为此，本文主要综述了GHRH以及GHRH长效修饰的研究进展，尤其是PEG修饰GHRH的最新进展。 [关键词]生长激素释放激素；生长激素；聚乙二醇化；修饰 [中图分类号]Q81[文献标识码]A[文章编号]1674-4721（2012）05（b）-0013-04 The research of development on Pegylation of growth hormone-releasing hormone WANG Yong1LIU Murong2WAN Haitong1 1.Biological Engineering Institute of Zhejiang Chinese Medical University,Hangzhou310053,China; 2.BIODOOR Biotechnology Co.Ltd of Hangzhou City in Zhejiang Province,Hangzhou310011,China [Abstract]Growth hormone releasing hormone(GHRH)also known as growth hormone releasing factor(GRF),a peptide hormone,is secreted by the hypothalamus and has the function of promoting the synthesis and release of growth hormone. Although it can be used to treat short stature,HIV-associated lipodystrophy,syndrome X,AIDS,trauma and other diseases in clinic,however,the biggest shortcoming of GHRH is the short half life in vivo(usually10-20minutes).In order to ex-tend the half life of GHRH in vivo,reduce the dosing frequency which bring some discomfort to the patients,some mea-sures should be taken to modify the GHRH.This paper mainly reviews the research development of GHRH,polyethylene glycol as well as the modification of GHRH,especially the pegylation of GHRH. [Key words]Growth hormone releasing hormone;Growth hormone;Pegylation;Modification

生长激素激发试验在矮小儿童中的应用分析

生长激素激发试验在矮小儿童中的应用分析 发表时间：2016-03-22T16:58:28.153Z 来源：《中国慢性病预防与控制》2015年8月第2期供稿作者：颜美玲张英华张丹 [导读] 湘潭市中心医院生长激素激发试验是评价患儿垂体生长激素分泌和生长激素缺乏症的主要依据。 （湘潭市中心医院湖南湘潭 411100） 【摘要】目的：探讨生长激素激发试验在矮小儿童病因检查的临床价值。方法：对22例符合矮小症标准的儿童应用左旋多巴、精氨酸进行两种药物联合激发试验，在用药前0分钟、用药后30、45、60、90、120分钟分别抽血进行血清生长激素检查。结果：应用两种药物进行联合激发，GH峰值主要出现在30~90分钟。结论：试验过程中基本无明显副反应，小朋友容易接受，安全可靠，值得临床广泛推广应用。【关键词】生长激素激发；矮小儿童 【中图分类号】R584 【文献标识码】A 【文章编号】1004-6194（2015）02-0343-01 生长激素激发试验是评价患儿垂体生长激素分泌和生长激素缺乏症的主要依据。而生长激素的分泌是呈不规则间断性分泌，判断生长激素是否缺乏应该选择两种以上药物进行激发试验，任何一种药物进行激发试验，都存在假阴性的可能。本文对22例身材矮小患儿使用左旋多巴与精氨酸两种药物进行生长激素联合激发试验。现报告如下： 1 对象与方法 1.1对象 均在我院儿童保健门诊就诊的身材矮小患儿，符合在相似生活环境下，个体身高低于同年龄、同种族正常人群平均身高2个标准差（-2SD），或低于第3百分位数（-1.88SD），骨龄落后2年以上者。男性16例，女性6例，年龄3.5岁~14岁。 1.2方法 进行生长激素药物激发试验者要求在没有感冒生病的情况下，在精神状态良好的情况下进行。所有患者在清晨、空腹状态下，使用左旋多巴与精氨酸两种药物联合应用，开始进行操作。用药前检测空腹血糖，血糖正常的情况下进行下一步方案。先抽一次空腹静脉血进行0分钟生长激素检测，继而口服左旋多巴（使用剂量10mg/kg，最大剂量不超过500mg），口服后立即静脉快速滴注精氨酸（按0.5g/kg用生理盐水稀释成10%的溶液，最大剂量不超过30mg）静脉，30分钟内滴完。滴完药物后在30、45、60、90、120min各抽血一次，共6次静脉血进行生长激素检测，血液标本立即送检，标本送检验科实验室检测。分离血清，采用全自动化学发光法检测血清生长激素。 1.3 诊断标准 以联合药物激发试验的生长激素峰值作为标准，峰值≧10ng/ml,提示生长激素分泌正常，为GH不缺乏；10ng/ml>峰值≧5ng/ml，提示生长激素部分缺乏，为部分GH缺乏（PGHD）；峰值<5ng/ml,提示生长激素完全缺乏，为完全GH缺乏（GHD）。 2 结果 2.1生长激素激发试验不同时间所测得的不同数据水平如下 各时间段生长激素激发后的生长激素水平（ng/ml） 统计采用SPSS19.0统计软件，结果以均数±标准差见表1 以上数据表明两种药物联合生长激素激发试验后，在不同的时间所得生长激素实验室数据2.2生长激素激发试验峰值出现时间生长激素激发试验后30、60、90分钟分别有6、7、5例峰值，为27.2%、31.8%、22.7%，所测得的峰值以30~90min为主；45、120分钟均有2例，占9.1%，其中有1例患儿峰值在45min，为10.08ng/ml稍高于异常值10ng/ml，见表2： 3 讨论 儿童身材矮小的病因很多，与遗传、营养、疾病、生活环境、心理因素、宫内发育等因素有关，在排除疾病、遗传等病理因素外，儿童均衡营养、合理睡眠、精神心理以及体育锻炼等各个方面是值得非常重视的。针对身材矮小的儿童，应尽早寻找病因，早期发现，早期干预，改善终身高。 生长激素是垂体前叶嗜酸细胞分泌的胎类激素，由191个氨基酸残基组成。受下丘脑分泌的生长激素释放激素（GHRH）和生长激素释放抑制激素（GHIH）的双重调节【1】。儿童垂体分泌的生长激素在一天的时间内呈不规则的间断分泌状态，除夜间深睡眠状态下有 1~2小时的分泌高峰外，在其余时间均呈低水平分泌状态。当然生长激素亦受药物、睡眠、饮食、运动等的影响。所以在常态下，一次随机

生长激素系列谈

生长激素系列谈 目录： 1. 什么是生长激素 2. 生长激素是美国FDA批准唯一用于促进儿童生长的药物 3. 生长激素用量及疗程 4. 生长激素治疗疗效分析 5. 生长激素发展史 6.生长激素优缺点对比 01 什么是生长激素 生长激素（GH）是由垂体前叶生长激素细胞产生的一种蛋白激素。生长激素对正常的生长是必须的，除有增加身高的作用外，对心脏、肾脏等的功能和皮肤、内脏、骨骼、肌肉、性腺等生长发育均起到重要作用；对人体糖、脂肪及蛋白质三大代谢均有较大的影响。 虽然生长激素缺乏者，不像胰岛素缺乏引起的糖尿病一样，不用胰岛素会立即出现生命危险，但也会引起矮小、骨质疏松、肌肉发育不良、易患心血管疾病、性发育不良、易衰老等一系列异常表现。 02 重组人生长激素适应症

重组人生长激素是美国FDA批准唯一用于促进儿童生长的药物。 全球药品审查最严格的机构——美国药品食品管理局（FDA），批准生长激素适应症1996 先天性卵巢发育不全2001 小于胎龄儿（SGA）2006 SHOX基因缺少但不伴GHD患儿 1985 儿童生长激素缺乏症（GHD）1997 成人生长激素缺乏2003 特发性矮身材（ISS） 近年来还发现，rhGH在抗衰老、减肥治疗方面取得了较突出的疗效，荷兰的一项研究提示，rhGH对智力发育有一定促进作用。 生长激素是分子量约22KD的蛋白质，如果口服，会被分解。 目前rhGH使用方法与胰岛素类似，冻干粉剂应用厂家配送的注射用水溶解后，应用一次性注射器注射。 水剂可用隐针电子笔注射。由于孩子看不到针头减少恐惧感，5mm电子笔针头非常细，77%的孩子不会有疼痛感。短效生长激素每晚睡前1小时左右注射一次。 长效一周一次的生长激素，每周固定一天注射即可。 还有家长问道，某某增高药吃了能不能长高？ 卫生部批准的保健食品功能中并没有增高这一项，保健品中含有的成分如果刚好是小朋友缺少的可能可以起到长高的效果，但是，由于每个小朋友出现生长迟缓的原因不同，是否缺少以及缺乏哪一种营养素，需要到正规医院进行化验检测，针对具体缺乏的某项进行补充是最好的，盲目过量补充对身体不一定有益。这些营养物质其实和我们日常生活中所吃的食物营养一样，单靠它们治疗矮小，是不可能奏效的。 03 生长激素用量及疗程 推荐的参考用量：生长激素的剂量范围较大，应根据需要和观察到 的疗效进行个体化调整。目前国内常用剂量是0.1-0.15I U/k g·d，每周0.23-0.35m g/k g；对青春发育期患儿、T u r n e r患儿、小于胎龄儿、特发性矮身材和某些部份性生长激素缺乏症患儿的应用剂量为0.15-0.20I U／（㎏.d）每周0.35-0.46（㎎.㎏）（注：W H O标注生长激素1㎎=30U），一般不超过0.2u/k g/d。

激素定义、分类、临床应用及注意事项副作用

激素定义、分类、临床应用及注意事项副作用 广义定义：激素类药物就是以人体或动物激素（包括与激素结构、作用原理相同的有机物）为有效成分的药物。狭义定义：通常，在医生口中的“激素类药物”一般情况下在没有特别指定时，是“肾上腺糖皮质激素类药物”的简称。其他类激素类药物，则常用其分类名称，如“雄性激素”、“胰岛素”、“生长激素”等。 1 分类 激素类药物可以分为：糖皮质激素、肾上腺皮质激素、去甲肾上腺激素、孕激素、雌激素、雄激素等。 该类药物常见使用方式：静脉使用、口服、外用及其他。常见剂型：注射粉针、水针、胶囊、片剂、霜剂、膏剂、气雾剂。 依不同方法分类若按药物类别来划分，共可分为以下五类： 1、肾上腺皮质激素类:包括促肾上腺皮质激素. 糖皮质激素.盐皮质激素. 2、性激素类:包括雌激素类.孕激素类.雄激素类.同化激素类.促性腺激

素类 3、甲状腺激素类:包括促甲状腺激素.甲状腺激素类. 4、胰岛素类: 包括长效胰岛素类.中效胰岛素类.短效胰岛素类. 5、五垂体前叶激素类:包括生长激素类.生长抑素类.生长激素释放激素(GHRH)及类似药.促肾上腺皮质激素释放激素类. 其中，第一类，肾上腺皮质激素类，是指肾上腺皮质部分泌多种激素的总称。 肾上腺是位于肾脏上面的一个内分泌腺体，左、右各一，重约5g，左肾上腺近似半月形，右肾上腺呈三角形。肾上腺可划分为皮质部分与髓质部分。其中，皮质部分分泌三大类激素：盐皮质激素、糖皮质激素、及少量性激素。所以，男性也会分泌雌性激素，女性也会分泌雄性激素。分泌紊乱时，会导致第二性征紊乱。 肾上腺皮质激素类，若按种类划分： （1）盐皮质激素：由皮质的球状带合成分泌，以醛固酮和去氧皮质酮为代表，对水盐代谢有一定的影响，故称盐皮质激素。较少用于药物。 （2）糖皮质激素类：由皮质的束状带合成和分泌，主要影响糖和蛋白质等代谢，且能对抗炎症反应，而对水盐代谢影响较小，临床应用较广。主要药物以氢化可的松为代表，一般所说的“皮质激素”即指这一类。人工合成的糖皮质激素类药，比天然激素具有的抗炎作用更强，对水盐代谢影响更小的优点，因而在应用上更为重要。常用的药有泼尼松、氢化泼尼松和氟美松。

怎样提高生长激素(内容清晰)

怎样提高生长激素？ 我们都知道，身高对于一个人来说是很重要的，很多工作都会挑身高。生长激素是一种可以帮助人体发育的物质，正常情况下人体内都不会缺少，但是因为先天因素的影响或者是后天疾病的威胁，结果导致身体缺乏足够的生长激素，进而引发不长个子的情况。那么，如何才能提高生长激素呢? 1蛋白质 2睡眠 3锻炼 是不是很简单?蛋白质含氨基酸，有助于身体组织的修复和生长。人体生长激素是一种构建组织的荷尔蒙，是由脑下垂体产生的。它促使身体发展，组织修复，把储存的脂肪转换为能量，所有这些功能都需要氨基酸帮助。

这也是构建身体肌肉块不能缺少蛋白质的原因。当高血糖碳水化合物(被认为是坏淡水化合物)释放胰岛素(一种说服身体储存脂肪的荷尔蒙)时，蛋白质释放胰高血糖素让身体转变成脂肪燃烧器。 动物和植物蛋白质来源相结合对身体健康是最好的。如果仅仅依靠动物蛋白质来源，就需要消费大量动物肉类脂肪。因此，健康专家建议除此之外，还应该消费植物类蛋白(如大豆)。研究发现赖氨酸(动物蛋白里最丰富)会增加身体坏胆固醇水平，而精氨酸(植物蛋白里最丰富)可以减少它们。大豆蛋白的赖氨酸含量少，因此有助于降低身体胰岛素生产，并增加胰高血糖素的产量。经常消费大豆蛋白有助于提高身体新陈代谢能力，它促使身体由储存脂肪状态转变为燃烧脂肪。 这是否意味着我们应该全部采用植物蛋白?肯定不是。重要的是要保持饮食中蛋白质，好碳水化合物和必需脂肪酸的均衡。最佳比例是30%蛋白质，40-45%低血糖良好碳水化合物，以及 25-30%的脂肪酸。 缺乏睡眠也会导致我们发胖。失眠释放压力激素皮质醇，刺

激食欲并降低新陈代谢。这也是睡眠不仅对体重控制很重要，而且还对释放人体生长激素很重要的原因所在。研究发现，人体生长激素是在睡眠的第三和第四阶段分泌，也就是进入深度睡眠后的第1或2个小时。因此，如果不能获得深度睡眠，就等于破坏了身体修复和细胞再生能力。除非进入深度睡眠状态，否则生长激素难以有效释放。 锻炼是一种抗老化有力的工具。但不是所有运动都有助于释放生长激素。研究发现，只有在肌肉持续运动并造成疲劳的情况下才会获得生长激素，此外，运动密度还要保持正确水平。

糖皮质激素的副作用,要懂得避开负面影响

糖皮质激素的副作用，要懂得避开负面影响 糖皮质激素被人体有着非常多的功能，比如能够治疗败血症，对抗SARS，能够调节血糖含量等，所以越来越多的被人类利用，但据专家介绍，如果使用不当的话，这种激素一样会有副作用。 ★1、诱发或加重感染 糖皮质激素可抑制机体的免疫功能，且无抗菌作用，故长期应用常可诱发感染或加重感染，可使体内潜伏的感染灶扩散或静止感染灶复燃，格外是原有反抗力下降者，如肾病综合征、肺结核、再生障碍性贫血病人等。由于用糖皮质激素时病人往往自感觉良好，掩饰感染进展的症状，故在决定采纳长程治疗之前应先检察身体，排除潜伏的感染，应用过程中也宜进步警惕，必要时需与有效抗菌药适用，格外注意对潜伏结核病灶的防治。

★2、物质代谢和水盐代谢紊乱 长期大量应用糖皮质激素可引起物质代谢和水盐代谢紊乱，出现类肾上腺皮质功能亢进综合征，如浮肿、低血钾、高血压、糖尿、皮肤变薄、满月脸、水牛背、向心性肥胖、多毛、痤疮、肌无力和肌萎缩等症状，一般不需格外治疗，停药后可自行消退。但肌无力恢复慢且不完全。低盐、低糖、高蛋白饮食及加用氯化钾等措施可减轻这些症状。此外，糖皮质激素由于抑制蛋白质的合成，可延缓创伤病人的伤口愈合。在儿童可因抑制生长激素的分泌而造成负氮平衡，使生长发育受到影响。 ★3、心血管系统并发症 长期应用糖皮质激素，由于可导致钠、水潴留和血脂升高，可诱发高血压和动脉粥样硬化。

★4、消化系统并发症 Gucocorticoid能刺激胃酸、胃蛋白酶的分泌并抑制胃粘液分泌，降低胃粘膜的反抗力，故可诱发或加剧消化性溃疡，糖皮质激素也能掩饰溃疡的初期症状，以致出现突发出血和穿孔等严重并发症，应加以注意。长期使用时可使胃或十二指肠溃疡加重。在适用其他有胃刺激作用的药物（如aspirin、indometacin、butazolidin）时更易发生此副作用。对少数患者可诱发胰腺炎或脂肪肝。 ★5、白内障和青光眼 糖皮质激素能诱发白内障，全身或局部给药均可发生。白内障的产生可能与糖皮质激素抑制晶状体上皮Na+-K+泵功能，导致晶体纤维积水和蛋白质凝集有关。糖皮质激素还能使眼内压升高，诱发青光眼或使青光眼恶化，全身或局部给药均可发生，眼内压升高的原因可能是由于糖皮质激素使眼前房角小梁网结构 的胶原束肿胀，阻碍房水流通所致。

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