Gibberellin （GA） 2-oxidase plays a key role in the GA catabolic pathway through 2β-hydroxylation.In the present study,we isolated a CaMV 35S-enhancer activation tagged mutant,H032.This mutant exhibited a dominant d...Gibberellin （GA） 2-oxidase plays a key role in the GA catabolic pathway through 2β-hydroxylation.In the present study,we isolated a CaMV 35S-enhancer activation tagged mutant,H032.This mutant exhibited a dominant dwarf and GA-deficient phenotype,with a final stature that was less than half of its wild-type counterpart.The endogenous bioactive GAs are markedly decreased in the H032 mutant,and application of bioactive GAs （GA3 or GA4） can reverse the dwarf phenotype.The integrated T-DNA was detected 12.8 kb upstream of the OsGA2ox6 in the H032 genome by TAIL-PCR.An increased level of OsGA2ox6 mRNA was detected at a high level in the H032 mutant,which might be due to the enhancer role of the CaMV 35S promoter.RNAi and ectopic expression analysis of OsGA2ox6 indicated that the dwarf trait and the decreased levels of bioactive GAs in the H032 mutant were a result of the up-regulation of the OsGA2ox6 gene.BLASTP analysis revealed that OsGA2ox6 belongs to the class III of GA 2-oxidases,which is a novel type of GA2ox that uses C20-GAs （GA12 and/or GA53） as the substrates.Interestingly,we found that a GA biosynthesis inhibitor,paclobutrazol,positively regulated the OsGA2ox6 gene.Unlike the over-expression of OsGA2ox1,which led to a high rate of seed abortion,the H032 mutant retained normal flowering and seed production.These results indicate that OsGA2ox6 mainly affects plant stature,and the dominant dwarf trait of the H032 mutant can be used as an efficient dwarf resource in rice breeding.展开更多
Floral initiation is a major step in the life cycle of plants, which is influenced by photoperiod, temperature, and phytohormones, such as gibberellins （GAs）. It is known that GAs promote floral initiation under sho...Floral initiation is a major step in the life cycle of plants, which is influenced by photoperiod, temperature, and phytohormones, such as gibberellins （GAs）. It is known that GAs promote floral initiation under short-day light conditions （SDs） by regulating the floral meristem-identity gene LEAFY （LFY） and the flowering-time gene SUPPRESSOR OF OVEREXPRESSION OF CO 1 （SOC1）. We have defined the role of the auxin signaling component INDOLE-3-ACETIC ACID 7 （IAA7）/AUXIN RESISTANT 2 （AXR2） in the regulation of flowering time in Arabidopsis thaliana. We demonstrate that the gain-of-function mutant of IAA7/AXR2, axr2-1, flowers late under SDs. The exogenous application of GAs rescued the late flowering phenotype of axr2-1 plants. The expression of the GA20 oxidase （GA2Oox） genes, GA2Ooxl and GA2Oox2, was reduced in axr2-1 plants, and the levels of both LFY and SOC1 transcripts were reduced in axr2-1 mutants under SDs. Furthermore, the overexpression of SOC1 or LFY in axr2-1 mutants rescued the late flowering phenotype under SDs. Our results suggest that IAA7/AXR2 might act to inhibit the timing of floral transition under SDs, at least in part, by negatively regulating the expressions of the GA2Ooxl and GA2Oox2 genes.展开更多
The gibberellins(GAs)are phytohormones that play fundamental roles in almost every aspect of plant growth and development.Although GA biosynthetic and signaling pathways are well understood,the mechanisms that control...The gibberellins(GAs)are phytohormones that play fundamental roles in almost every aspect of plant growth and development.Although GA biosynthetic and signaling pathways are well understood,the mechanisms that control GA homeostasis remain largely unclear in plants.Here,we demonstrate that the homeobox transcription factor(TF)HB40 of the HD-Zip family regulates GA content at two additive con-trol levels in Arabidopsis thaliana.We show that HB40 expression is induced by GA and in turn reduces the levels of endogenous bioactive GAs by simultaneously reducing GA biosynthesis and increasing GA deac-tivation.Consistently,HB40 overexpression leads to typical GA-deficiency traits,such as small rosettes,reduced plant height,delayed flowering,and male sterility.By contrast,a loss-of-function hb40 mutation enhances GA-controlled growth.Genome-wide RNA sequencing combined with molecular-genetic ana-lyses revealed that HB40 directly activates the transcription of JUNGBRUNNEN1(JJUB1),a key TF that re-presses growth by suppressing GA biosynthesis and signaling.HB40 also activates genes encoding GA 2-oxidases(GA2oxs),which are major GA-catabolic enzymes.The effect of HB40 on plant growth is ultimately mediated through the induction of nuclear growth-repressing DELLA proteins.Collectively,our results reveal the important role of the HB40-JUB1 regulatory network in controlling GA homeostasis during plant growth.展开更多
基金supported by grants from the Ministry of Sciences and Technology of China (No. 2005CB120805 and 2006AA10A101)the National Natural Science Foundation of China (No. 30621001 and 30871512)
文摘Gibberellin （GA） 2-oxidase plays a key role in the GA catabolic pathway through 2β-hydroxylation.In the present study,we isolated a CaMV 35S-enhancer activation tagged mutant,H032.This mutant exhibited a dominant dwarf and GA-deficient phenotype,with a final stature that was less than half of its wild-type counterpart.The endogenous bioactive GAs are markedly decreased in the H032 mutant,and application of bioactive GAs （GA3 or GA4） can reverse the dwarf phenotype.The integrated T-DNA was detected 12.8 kb upstream of the OsGA2ox6 in the H032 genome by TAIL-PCR.An increased level of OsGA2ox6 mRNA was detected at a high level in the H032 mutant,which might be due to the enhancer role of the CaMV 35S promoter.RNAi and ectopic expression analysis of OsGA2ox6 indicated that the dwarf trait and the decreased levels of bioactive GAs in the H032 mutant were a result of the up-regulation of the OsGA2ox6 gene.BLASTP analysis revealed that OsGA2ox6 belongs to the class III of GA 2-oxidases,which is a novel type of GA2ox that uses C20-GAs （GA12 and/or GA53） as the substrates.Interestingly,we found that a GA biosynthesis inhibitor,paclobutrazol,positively regulated the OsGA2ox6 gene.Unlike the over-expression of OsGA2ox1,which led to a high rate of seed abortion,the H032 mutant retained normal flowering and seed production.These results indicate that OsGA2ox6 mainly affects plant stature,and the dominant dwarf trait of the H032 mutant can be used as an efficient dwarf resource in rice breeding.
基金supported by the National Natural Science Foundation of China (90917014 to H.-Q.Y.)the Ministry of Science and Technology of China (2006AA10A102)+2 种基金the National Special Grant for Transgenic Crops (2009ZX08009-081B to H.-Q.Y.)the Science and Technology Commission of Shanghai Municipality(10XD1402300 to H.-Q.Y.)the Shanghai Leading Academic Discipline Project(B209)
文摘Floral initiation is a major step in the life cycle of plants, which is influenced by photoperiod, temperature, and phytohormones, such as gibberellins （GAs）. It is known that GAs promote floral initiation under short-day light conditions （SDs） by regulating the floral meristem-identity gene LEAFY （LFY） and the flowering-time gene SUPPRESSOR OF OVEREXPRESSION OF CO 1 （SOC1）. We have defined the role of the auxin signaling component INDOLE-3-ACETIC ACID 7 （IAA7）/AUXIN RESISTANT 2 （AXR2） in the regulation of flowering time in Arabidopsis thaliana. We demonstrate that the gain-of-function mutant of IAA7/AXR2, axr2-1, flowers late under SDs. The exogenous application of GAs rescued the late flowering phenotype of axr2-1 plants. The expression of the GA20 oxidase （GA2Oox） genes, GA2Ooxl and GA2Oox2, was reduced in axr2-1 plants, and the levels of both LFY and SOC1 transcripts were reduced in axr2-1 mutants under SDs. Furthermore, the overexpression of SOC1 or LFY in axr2-1 mutants rescued the late flowering phenotype under SDs. Our results suggest that IAA7/AXR2 might act to inhibit the timing of floral transition under SDs, at least in part, by negatively regulating the expressions of the GA2Ooxl and GA2Oox2 genes.
基金supported by the European Rogional Dovelop-ment Fund Project Center for Experimental Plant Biology(no.CZ.02.1.01/0.00.0/16.0190000738)and the Czech Sc ence Foundation(no.18-10349S).
文摘The gibberellins(GAs)are phytohormones that play fundamental roles in almost every aspect of plant growth and development.Although GA biosynthetic and signaling pathways are well understood,the mechanisms that control GA homeostasis remain largely unclear in plants.Here,we demonstrate that the homeobox transcription factor(TF)HB40 of the HD-Zip family regulates GA content at two additive con-trol levels in Arabidopsis thaliana.We show that HB40 expression is induced by GA and in turn reduces the levels of endogenous bioactive GAs by simultaneously reducing GA biosynthesis and increasing GA deac-tivation.Consistently,HB40 overexpression leads to typical GA-deficiency traits,such as small rosettes,reduced plant height,delayed flowering,and male sterility.By contrast,a loss-of-function hb40 mutation enhances GA-controlled growth.Genome-wide RNA sequencing combined with molecular-genetic ana-lyses revealed that HB40 directly activates the transcription of JUNGBRUNNEN1(JJUB1),a key TF that re-presses growth by suppressing GA biosynthesis and signaling.HB40 also activates genes encoding GA 2-oxidases(GA2oxs),which are major GA-catabolic enzymes.The effect of HB40 on plant growth is ultimately mediated through the induction of nuclear growth-repressing DELLA proteins.Collectively,our results reveal the important role of the HB40-JUB1 regulatory network in controlling GA homeostasis during plant growth.
