Functional Study Of AtHSPR On GA-mediated Flowering Development In Arabidopsis

Gibberellin is an important plant hormone and plays an important role in seed germination,root length,leave growth,floral induction,seed and fruit development.The development of flower and silique is very important in Arabidopsis.There are four pathways synergistically regulate Arabidopsis flowering,autonomous pathway,vernalization pathway,light-dependent pathway and gibberellin pathway,respectively.Meanwhile,gibberellin plays an important role in silique development in Arabidopsis.A mutant,under the C24 background,named athspr(Arabidopsis thaliana heat shock protein trlated)was screened by T-DNA insertion in our lab.Results showed that athspr mutant was delayed in flowering time compared with WT and At HSPR overexpression line under long-day condition.And this difference became significant under short-day condition.In addition,the percentage of fertility silique in athspr mutant was also decreased.To reveal the function of At HSPR in flowering and silique development in Arabidopsis,the function of At HSPR on flower and silique development in Arabidopsis was studied by phenotype comparison,promoter analysis,exogenous GA₃ treatment and q RT-PCR etc.,and the main results are as follows:1.There are several cis-elements in At HSPR promoter,which response to gibberelin and light signaling,using a software named Plant CARE.And the activity of At HSPR promoter was up-regulated in pro At HSPR::GUS line after treated with exogenous GA₃.2.Flowering time,plant height,number of rosette leaves were counted in pro At HSPR::At HSPR transformed line,WT and athspr mutant under long-day condition.We found that pro At HSPR::At HSPR transformed line was ealier on flowering time than WT line,while athspr mutant was delayed compared with WT.And earlier flowering companied with higher plant and less rosette numbers.It suggest that At HSPR plays an important role in flowering time in Arabidopsis.3.Exogenous GA3 partially recovered the phonotype of athspr mutant under long-day condition(16h light/8h dark).The flowering time of GA-treated mutant was earlier,plant height higher and rosette numbers was much less compared to original mutant.The expression of FT and SOC1genes were decreased in athspr mutant compared with pro At HSPR::At HSPR transformed line and WT.So At HSPR may regulate flowering development through regulating the expression level of FT and SOC1 genes.4.Under short-day condition,the differences of flowering time was significant between WT and athspr mutant.And athspr flowering time became earlier after exogenous GA₃ treatment.Exogenous GA₃ could complement the function of At HSPR in athspr mutant under short-day condition in Arabidopsis.Reasults of q RT-PCR showed that the expression levels of LFY and SOC1 was decreased in the mutant,and the expression levels of GA20ox1,GA20ox2,GA3ox1 also went down but GID had no significant difference between athspr mutant and WT.So At HSPR plays an important role in GA-mediated flowering development in Arabidopsis.5.Analysis of different types of siliques in Arabidopsis showed that the number of infertile siliques became rare and had no difference in both WT line and At HSPR overexpression line under SD and LD conditions.But the percentage of infertile silique in athspr mutant was increased under SD condition.It showed that At HSPR plays an important role in sillique development.Exogenous GA₃ can rescue the silique infertility in athspr mutant.Under SD condition,GA could improve the percentage of silique fertility in athspr mutant.So At HSPR take part in GA-mediated silique development in Arabidopsis.Above all,athspr mutant was delayed on flowering time with lower plant height and less rosstte numbers compared with WT line.At the same time,the percentage of fertile silique became lower under short-day condition.And exogenous GA₃ could confer an earlier flowering time and higher number of fertility siliques to athspr mutant.q RT-PCR results showed that the expression levels of some GA-biosynthesis genes(GA20ox1,GA20ox2 and GA3ox1)and some flowering genes(SOC1 and LEY)was decreased in the mutant.In conclusion,At HSPR take part in GA-mediated flowering and silique development in Arabidopsis.