Functional Study Of BR On Plant Shoot Branching

Shoot branching profoundly affects plant architecture and is closely related to plants' yield and adaptability to environment.Shoot branching is produced from shoot apical meristem and is regulated by the interplay of diverse hormonal and environmental signals.Brassinosteroids(BRs)are growth-promoting steroid hormones,which are involved in regulating a series of plant development processes and physiological responses.However,their roles in shoot branching are rarely reported.To solve this question,firstly,the number of branches in BR-related mutants was systematically analyzed.The results showed that the number of branches increased significantly in the mutants in which BR biosynthesis was increased and signal was enhanced.On the contrary,the number of branches was significantly decreased in BR-deficient mutants and BR-insensitive mutants.Secondly,transcriptional analysis showed that the expression of RAX1,a MYB transcription factor,which plays an important role in AM initiation,was up-regulated by BR.So we speculated that BR may regulate the AM initiation through RAX1.At present,relevant genetics materials are under preparation.Besides,we screened a BR-regulated transcription factor,BRT3,which interacted with RAX1 through Y2H.The statistics showed that the number of lateral branches of BRT3 over expression lines was significantly increased compared with the wild-type.Similarly,through GUS staining,we found BRT3 was specifically expressed in the axillary.But for the loss-of-function mutants of BRT3,there was no difference between them and the wild-type in the number of lateral branches.We supposed that the two genes were redundant to the other members of NAC family.Besides,BRT3 was also specifically expressed in the abscission zone and valve margins of silique,which suggested that BRT3 played a role in the organ abscission and dehiscence in Arabidopsis.In addition,our researches have shown that the BRT3 was involved in plant adversity stress responses.The results of the experiments were as follows:firstly,we found that BRT3 overexpression lines enhanced the resistance to the drought in comparison with the wild-type.Further study suggested BRT3 offered drought tolerance may via lowering transpiration rate.Secondly,BRT3 overexpression lines were more sensitive than control plants to ABA during seed germination and root growth,indicating that BRT3 may be involved in ABA signaling pathways.