Cloning And Functional Analysis Of Br Regulating Gene BBRG9 From Moso Bamboo

Bamboo is one of the most important non-timber forest plants in the world,which has considerable economic,ecological and cultural value.The growth and development of bamboo were reported to be coordinated by multiple endogenous plant hormones.Brassinosteroids(BRs)are a group of steroid hormones in plants,which has various physiological functions.In order to explore how brassinosteroid regulates the growth and development of moso bamboo,we focused on a BR responsive gene,Bamboo BR responsive 9(BBRG9).(1)Bioinformatics analysis showed that the homologous genes of BBRG9 were only found in the poaceae family plant.Most close homologs were identified from Anastatica,Brachypodium and rice.No function analysis was reported about BBRG9 family proteins.(2)BBRG9 gene was firstly identified as BR down-regulated gene from our previous RNA-seq experiment.BBRG9 expression is increased by BR biosynthesis inhibitor propiconazole(PPZ)and decreased by BR treatment in the root.However,the BR and PPZ effects on BBRG9 were not obvious in the shoot part.(3)BBRG9 was fused with YFP tag and transiently transformed to epidermis cells of tobacco leave,and was found to be located in chloroplast,nucleus and membrane.(4)To further investigate its biological function,BBRG9 overexpression vector was transformed to Arabidopsis.Multiple transgenic lines showed dwarf phenotype,narrow and curved rosette leaves with yellowish margin.In addition,the lateral branches from basal nodes were increased in the BBRG9 overexpressing lines,an apical dominance loss phenotype.BBRG9 may plays an important role in the stem elongation,leaf development and lateral branching control processes.Taken together,we identified and cloned a novel BR responsive gene,BBRG9,from moso bamboo.Expression level of BBRG9 is specifically repressed by BR in thebamboo root.Our results suggested that BBRG9 works as a growth repressor when overexpressing in Arabidopsis.Our work provided a theoretical basis for further of study moso bamboo and provide a new sight for the development of forestry economy.