The Brassinosteroid’s Effect On The Secondary Growth Of Eucalyptus Grandis And Preliminary Function Analysis Of The Related Genes

Brassinosteroid(BR) is a kind of sterols plant endogenous hormones, which widely exist in different organs. It can promote plant growth, increase crop yield, resist disease s etc.,. In this study, BR applied to rooting medium of Eucalyptus grandis. Results sho wed that concentration of below 0.05 mg.L-1 BR could improve the rooting rate, while high concentration of BR inhibited rooting slice analysis showed: 0.10 mg.L-1 BR cause d huge increase in cambium cells in stem base, and also in lignification degree increas ed. When BR concentration reached 20 ng.m L-1 could promote the growth of stem cellulo se in half year E. grandis, inhibit below this concentration. Meanwhile, the number of lignification cells increased significantly, the degree accumulated of wood fiber reduced in stem through BR processed in half year born E. Grandis.In order to further research on the role of BR in secondary vascular development of E. grandis, this study chose BRASSINOSTEROID1(BR1I) and INSENSITIVE BRASSIN AZOLE RESISTANT(BZR) family. Four BRI1 genes and four BZR genes on E. grandis were cloned successfully using RT-PCR respectively. Bioinformatics analysis using Prot Param、SWISS-MODEL and other molecular biology online server revealed characteristi cs of BRI1 and BZR. Results showed that BRI1 family have stabilitale property, signal peptide and complex space structure. Three motifys were found in BRI1 protein family.Specially, BRI1 extracellular domain contains 24 repeat sequences which have rich leu cine(LRR). "Island" area(ID) on the membrane outside which between 20 and 21 LR R accept signal stimuli. BZR prtein family is not stable and single spatial structure. Th ere was a domain(DUF822) structure in all BZR family where combines DNA easily.EgrBZR2 express in xylem distinctively through tissue expression analysis Furthermore,pENTER-clone vector and over-expression vector of EgrBRI1 and EgrBZR were success fully constructed which would lay the foundation for molecular regulation mechanism o f E. grandis wood formation.