杨树油菜素内酯合成基因PtCYP85A5在杨树生长发育和耐逆境胁迫中的功能研究及其应用

油菜素甾醇类化合物（BRs）是一类新型激素，在植物的种子萌发、光合作用、维管分化、育性以及逆境反应等方面起重要作用。油菜素甾酮（CS）是合成油菜素内酯（BL）的重要前体，具有和BL相似的生理功能。Dwarf是番茄中合成CS的基因，杨树中PtCYP85A5的氨基酸序列同Dwarf的相似性最高。首先我们用PtCYP85A5的过表达载体互补拟南芥和番茄的CYP85A突变体，同时转化它们的野生型来确定该基因的生物学功能。然后将PtCYP85A5的正义、反义载体导入山新杨中，研究转基因杨树的表型、木质部结构、细胞壁组分以及转录本的变化来揭示该基因在杨树生长发育中的功能和作用机理。此外，对转基因杨树进行逆境处理，分析转基因杨树的表型、相关生理指标和转录本变化来揭示BRs在杨树抗逆中的作用及机理。以此获得生物量及耐逆性显著提高的转基因新材料，为通过改变内源BRs的合成对木本植物进行遗传改良提供理论基础

Brassinosteroids (BRs) play essential roles in plant development, including germination, photomorphogenesis, vascular tissue differentiation,development of reproductive organs, and protecting plants from various biotic and abiotic stresses. Castasterone (CS), considered to be a direct biosynthetic precursor of the most biologically active brassinosteroid (BL), displays the same physiological responses as that induced by BL. Formation of castasterone in tomato is catalyzed by Dwarf. In poplar, PtCYP85A5 is the closest homology to the Dwarf. In this work, we will perform the functional analyses of PtCYP85A5 in poplar development and abiotic stress tolerance. We firstly determine the biological function of PtCYP85A5 by over-expressing PtCYP85A5 in the lost-of-function mutants of brassinosteroid biosynthesis and wild types of Arabidopsis and tomato. Then, over-expression vector and antisense vector of PtCYP85A5 will be transformed into poplar to examine its biological functions in poplar development,especially in wood formation, by studying the changes in phenotype, wood structure, cell wall components and expression of transcripts of the transgenic plants. In addition, transgenic poplar over-expressing or down-expressing PtCYP85A5 will be treated with different abiotic stresses. Then the phenotype, physiological changes and stress-related genes will be analyzed to determine the function of BRs in poplar abiotic stresses tolerance. We believe that new transgenic poplar lines with significantly improved plant biomass or tolerance to abiotic srtesses would be acquired. This work will also provide theoretical information for genetic improvement of woody plants by controlling the content of endogenous BRs using transgenic technology.