油菜素内酯基因助力杨树遗传改良

 

     杨树是世界上广泛栽培的重要树种之一，具有速生丰产、实用性强等特点，在城市绿化、生态建设和木材生产中发挥着不可替代的巨大作用。杨树基因组小，易于遗传操作、同时又是根癌农杆菌的天然寄主，便于遗传转化，因此杨树被认为是林木基因工程研究的模式植物。

      油菜素内酯（Brassinosteroids，BRs）作为第六激素，属新型广谱植物生长调节剂，在植物生长发育，生物和非生物胁迫响应中扮演重要角色。在拟南芥中，AtCYP85A2编码的细胞色素P450单加氧酶催化甾酮为油菜素内酯，是油菜素内酯合成途径的限速酶。
      来自鲁东大学的特聘教授张红霞团队，将AtCYP85A2的同源基因PtCYP85A3构建到35S启动子的表达盒中，进行遗传转化获得PtCYP85A3基因超表达的转基因番茄和杨树，转基因植物体内的BR含量和生物量均显著增加。与非转基因对照相比，转PtCYP85A3基因番茄的株高、植株鲜重和果实产量分别增加了50%,56%和43%，类似地，转基因杨树的株高和主茎的直径分别增加了15%和25%。进一步研究发现，超表达PtCYP85A3基因可以促进木质部的形成，而对纤维素和木质素的组成以及细胞壁的厚度没有影响。该研究表明，PtCYP85A3基因可望应用于快速生长树木的基因工程改良，进而增加木材产量。
Plant biotechnology Journal, 17 June 2017
Overexpressionof Populus trichocarpa CYP85A3 promotes growth and biomass productionin transgenic trees
Authors
Yan-Li Jin, Jie Tang, Hai-Hai Wang,Chun-Mei Jiang, Yan Bao, Yang Yang, Mei-Xia Liang, Zhen-Cang Sun, Fan-JingKong, Bei Li, Hong-Xia Zhang
Summary
Brassinosteroids(BRs) are essential hormones that play crucial roles in plant growth, reproduction and response to abiotic and biotic stress. In Arabidopsis, AtCYP85A2 works as a bifunctional cytochrome P450 monooxygenase to catalyse theconversion of castasterone to brassinolide, a final rate-limiting step in the BR-biosynthetic pathway. Here, we report the functional characterizations of  PtCYP85A3, one of the three AtCYP85A2 homologous genes from Populus trichocarpa. PtCYP85A3 shares the highest similarity with AtCYP85A2 and can rescue the retarded-growth phenotype of the Arabidopsis cyp85a2-2 and tomato dx mutants. Constitutive expression of PtCYP85A3, driven by the cauliflower mosaic virus 35S promoter, increased the endogenous BR levels and significantly promoted the growth and biomass production in both transgenic tomato and poplar. Compared to the wild type, plant height, shoot fresh weight and fruit yield increased 50%, 56% and 43%, respectively, in transgenic tomato plants.Similarly, plant height and stem diameter increased 15% and 25%, respectively,in transgenic poplar plants. Further study revealed that overexpression of PtCYP85A3 enhanced xylem formation without affecting the composition of cellulose and lignin, as well as the cell wall thickness in transgenic poplar.Our finding suggests that PtCYP85A3 could be used as a potential candidate genefor engineering fast-growing trees with improved wood production.