拟南芥三个不同的生长素糖基转移酶基因的功能关系研究

Auxin is one type of plant homones that plays important roles in many aspects of plant growth and development. The glucosylation of auxins is found to widely occur in plants. And glycosylation is considered as an important regulatory mechanism for the homeostasis of auxins. In our past research, UGT74D1 was identified to be an auxin glycosyltransferase from Arabidopsis. A phenotypic analysis for the UGT74D1 overexpressing transgenic plants was carried out, and UGT74D1 overexpression lines displayed a number of changes that resembled those described previously in lines in which auxin levels were depleted. However, the ugt74d1 mutant had the similar phenotypes with wild-type. Meanwhile, two other auxin glycosyltransferases UGT84B1 and UGT74E2 had been identified from Arabidopsis. But there are some phenotypic differences between UGT74D1 and the other two auxin glycosyltransferases overexpression lines. These findings suggest that their in planta function might have diverged during plant growth and development. Therefore, this proposal will be observed through molecular genetic techniques such as gene knock-out manipulation of the three genes, and then we can change the glucosylation level of auxins. Further, we will investigate the effects of glucosylation on the auxin homeostasis, the auxin metabolism, the auxin signal transduction, the expression pattern and the plant growth and development. Through this research, we will get new insight into the molecular mechanism how auxin glycosyltransferases maintain auxins homeostasis and normal growth and development of plants.

生长素是一类非常重要的植物激素，参与调控植物生长发育的诸多过程。生长素的糖基化修饰现象在植物界中普遍存在，并影响植物体内生长素含量的动态平衡。申请人从拟南芥克隆到一个能够糖基化生长素的糖基转移酶UGT74D1基因，发现UGT74D1过表达体表现出一些生长素缺陷性表型，但是它的突变体并没有表现出相反的生长素累积表型。与另外两个已鉴定的生长素糖基转移酶UGT84B1和UGT74E2相比，它们过表达株系的表型并不完全一致，推断它们在植物生长发育的过程中可能各有分工。因此本项目拟利用分子遗传学方法，从这三个生长素糖基转移酶的系列功能缺失体入手，研究它们在调节生长素平衡、代谢修饰、信号传导、表达模式以及控制生长发育表型上的功能关系，探讨生长素糖基化修饰基因调节植物生长素动态平衡及生长发育的分子机制。

生长素是一类非常重要的植物激素，参与调控植物生长发育的诸多过程。生长素的糖基化修饰现象在植物界中普遍存在，并影响植物体内生长素含量的动态平衡。本项目中，申请人研究了生长素糖基转移酶UGT74D1在植物体内的表达特异性，及其控制叶柄夹角的生理功能和分子机制，证明UGT74D1在调控拟南芥叶柄夹角的大小中具有潜在作用。其次,从拟南芥克隆到一个新的生长素糖基转移酶UGT84A2基因，并对其生理作用进行探究，发现UGT84A2过表达株系通过增加IBA的含量，抑制ARF6，ARF8和开花途径下游基因的转录来延迟植物的开花时间。但是已鉴定出的生长素糖基转移酶过表达株系的表型并不完全一致，它们的突变体并没有表现出相反的生长素累积表型，推断它们在植物生长发育的过程中可能各有分工。所以随后利用分子遗传学方法，构建了三个代表性的生长素糖基转移酶的系列功能缺失体，将研究它们在调节生长素平衡、代谢修饰、信号传导、表达模式以及控制生长发育表型上的功能关系。为生长素糖基化修饰基因调节植物生长素动态平衡及生长发育提供理论依据。