KNOXI/ARP调控单元在豆科模式植物蒺藜苜蓿复叶发育中的功能研究

KNOXI genes play the important roles in leaf development. The expression patterns of KNOXI genes regulated by ARP gene are different in simple leaf and compound leaf, resulting in the diversity of leaf form. However, except for Arabidopsis thaliana and its relative Cardamine hirsuta, the function of KNOXI/ARP module is largely unknown in other species due to the lack of relevant mutants. As the model legume species, Medicato truncatula has the simplest compound leaf form, which is recognized as the new model species for compound leaf study. To identify mutants with defects in compound leaf development, ~13,000 independent lines of Tnt1 retrotransposon-tagged M. truncatula populations were screened. One mutant line with obvious changes in leaf development was isolated. Then we identified that the mutation in M. truncatula ARP gene MtPHAN caused the mutant phenotype. To further study the functional relationship between MtPHAN gene and MtKNOXI gene family, we isolated the mutants of MtKNOX1, MtKNOX2 and MtKNOX6 using reverse screening in ~19,000 mutant lines. This project is proposed to study the interaction between MtKNOXI genes and MtPHAN gene in the compound leaf development in M. truncatula. In addition, the roles of auxin and other leaf development regulation pathways/genes will be investigated in the mtknoxi and mtphan mutant background. This project is the first functional study of the MtKNOXI/ MtPHAN module in legume species, which will provide the insights for the quality improvement of important forage alfalfa.

KNOXI基因家族在叶发育中扮演着重要角色。KNOXI在复叶植物和单叶植物中的表达差异导致了叶片形态的多样性，其表达模式受到APR基因的调控。蒺藜苜蓿是豆科模式植物，也是复叶研究的新模式植物。为了研究其复叶发育机制，我们通过正向遗传学筛选了约13，000个突变体株系并分离出蒺藜苜蓿ARP 基因 MtPHAN的突变体，同时通过反向遗传学筛选了约19，000个突变体株系并分离出MtKNOX1, MtKNOX2 和MtKNOX6基因的突变体。在本项目中，我们拟对MtPHAN与MtKNOXI基因家族之间的互做进行分析，同时拟对生长素和其他叶发育调控基因与MtPHAN/MtKNOXI调控单元之间的互做开展系统研究。这一项目首次阐明了MtPHAN/MtKNOXI调控单元在豆科植物中的作用机制，相关研究结果将对重要牧草紫花苜蓿的品质改良提供新的研究思路。

KNOXI基因家族成员在顶端分生组织维持和叶片发育方面起到重要作用。KNOXI基因的表达模式受APR基因的精细调控。在豆科IRLC分支的物种中，KNOXI调控复叶发育的功能被LEAFY的同源基因所取代。蒺藜苜蓿是豆科模式植物，属于IRLC分支，其复叶发育调控机理很大程度上是未知的。为了研究蒺藜苜蓿复叶的发育机制，我们利用正向遗传学筛选分离出蒺藜苜蓿ARP基因MtPHAN的突变体，同时通过反向遗传学筛选分离出MtKNOX1，MtKNOX2和MtKNOX6基因的突变体。本研究通过分子生物学和遗传学等方法系统分析了ARP基因MtPHAN与STM/BP-Like KNOXI及SGL1基因之间的关系。首次发现：STM/BP-Like KNOXI与ARP基因调控单元之间的拮抗关系不存在；STM/BP-Like KNOXI基因的表达水平与叶片的复杂性正相关；生长素极性运输的扰乱不能改变STM/BP-Like KNOXI基因的表达；STM/BP-Like KNOXI和SGL1基因以平行的通路调控复叶发育。上述结果证实KNOXI/ARP调控单元参与豆科模式植物蒺藜苜蓿的复叶发育，对该发育进程的理解有助于深入阐明复叶模式复杂的调控网络。