Screening For Transgenic Plants Overexpressing Arabidopsis LRR-RLKs And Functional Analyses Of TRR1and TRR2

Receptor-like protein kinases (RLKs) are a group of specific protein kinases, which play important roles in plant growth and development. Leucine-rich repeat (LRR)-RLK is the largest family of the RLK superfamily in Arabidopsis containing223members. There are three domains in a typical LRR-RLK:an extracellular domain, an intracellular domain and a single-pass transmembrane domain. Functions of a handful of LRR-RLKs have been defined, such as BR11, BAK1, FLS2, EFR, SERKs, and EMS1. To reveal the functions of other LRR-RLKs, transgenic plants overexpressing these genes were created and screened in wildtype Arabidopsis. Western blot analysis was employed to confirm the expression of transgenes in transgenic plants. Transgenic plants were identified for a total of102LRR-RLKs for phenotypic analyses.Overexpression of TRR1(Tapetum Related RLK1) and TRR2displayed short and narrow leaves in their transgenic plants. Loss-of-function analyses indicated that TRR1and TRR2play important roles in anther development, controlling degradation of tapetum and microsporogenesis. Double null mutant trrl trr2shows enlarged tapetum and a few microsporocytes can develop to produce fertile microspore and mature pollen. More severe phenotypes were also observed that the microsporocytes could not develop to produce pollen, and the anther finally collapsed. These two phenotypes can exit within one anther, resulting in sterile microsporocytes in one collapsed pollen sac, and enlarged tapetum in another pollen sac. The defective microsporocytes and tapetum can be observed at stage6and stage9of anther development, respectively. RT-PCR analyses indicated that the expression levels of tapetum related genes DYT1, SPL and MS2were all upregulated in trrl trr2mutant. Our data suggested that TRR1and TRR2could be involved in the anther development signaling network mediated by SERKs, SPL, DYT1and MS2.