The MtN3Family Genes Affect Microspore Primexine Development In Arabidopsis Thaliana

The pollen wall plays important roles during plant reproductivedevelopment and provides strength to avoid physical pressure andattack from the environment. Sugar is essential for the production ofplant nectar, seed and pollen exine development. Previous reportshowed that Arabidopsis RPG1protein function as sugar transporterand is required for exine development and the male sterile of the earlyinflorescence.Here, we performed more detailed Transmission ElectronicMicroscopy (TEM) observation of the tetrad development in rpg1. Ourresults showed that the rpg1muatnt primexine matrix was less and themicrospore membrane didn’t form undulation structure which resultingin the abnormal accumulation of sporopollenin to microsporemembrane and the later defective exine pattern. Callose staining andreal-time PCR analysis showed that both the callose deposition aroundthe tetrad and the expression of CALS5were reduced in rpg1. Toinvestigate the mechanism of the recovery of fertility of later stageinflorescence in rpg1, another mutant of MtN3/saliva family rpg2wascharacterized according to the predicted expression and sequencealignment. Mutation of RPG2did not affect plant fertility but causedslight defect of reticulate exine under SEM observation. In situhybridization and promoter fused with GUS reporter revealed that RPG2is expressed in mature anther. Transient transformation of tobacco leafwith RPG2fused to Subcellular localization demonstrated that RPG2was a membrane targeted protein. Double mutant rpg1rpg2enhancethe defective pollen exine structure and the male sterile phenotype ofrpg1indicating RPG2may also functions in supporting male fertility inArabidopsis. Together all, our finding further elucidate the detail aboutthe process of pollen exine formation and provide the understanding of sugar transporting in help primexine matrix deposition and callsoebiosynthesis. Moreover, our study explains the mechanism of the restoreof fertility of male sterile mutant in later development stage.