636 / 2019-04-28 11:13:57

The regulation of sporopollenin synthesis genes for rapid pollen wall formation in Arabidopsis

sporopollenin synthesis,pollen wall,transcriptional regulation,protein interaction

Growth and Development > Growth and Development

The outer pollen wall (Sexine) is rapidly formed to protect pollen formation. Sporopollenin is the major component of sexine, and its synthesis involves about eight genes in Arabidopsis. MS188 and its direct upstream regulator AMS are two transcription factors essential for tapetum development. Here, we show all the sporopollenin synthesis proteins were specifically expressed in tapetum and secreted into anther locules. MS188, a MYB transcription factor in tapetum, directly regulates the expression of PKSA, PKSB, MS2 and CYP703A2. In contrast, the expression of CYP704B1, ACOS5, TKPR1 and TKPR2 is significantly reduced in ams but not affected in ms188. However, MS188 but not AMS can activate their expression. In ms188, dominant suppression of MS188 homologues reduced the expression of these genes, suggesting that MS188 and other MYB family members played a redundant role to activate their expression. In ams, the mutant of MS188 upstream regulator, the expression of MS188 rescued most sporopollenin synthesis gene expression. Therefore, MS188 is a key regulator for activation of sporopollenin synthesis. AMS and MS188 may form a feed-forward loop to facilitate the expression of the sporopollenin synthesis pathway for rapid pollen wall formation.