Functional analysis of a MYB transcription factor BrTDF1 in the tapetum development of Wucai (Brassica rapa ssp.)

摘要

Ogura cytoplasmic male sterility (ogu-CMS) has been widely used by breeders for vegetables in the genus Brassica; however, the molecular mechanism of this male sterility remains unclear. The tapetum plays a crucial role in anther development by providing nutrients and secreting callose for pollen development. In this study, we found that the tapetum was abnormally vacuolated after meiosis in Wucai ogu-CMS, which led to the abortion of microspores. The TDF1 gene is essential for early tapetal development. Combined with the characteristics of abortion in ogu-CMS, qRT-PCR analysis showed that the BrTDF1 gene was expressed in all detected tissues from fertile plants, and the transcript levels of this gene in fertile buds were far higher than those in vegetative organs. Compared with the fertile line, BrTDF1 exhibited lower expression in all developmental stages of buds from the sterile line. In addition, the examinations of A6 and EXPBS genes suggested that the expressions of these genes in ogu-CMS were lower than those in its maintainer line. Further analysis of its function showed that constitutive expression of BrTDF1 in the Arabidopsis tdfl mutant transgenic lines could restore its fertility. These results indicated that this MYB transcription factor BrTDF1 is required for tapetal development in Wucai.