Preliminary Study Of Arabidopsis RUS4 Action In Anther Development

Arabidopsis thaliana ROOT UV-B SENSITIVE4(RUS4)encodes a Domain of Unknown Function 647(DUF647)protein.Our laboratory has previously generated artificial micro RNA knockdown RUS4 Arabidopsis plants,referred to as amiR-RUS4.amiR-RUS4 plants have defects in anther dehiscence,pollen viability and filament elongation.It has been shown that Arabidopsis stamen development is controlled by auxin and jasmonates.In this study,we observed the number of flower buds and the morphology of roots in amiR-RUS4 plants and compared with that of the wild type.The results showed that RUS4 may be involved in the regulation of flowering anthesis,main root and root hair development in Arabidopsis.To investigate whether RUS4 knockdown affects auxin distribution and/or response,we used the auxin responsive DR5:GFP reporter.We crossed the DR5:GFP plants to amiR-RUS4 reporter and then analyzed the DR5 promoter activity in amiR-RUS4 background.Comparaed with the wild-type,the DR5:GFP signal in amiR-RUS4 anthers was much weaker,and the auxin distribution and responsive in amiR-RUS4 roots were also significantly reduced.q RT-PCR analysis showed that the expression of the flavonoids biosynthesis genes(TT4?TT5?TT6?FLS1?MYB11?MYB12?MYB111)in amiR-RUS4 plants was significantly up-regulated compared with that of the wild type.Tapetum development provides essential nutrients for anther development and pollen formation in Arabidopsis thaliana,we analysed the expression of CEP1 encoding cysteine protease involved in tapetum programmed cell death and transcription factor MYB103 regulating tapetum development.Our results showed that the expression levels of CEP1 and MYB103 decreased significantly in amiR-RUS4 stage 10 buds compared with that of the wild type,reflecting that abnormal execution of tapetum programmed cell death might be one of the causes for amiR-RUS4 male sterility.Taken together,these results suggest that RUS4 genes may negatively regulate the biosynthesis of flavonoids,and thus affect the anther development and pollen maturation in Arabidopsis;RUS4 genes may also affect the development of Arabidopsis roots by regulating the auxin pathway.