The Function Of RUS4 In Stamen Maturation In Arabidopsis Thaliana

Arabidopsis ROOT UV-B SENSITIVE4(RUS4)encodes a DUF647-containing protein,whose function is poorly understood.We previously reported Arabidopsis artificial micro RNA(ami RNA)knocking down RUS4 plants,referred to as ami R-RUS4,have severely reduced male fertility with a defect in anther dehiscence.However,ami R-RUS4 plants have additional phenotypes that we investigate in this study.Here,we show that ami R-RUS4 plants also exhibits defects in filament elongation.As the translational RUS4-GFP fusion protein has been localized to the chloroplasts where the first step of jasmonate(JA)biosynthesis take place,leading to the hypothesis that RUS4 may be involved in JAmediated stamen development.Consistent with this idea,the expression of several JA biosynthetic genes is markedly increased in flower buds of the ami R-RUS4 plants compared to that of the wild-type.Importantly,the transcript abundance of MYB-type transcription factor MYB21,MYB24,MYB57,and MYB108,which have been shown to regulate JAmediated stamen maturation,is significantly reduced in stamens of ami R-RUS4 plants relative to the wild-type.Taken together,these results suggest that RUS4 may function in the process of pollen maturation,in concert with anther dehiscence and filament elongation,by affecting the expression of the JA biosynthetic and signaling genes.There is an increasing body of evidence that auxin acts through jasmonate to control stamen development.Real-time quantitative RT-PCR analysis of the expression of auxin repressor gene IAA19 and auxin response factors genes ARF8.2 and ARF8.4 showed that these genes are altered in ami R-RUS4 flower buds.Therefore,we speculate that RUS4 might play a role in auxin signal transduction pathway,thereby modulating Arabidopsis stamen development.