Phytochromes are red (R) and far-red (FR) light photoreceptors in plants, and PHYTOCHROME-INTERACTING FACTORS (PIFs) are a group of basic helix-loop-helix family transcription factors that play central roles in repressing photomorphogenesis. Here, we report that MYB30, an R2R3-MYB family transcription factor, acts as a negative regulator of photomorphogenesis in Arabidopsis (Arabidopsis thaliana). We show that MYB30 preferentially interacts with the Pfr (active) forms of the phytochrome A (phyA) and phytochrome B (phyB) holoproteins and that MYB30 levels are induced by phyA and phyB in the light. It was previously shown that phytochromes induce rapid phosphorylation and degradation of PIFs upon R light exposure. Our current data indicate that MYB30 promotes PIF4 and PIF5 protein reaccumulation under prolonged R light irradiation by directly binding to their promoters to induce their expression and by inhibiting the interaction of PIF4 and PIF5 with the Pfr form of phyB. In addition, our data indicate that MYB30 interacts with PIFs and that they act additively to repress photomorphogenesis. In summary, our study demonstrates that MYB30 negatively regulates Arabidopsis photomorphogenic development by acting to promote PIF4 and PIF5 protein accumulation under prolonged R light irradiation, thus providing new insights into the complicated but delicate control of PIFs in the responses of plants to their dynamic light environment.

植物色素是植物中的红色（R）和远红色（FR）光感受器，而植物染色体相互作用因子（PIF）是一组基本的螺旋-环-螺旋家族转录因子，在抑制光形态发生中起关键作用。在这里，我们报告MYB30，R2R3-MYB家庭转录因子，充当拟南芥（Arabidopsis thaliana）光形态发生的负调控因子）。我们显示，MYB30优先与植物色素A（phyA）和植物色素B（phyB）全息蛋白的Pfr（活性）形式相互作用，MYB30水平是由phyA和phyB在光照下诱导的。先前已证明，在R射线照射下，植物色素可引起PIF的快速磷酸化和降解。我们目前的数据表明，MYB30通过直接与启动子结合以诱导其表达并抑制PIF4和PIF5与phyB的Pfr相互作用，从而在延长的R光照射下促进PIF4和PIF5蛋白的重新积累。此外，我们的数据表明，MYB30与PIF相互作用，并且它们可加在一起起到抑制光形态发生的作用。综上所述，