Coordinated regulation of pre-mRNA splicing by the SFPS-RRC1 complex to promote photomorphogenesis ($) (Plant Cell)

Phytochromes are a family of red/far-red light photoreceptors, which positively regulate photomorphogenesis upon red-light perception. Photomorphogenesis is driven by light-induced global transcriptional reprogramming, of which phytochromes are one of the most important regulators. In addition to transcriptional regulation, recent experimental evidence suggests that phytochromes also regulate pre-mRNA splicing of a large number of genes, and at least one of the splicing factors, SFPS (Splicing Factor for Phytochrome Signaling), is shown to interact with phytochromes and coordinately modulate pre-mRNA splicing. In this paper, Xin et al. have identified one more splicing factor RRC1 (Reduced Red-light responses in cry1cry2 background 1) as one of the interacting proteins of SFPS and phyB. Through RNA- seq analysis authors showed that RRC1 regulates the expression and pre-mRNA splicing of a large number of genes, both under dark and red- light treatment. Moreover, they also found that RRC1 and SFPS together co-regulate hundreds of splicing events, suggesting they might function, in part, in the same complex and pathway. Finally, they conclude that phytochromes modulate the pre-mRNA splicing by directly interacting with splicing factors and (probably) regulating their activity in response to red-light irradiation. Overall, this paper provides a comprehensive view of yet another novel molecular mechanism of phytochrome- mediated signaling to promote photomorphogenesis in Arabidopsis. (Summary by Ruijiao Xin) Plant Cell: 10.1105/tpc.18.00786