Phytochrome B interacts with SWC6 and ARP6 to regulate H2A.Z deposition and photomorphogensis in Arabidopsis

Abstract

Light serves as a crucial environmental cue which modulates plant growth and development, and which is controlled by multiple photoreceptors including the primary red light photoreceptor, phytochrome B (phyB). The signaling mechanism of phyB involves direct interactions with a group of basic helix‐loop‐helix (bHLH) transcription factors, PHYTOCHROME‐INTERACTING FACTORS (PIFs), and the negative regulators of photomorphogenesis, COP1 and SPAs. H2A.Z is an evolutionarily conserved H2A variant which plays essential roles in transcriptional regulation. The replacement of H2A with H2A.Z is catalyzed by the SWR1 complex. Here, we show that the Pfr form of phyB physically interacts with the SWR1 complex subunits SWC6 and ARP6. phyB and ARP6 co‐regulate numerous genes in the same direction, some of which are associated with auxin biosynthesis and response including YUC9, which encodes a rate‐limiting enzyme in the tryptophan‐dependent auxin biosynthesis pathway. Moreover, phyB and HY5/HYH act to inhibit hypocotyl elongation partially through repression of auxin biosynthesis. Based on our findings and previous studies, we propose that phyB promotes H2A.Z deposition at YUC9 to inhibit its expression through direct phyB‐SWC6/ARP6 interactions, leading to repression of auxin biosynthesis, and thus inhibition of hypocotyl elongation in red light.

Phytochromes A and B Mediate Light Stabilization of BIN2 to Regulate Brassinosteroid Signaling and Photomorphogenesis in Arabidopsis

“…After the imbibed seeds were keep at 4°C for 3 days, they were grown on Murashige-Skoog (MS) nutrient medium plus 2% sucrose with 0.8% agar at 22°C under white light. The experiments involving red and far-red light illuminations were described previously ( Wei et al, 2021 ). Light spectra and intensity were measured with a Hand Held spectroradiometer (ASD) and a Li250 quantum photometer (Li-Cor) ( Wei et al, 2021 ).…”

“…The experiments involving red and far-red light illuminations were described previously ( Wei et al, 2021 ). Light spectra and intensity were measured with a Hand Held spectroradiometer (ASD) and a Li250 quantum photometer (Li-Cor) ( Wei et al, 2021 ).…”

“…Pull-down assays were performed as described previously with minor modifications ( Wang et al, 2018 ). pCold-TF-phyA-N (His-TF-phyA-N), pCold-TF-phyA-C (His-TF-phyA-C), pCold-TF-phyB-N (His-TF-phyB-N), and pCold-TF-phyB-C (His-TF-phyB-C) constructs were made previously ( Wei et al, 2021 ). The DNA fragment of BIN2 was cloned into pGEX-4T-1 (GE Healthcare Life Sciences, United States).…”

Arabidopsis cryptochrome 1 undergoes COP1 and LRBs‐dependent degradation in response to high blue light

“…ACT2 was used as an internal control for quantitative reverse transcription PCR (qRT‐PCR). qRT‐PCR analysis was described previously (Wei et al ., 2021). The primers used are listed in Supporting Information Table S1.…”

Signaling Mechanisms by Arabidopsis Cryptochromes

“…Interestingly, chromatin-remodeling mutants are also hyposensitive to red and far-red light, indicating that the SWR1 complex is also important for phytochrome signaling. Further studies have shown that phytochrome B interacts with SWC6 and ARP6 ( Mao et al, 2021 ; Wei et al, 2021 ).…”