Phytochrome B Stabilizes The Knox Transcription Factor Bpknat1 To Promote Lightinitiated Seed Germination In Arabidopsis Thaliana Dachuan Gu Yahan Wang Minglei Zhao Hangcong Chen Suhua Wu Xia Jin Ling Deng Rujun Ji Jinyan Xu Feng Zheng Xuncheng Liu by Dachuan Gu & Yahan Wang & Minglei Zhao & Hangcong Chen & Suhua Wu & Xia Jin & Ling Deng & Rujun Ji & Jinyan Xu & Feng Zheng & Xuncheng Liu instant download after payment.

Abstract: Seed germination is a critical step in the life cycle of plants. The far-red/red 31 light photoreceptor phytochrome B (phyB) plays a dominant role in promoting seed 32 germination, mainly by modulating the metabolism of gibberellin (GA) and abscisic 33 acid (ABA), although the underlying mechanism remains poorly understood. In this 34 study, we identified BREVIPEDICELLUS (BP)/KNAT1, a KNOX transcription 35 factor that acted downstream of phyB and activated light-initiated seed germination in 36 Arabidopsis thaliana. BP underwent ubiquitination modification and was degraded 37 through the 26S proteasome pathway. PhyB directly interacted with BP in vitro and in 38 vivo and stabilized BP protein by decreasing its ubiquitination in imbibed seeds. A 39 genome-wide transcriptomic analysis revealed that BP and phyB co-regulated the 40 expression of genes related to ABA biosynthesis and signaling transduction, seed 41 dormancy, and cell wall organization. BP repressed the expression of two key ABA 42 biosynthetic genes, NCED6 and NCED9, and decreased ABA levels in imbibed seeds43 under phyB-activated conditions. BP directly bound to NCED6 and NCED9 and44 repressed their expression by increasing the levels of H3K27me3, a repressive histone 45 modification marker. Genetic analysis revealed that NCED6/NCED9 acted epistasis of46 BP in phyB-dependent seed germination. Taken together, this study reveals a 47 transcriptional module consisting of phyB-BP-NCED6/9, which transfers light signals48 that inhibit ABA biosynthesis, thereby promoting light-induced seed germination.