title: Rice Phytochrome B (OsPhyB) Negatively Regulates Dark- and Starvation-Induced Leaf Senescence.
abstract: Light regulates leaf senescence and light deprivation causes large-scale transcriptional reprogramming to dismantle cellular components and remobilize nutrients to sink organs, such as seeds and storage tissue. We recently reported that in Arabidopsis (Arabidopsis thaliana), Phytochrome-Interacting Factor4 (PIF4) and PIF5 promote dark-induced senescence and natural senescence by directly activating the expression of typical senescence-associated genes (SAGs), including ORESARA1 (ORE1) and ETHYLENE INSENSITIVE3 (EIN3). In contrast, phytochrome B (PhyB) inhibits leaf senescence by repressing PIF4 and PIF5 at the post-translational level. Although we found how red light signaling represses leaf senescence in Arabidopsis, it remains unknown whether PhyB and/or PhyA are involved in leaf senescence in rice (Oryza sativa). Here we show that rice phyB knockout mutants (osphyB-1, -2, and -3) exhibited an early senescence phenotype during dark-induced senescence, but an osphyA knockout mutant (osphyA-3) senesced normally. The RT-qPCR analysis revealed that several senescence-associated genes, including OsORE1 and OsEIN3, were significantly up-regulated in osphyB-2 mutants, indicating that OsPhyB also inhibits leaf senescence, like Arabidopsis PhyB. We also found that leaf segments of osphyB-2 senesced faster even under light conditions. Supplementation with nitrogen compounds, such as KNO₃ and NH₄NO₃, rescued the early senescence phenotype of osphyB-2, indicating that starvation is one of the major signaling factors in the OsPhyB-dependent leaf senescence pathway.
authors.affiliation: Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea. vivianpanda622@gmail.com.
authors.forename: Weilan
authors.initials: W
authors.lastname: Piao
authors.affiliation: Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea. fndodpdy@snu.ac.kr.
authors.forename: Eun-Young
authors.initials: EY
authors.lastname: Kim
authors.affiliation: Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea. bebe86@snu.ac.kr.
authors.forename: Su-Hyun
authors.initials: SH
authors.lastname: Han
authors.affiliation: Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea. sakuraba0425@gmail.com.
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Sakuraba
authors.affiliation: Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea. ncpaek@snu.ac.kr.
authors.forename: Nam-Chon
authors.initials: NC
authors.lastname: Paek
keywords: dark-induced senescence; leaf senescence; phytochrome B; rice; starvation-induced senescence