Phytochrome B Negatively Affects Cold Tolerance by Regulating OsDREB1 Gene Expression through Phytochrome Interacting Factor-Like Protein OsPIL16 in Rice

Abstract

Cross talk between light signaling and cold signaling has been elucidated in the model plant Arabidopsis and tomato, but little is known about their relationship in rice. Here, we report that phytochrome B (phyB) mutants exhibit improved cold tolerance compared with wild type (WT) rice (Oryza sativa L. cv. Nipponbare). The phyB mutants had a lower electrolyte leakage index and malondialdehyde concentration than the WT, suggesting that they had greater cell membrane integrity and less lipid peroxidation. Real-time PCR analysis revealed that the expression levels of dehydration-responsive element binding protein 1 (OsDREB1) family genes, which functions in the cold stress response in rice, were increased in the phyB mutant under normal and cold stress conditions. PIFs are central players in phytochrome-mediated light signaling networks. To explore the relationship between rice PIFs and OsDREB1 gene expression, we produced overexpression lines of rice PIF genes. OsDREB1 family genes were up-regulated in OsPIL16-overexpression lines, which had improved cold tolerance relative to the WT. Chromatin immunoprecipitation (ChIP)-qPCR assay revealed that OsPIL16 can bind to the N-box region of OsDREB1B promoter. Expression pattern analyses revealed that OsPIL16 transcripts were induced by cold stress and was significantly higher in the phyB mutant than in the WT. Moreover, yeast two-hybrid assay showed that OsPIL16 can bind to rice PHYB. Based on these results, we propose that phyB deficiency positively regulates OsDREB1 expression through OsPIL16 to enhance cell membrane integrity and to reduce the malondialdehyde concentration, resulting in the improved cold tolerance of the phyB mutants.

Molecular mechanisms underlying stress response and adaptation

“…PhyB negatively regulates chloroplast structural stability by lowering levels of unsaturated fatty acids present in membrane lipids . PhyB deficiency positively regulates OsPIL16 and OsDREB1 , thereby alleviating chilling‐induced photoinhibition and enhancing chilling tolerance . Similar mechanisms have also been characterized in Suaeda salsa .…”

Cold signaling in plants: Insights into mechanisms and regulation

“…In rice, phyB mutants exhibit enhanced chilling tolerance. A recent study established that OsPIL16 positively regulates expression of OsDREB1 , which could enhance cell membrane integrity and reduce malondialdehyde concentration in these phyB mutants (He et al ). It was also reported that phyB interacts with phytochrome‐interacting factor 4 (PIF4) and PIF7 to repress expression of the CBF pathway and freezing tolerance under long‐day (LD) conditions.…”

The basic helix‐loop‐helix transcription factor, OsPIL15, regulates grain size via directly targeting a purine permease gene OsPUP7 in rice

“…Transcription factors regulate gene expression by binding to their promoters, thereby promoting or inhibiting their subsequent transcription. A previous study revealed that PIF3 binds to the Gbox (CACGTG) or PBE-box (CACATG), while OsPIF14 and OsPIL16 bind to the N-box [CACG(C/A)G] (Cordeiro et al, 2016;He et al, 2016;Zhang et al, 2013). Based on these findings, an electrophoresis mobility shift assay (EMSA) was performed to identify the specific DNA sequences to which OsPIL15 binds.…”