Rice bZIP11 acts as a transcriptional repressor that negatively regulates photosynthesis in response to nitrogen deficiency

Nitrogen (N)-deficiency responses, which are closely linked to plant biomass and crop yield, differ between plant tissues. A previous in silico analysis suggested that four transcription factors, including OsbZIP11, play vital roles in the gene regulatory network governing N-deficiency responses (NDRs) in rice roots. To investigate the role of OsbZIP11 in NDRs, the phenotypes, functional responses, and gene expression of rice plants that either lacked functional OsbZIP11 or overexpressed OsbZIP11 were analyzed. Contrary to expectations, OsbZIP11 function showed an overwhelmingly stronger association with photosynthetic gene expression than with any other physiological process, including the expression control of N-related genes. OsbZIP11 directly suppressed numerous photosynthetic genes as a transcriptional repressor. N deficiency increased OsbZIP11 expression in shoots, consistent with N deficiency-reduced photosynthetic activity. Furthermore, removing functional OsbZIP11 and OsbZIP11 overexpression produced opposite effects on the expression of genes involved in the light-dependent reactions of photosynthesis and carbon dioxide fixation, as well as on growth and grain yield. These findings indicate that OsbZIP11 is a critical factor responsible for N deficiency-induced decreases in photosynthesis in rice and provide new insights into the mechanism underlying the coordination of C and N acquisition.