The bHLH transcription factor OsPRI1 activates the Setaria viridis PEPC1 promoter in rice

Journal article

• Photosynthetic efficiency is reduced by the dual role of Rubisco, which acts either as a carboxylase or as an oxygenase, the latter leading to photorespiration. C₄ photosynthesis evolved as a carbon-concentrating mechanism to reduce photorespiration. To engineer C₄ into a C₃ plant, it is essential to understand how C₄ genes, such as phosphoenolpyruvate carboxylase (PEPC1), are regulated to be expressed at high levels and in a cell-specific manner.
• Yeast one-hybrid screening was used to show that OsPRI1, a rice bHLH transcription factor involved in iron homeostasis, binds to the Setaria viridis PEPC1 promoter. This promoter drives mesophyll-specific gene expression in rice. The role of OsPRI1 in planta was characterized using a rice line harbouring SvPEPC1_pro::GUS.
• We show that OsPRI1 activates the S. viridis PEPC1 promoter by binding to an N-box in the proximal promoter, and that GUS activity is highly reduced in SvPEPC1_pro::GUS lines when OsPRI1 is mutated. Cross-species comparisons showed that the SvPRI1 homolog binds to the SvPEPC1 promoter but the maize ZmPRI1 does not bind to the ZmPEPC1 promoter.
• Our results suggest that elements of the iron homeostasis pathway were co-opted to regulate PEPC1 gene expression during the evolution of some but not all C₄ species.

Authors: Carvalho, P; Gomes, C; Gonçalves, I; Lourenço, TF; Vlad, D

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Wiley
• Journal: New Phytologist
• Volume: 241
• Issue: 6
• Pages: 2495-2505
• Publication date: 2024-02-07
• Acceptance date: 2023-12-29
• DOI: 10.1111/nph.19556
• EISSN: 1469-8137
• ISSN: 0028-646X
• Language: English
• Keywords: transcriptional regulation; rice; cell-specific gene expression; C4 photosynthesis; phosphoenolpyruvate carboxylase