ZmDof08, a zinc finger transcription factor, plays critical roles in photosynthesis in maize

Abstract

The gene ZmDof08, which underlies the yellow-green leaf mutant phenotype in maize, enhances the activity of key enzymes involved in C₄ photosynthesis, leading to a significant improvement in photosynthetic efficiency. Improving the photosynthetic efficiency of maize to increase its yield has long been a key focus in global agricultural research. Maize possesses a rich resource of leaf color mutants, which serve as valuable materials for studying leaf photosynthesis. The ygl4 mutant, characterized by yellow-green leaves and controlled by a recessive single gene, exhibits significant reductions in pigment content, net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr), along with abnormal chloroplast development. Through map-based cloning and gene editing techniques, we confirmed that the impaired function of the ZmDof08 gene is the fundamental cause of the ygl4 phenotype. ZmDof08 encodes a transcription factor located in the nucleus and is highly expressed in maize leaves, with its expression being light-induced. In the overexpression transgenic lines OE-15 and OE-23, the fresh weight of the aboveground parts of the seedlings significantly increased, the pigment content in the leaves was notably elevated, and the activities of key photosynthesis-related enzymes phosphoenolpyruvate carboxylase (PEPC), pyruvate orthophosphate dikinase (PPDK), NADP-dependent malic enzyme (NADP-ME), and NADP-dependent malate dehydrogenase (NADP-MDH) were also significantly enhanced. RNA-seq analysis revealed that ZmDof08 is implicated in the formation of the light-harvesting complex. This study provides a feasible path for the molecular design breeding of high photosynthetic efficiency maize varieties.

Keywords: ZmDof08; ygl4; Maize; Photosynthetic efficiency.