Hui Dong, Jie Lei, Yunlu Tian, Juan Liu, Hang Yang, Xiaokang Jiang, Rushuang Zhang, Yu Zhang, Rongbo Chen, Yiqun Bao, Feng Liu, Yulong Ren, Yaping Lu, Xi Liu, Shijia Liu, Xue Yang, Erchao Duan, Xuan Teng, Yunlong Wang, Chuanwei Gu, Yipeng Zhang, Xiaoli Chen, Yunpeng Zhang, Hongyi Xu, Rui Sha, Xia Xu, Ruomeng Li, Gongyu Li, Yihua Wang, Jianmin Wan

PNAS; 2026; IF: 9.10

DOI: 10.1073/pnas.2519395123

Abstract

D-amino acids are key components of the bacterial cell wall and play important roles in neural communication and inflammatory responses in animals. However, knowledge about D-amino acid metabolism and physiological functions in plants is limited. Here, we isolated and characterized a rice D-amino acid aminotransferase1, OsDAAT1, which maternally regulates rice grain chalkiness through map-based cloning and a subsequent complementation test. We found that OsDAAT1 is highly expressed in the vascular tissue of rice nodes and is capable of interconverting different D-amino acids in vitro. Mutation of OsDAAT1 results in elevated D-alanine levels in stems, nodes, and developing grains. The disruption of D-amino acid metabolism subsequently leads to significantly altered peptide/protein isomerization, including some key enzymes involved in starch and protein biosynthesis. These changes trigger severe endoplasmic reticulum stress and ultimately leads to chalky grains. Furthermore, we identified OsDAAT1^Hap1as a low-chalkiness haplotype, and historical frequency analysis suggests that OsDAAT1 may have undergone selection during rice domestication. Overall, our findings uncover a previously unrecognized role in D-amino acid metabolism in plants and facilitate the practical use of OsDAAT1 in grain appearance quality improvement in rice.