Characterization of a Novel Rice Dynamic Narrow-Rolled Leaf Mutant with Deficiencies in Aromatic Amino Acids

• Main Authors: Huimei Wang, Yongfeng Shi, Xiaobo Zhang, Xia Xu, Jian-Li Wu
• Format: Article
• Language: English
• Published: MDPI AG 2020-02-01
• Series: International Journal of Molecular Sciences
• Subjects: narrow-rolled leaf; dahps; map-based cloning; rice (<i>oryza sativa</i> l.)
• Online Access: https://www.mdpi.com/1422-0067/21/4/1521

The leaf blade is the main photosynthetic organ and its morphology is related to light energy capture and conversion efficiency. We isolated a novel rice <i>Dynamic Narrow-Rolled Leaf 1</i> (<i>dnrl1</i>) mutant showing reduced width of leaf blades, rolled leaves and lower chlorophyll content. The narrow-rolled leaf phenotype resulted from the reduced number of small longitudinal veins per leaf, smaller size and irregular arrangement of bulliform cells compared with the wild-type. <i>DNRL1</i> was mapped to chromosome 7 and encoded a putative 3-deoxy-7-phosphoheptulonate synthase (DAHPS) which catalyzes the conversion of phosphoenolpyruvate and D-erythrose 4-phosphate to DAHP and phosphate. Sequence analysis revealed that a single base substitution (T&#8722;A) was detected in <i>dnrl1</i>, leading to a single amino acid change (L376H) in the coding protein. The mutation led to a lower expression level of <i>DNRL1</i> as well as the lower activity of DAHPS in the mutant compared with the wild type. Genetic complementation and over-expression of <i>DNRL1</i> could rescue the narrow-rolled phenotype. <i>DNRL1</i> was constitutively expressed in all tested organs and exhibited different expression patterns from other narrow-rolled leaf genes. DNRL1-GFP located to chloroplasts. The lower level of chlorophyll in <i>dnrl1</i> was associated with the downregulation of the genes responsible for chlorophyll biosynthesis and photosynthesis. Furthermore, <i>dnrl1</i> showed significantly reduced levels of aromatic amino acids including Trp, Phe and Tyr. We conclude that OsDAHPS, encoded by <i>DNRL1</i>, plays a critical role in leaf morphogenesis by mediating the biosynthesis of amino acids in rice.