LAUSR

In rice, moderate leaf rolling improves photosynthesis and crop yield. However, the molecular mechanisms underlying this important agronomic trait remain incompletely understood. Here, we investigated a dominant rolled leaf mutant (RL-D) developed from Nipponbare rice (WT). From the six-leaf stage, the leaves of the mutant rolled inward, and abnormal sclerenchyma tissues developed on the abaxial side of the leaf midribs. Additionally, leaf length, plant height, grain weight, and chlorophyll content were significantly greater in the mutant as compared to the WT. Genetic mapping analysis suggested that the leaf-rolling trait in the RL-D mutant was controlled by a single dominant gene, which was located in a 743-kb region on rice chromosome 3. Re-sequencing analysis showed that one gene in the mapped region encoding a protein phosphatase, Os03g0395100 (herein designated OsPP2C), had base mutations in the first exon. These mutations may have produced a truncated form of the OsPP2C protein in RL-D. Further transcriptomic analysis revealed that several biological processes, especially secondary cell wall formation and protein phosphorylation, were overrepresented among the differentially expressed genes (DEGs) between the mutant and the wild type. qRT-PCR verification also demonstrated that specific genes associated with leaf polarity and secondary cell wall formation were differentially expressed in the mutant. This study presents a novel dominant rolled-leaf germplasm that may help to improve rice leaf morphology in the future. The results also suggested that the RL-D phenotype might result from abnormal sclerenchyma tissue development, possibly regulated by OsPP2C via the dephosphorylation pathway. This may present a novel mechanism underlying leaf-rolling in rice.