Characterization and fine mapping of the rice gene OsARVL4 regulating leaf morphology and leaf vein development

Leaf morphology and chlorophyll content are closely related to the photosynthetic efficiency, which would potentially contribute to crop yield. In this study, we isolated an EMS-mutagenized rice mutant displaying abaxial rolling and vein-albino leaves, and thus designated it as Osarvl4. Compared to the wild type ‘Nipponbare’, Osarvl4 mutant had abnormal development of clear cells, parenchyma cells, sclerenchymatous cells, mesophyll cells, bulliform cells and vascular bundles. As a result of the defective leaf development, the chlorophyll content and photosynthetic efficiency were significantly affected in the mutant. Genetic analysis using map-based cloning indicated that the mutation was controlled by a single recessive karyogene localized within a 44 kb region on the long arm of chromosome 4. Sequence analysis and alignment indicated that the three candidate genes in this region showed no difference at the DNA level. However, quantitative real-time PCR analysis showed that the expression of the LOC_Os04g33580 gene in the mutant was significantly lower than that of wild type, while expression of the other two candidate genes (LOC_Os04g33560 and LOC_Os04g33570) exhibited no significant difference. Therefore, we speculate that LOC_Os04g33580 might be the target gene which regulates leaf vein development and leaf morphogenesis in rice and this locus might be subject to epigenetic regulation, such as DNA methylation, Thus, our finding suggests that the OsARVL4 gene is involved in the regulation of chlorophyll content and photosynthetic efficiency in plants, and provides a genetic basis for the future study of genes related to leaf development in rice.