Abstract
Rice yield is closely related to plant leaf shape and chlorophyll content. In this study, we isolated and identified a narrow and rolled leaf mutant, temporarily named nrl3 with darker green leaves. Histological analysis showed that nrl3 has a reduced number of vascular bundles and undergoes abnormal abaxial sclerenchymatous cell differentiation. The NRL3 mutant phenotype was controlled by a single recessive gene, fine-mapped to a 221 kb interval between Indel3 and RM2322 on Chr3. There are 42 ORF in this interval. Sequencing identified an SNP mutant leading to a premature stop in ORF 18, the candidate gene. Bioinformation analysis indicated that NRL3 encodes a novel protein with unknown function. NRL3 is localized in cytoplasm, membrane and nucleus. Expression analysis of nrl3 showed that genes involved in chlorophyll synthesis were significantly up-regulated while those involved in chlorophyll degradation and programmed cell death (PCD) were significantly down-regulated. The expression levels of photosynthesis genes were also affected. Y2H and BIFC assays indicated that NRL3 interacts directly with NAL9/VYL to regulate leaf morphology in rice. Thus, NRL3 plays an important role in leaf morphogenesis and chlorophyll accumulation, and can be used as a new gene resource for constructing improved rice.
Highlights
Rice is an important crop that provides nutrition and energy to the global population
Statistical analysis showed that the Leaf rolling index (LRI) of nrl3 (50%) was over three times that of wild-type (15%) (Figure 1E), and the flag leaf width of nrl3 was reduced by approximately 47% (Figure 1F)
Investigation of agronomic traits revealed no obvious differences in the plant height and effective tillers number between wild-type and nrl3 (Supplementary Figures S1A,C), but panicle length was significantly decreased in nrl3 (Figure 1B and Supplementary Figure S1B)
Summary
Rice is an important crop that provides nutrition and energy to the global population. The global demand for rice has increased quickly, but production has risen by less than 1%. Increasing rice yield is the ultimate goal of rice breeding. Rice leaf is the main photosynthesis organ. Leaf shape affects the efficiency of light capture and energy conversion. Appropriate leaf shape can improve plant photosynthesis efficiency and increase plant yield (Tsukaya, 2006; Micol, 2009)
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