SRG1, Encoding a Kinesin-4 Protein, Is an Important Factor for Determining Grain Shape in Rice

摘要

Grain shape is one of the important agronomic traits, which is closely related to the yield of rice. A new rice mutant, namedsmall and round grain(srg1), was isolated from anindicacultivar Zhenong 34 by ethyl methane sulfonate (EMS) mutagenesis. The microscopic analysis showed that the cell length of spikelet insrg1was decreased compared with that in wild type (WT), which caused the grain length short. Meanwhile, the grains ofsrg1were wider than those of WT because of the increased cell layers in spikelet in the lateral direction. Therefore, the inhibition of cell expansion and increased cell proliferation collectively led to the small and round grain. By map-based cloning, the geneSRG1was located on the short arm of chromosome 9, which encodes a kinesin-4 protein, represented by the gene LOC_Os09g02650.A single nucleotide polymorphism, occurred in the 16th exon ofSRG1, led to premature translation stop in mutant. The cell cycle-related genes were up-regulated insrg1, which conferred thatSRG1controlled grain width through the cell proliferation. Since the role ofSRG1in regulating grain shape was not clarified well before, it is valuable to explore the mechanism of grain development. This study could, hence, provide a morphogenesis and molecular basis for elucidating the function ofSRG1, as well as a new germplasm resource for the further study of grain development.