Rice Science

Rice Science

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Genome-Wide Identification of Myeloblastosis (MYB) Family and Functional Characterization of OsMYB2-18 in Regulating Grain Length in Rice

  1. Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding / Zhongshan Biological Breeding Laboratory / Key Laboratory of Plant Functional Genomics of the Ministry of Education, Agricultural College of Yangzhou University, Yangzhou 225009, China; Jiangsu Co-Innovation Center for Modern Production Technology of Grain Crops / Jiangsu Key Laboratory of Crop Genetics and Physiology, Yangzhou University, Yangzhou 225009, China; Yangzhou Modern Seed Innovation Institute, Gaoyou 225600, China; Joint International Research Laboratory of Agriculture and Agri-Product Safety, the Ministry of Education of China, Yangzhou University, Yangzhou 225009, China; These authors contributed equally to this work
  • Contact: LENG Yujia ; LIU Qiaoquan ; GAO Jiping
  • Supported by:
    This study was supported by the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No. 22KJA210003), the National Key Research and Development Program of China (Grant No. 2022YFD1200103), the Jiangsu Province Government in China (Grant No. BE2022336), the Project of Zhongshan Biological Breeding Laboratory, China (Grant No. ZSBBL-KY2023-01), the open funds of the Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding, China (Grant No. PL202403), and the Priority Academic Program Development of Jiangsu Higher Education Institutions, China. We thank Professors Li Xueyong and Fang Jingjing (Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, China) for kindly providing the pGreenII 0800-LUC-GW8 vector, and Professor Sun Shengyuan (Yangzhou University, China) for kindly providing the genotype data of the rice germplasm.

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Abstract: MYB transcription factors constitute one of the largest gene families in plants and play important roles in growth and developmental regulation; however, their functions in rice seed development remain incompletely understood. This study performed a genome-wide identification of 245 MYB transcription factor genes in rice, analyzing their chromosomal distribution, phylogenetic relationships, gene duplications, cis-regulatory elements, and expression profiling across various tissues and developmental stages. OsMYB2-18, a highly expressed gene during seed development, was selected for functional characterization. The loss of OsMYB2-18 function results in a significant increase in grain length and 1000-grain weight compared with wild-type plants. Histological analysis via scanning electron microscopy revealed that this long-grain phenotype is primarily driven by enhanced cell expansion in the spikelet hull. OsMYB2-18 was highly expressed in leaf sheaths and young inflorescences, and its encoded protein localizes in the nucleus. As a transcriptional activator, OsMYB2-18 enhances the transcriptional level of the downstream target gene GW8. Furthermore, haplotype analysis of 4 702 rice accessions identified 3 distinct haplotypes (Hap I‒Hap III) with significant subspecies specificity. Nucleotide diversity analysis indicated that OsMYB2-18 has undergone strong artificial selection in indica and japonica populations during domestication. These findings suggest that OsMYB2-18 serves as a valuable genetic resource for the molecular breeding of high-yielding rice varieties with optimized grain morphology.

Key words: Oryza sativa, MYB transcription factor, OsMYB2-18, grain length, seed development, haplotype analysis