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<p>Reproductive isolation between rice subspecies poses a significant barrier to harnessing heterosis in hybrid breeding. Here, we identified and characterized a novel locus, designated <i>Male Sterility-Related Hybrid Breakdown Locus on Chromosome 1</i> (<i>MSHB1</i>), through the utilization of chromosome segment substitution lines (CSSLs) derived from crosses between an <i>indica</i> cultivar Huanghuazhan (HHZ) and an <i>aromatic</i> cultivar Basmati Surkh 89 − 15 (BAS). A near-isogenic line, CS004, carrying the BAS-derived <i>MSHB1</i><sup><i>BAS</i></sup> allele, exhibits complete male sterility, reduced plant height, fewer panicles, and shorter panicle length. Fine mapping localized <i>MSHB1</i> to a 28.583-kb interval on the short arm of chromosome 1. Genetic complementation confirmed that the <i>MSHB1</i> allele from HHZ is sufficient to restore fertility. <i>MSHB1</i> encodes a homolog of Esa1-associated factor 6 (EAF6), which regulates histone acetylation and transcriptional activity. Comparative genomic analyses revealed that functional divergence in promoter activity between duplicated <i>OsEAF6</i> paralogs (<i>MSHB1</i> and <i>MSHB12</i>) drives hybrid breakdown. These findings elucidate a molecular mechanism underlying intersubspecific reproductive isolation and highlight <i>MSHB1</i> as a strategic target for overcoming hybrid sterility to enhance heterosis in rice breeding.</p>

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Fine mapping and cloning of an intersubspecific reproductive isolation locus MSHB1 in rice

  • 期刊论文

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  • 发表日期：

    2026年1月13日

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  • Xuan Wang,
  • Zhengjiu Zhang,
  • Jinfeng Zhao,
  • Mengjiao Chen,
  • Junyi Gong,
  • Yu Han,
  • Xin Wei,
  • Xuehui Huang,
  • Jiongjiong Fan

摘要

Reproductive isolation between rice subspecies poses a significant barrier to harnessing heterosis in hybrid breeding. Here, we identified and characterized a novel locus, designated Male Sterility-Related Hybrid Breakdown Locus on Chromosome 1 (MSHB1), through the utilization of chromosome segment substitution lines (CSSLs) derived from crosses between an indica cultivar Huanghuazhan (HHZ) and an aromatic cultivar Basmati Surkh 89 − 15 (BAS). A near-isogenic line, CS004, carrying the BAS-derived MSHB1BAS allele, exhibits complete male sterility, reduced plant height, fewer panicles, and shorter panicle length. Fine mapping localized MSHB1 to a 28.583-kb interval on the short arm of chromosome 1. Genetic complementation confirmed that the MSHB1 allele from HHZ is sufficient to restore fertility. MSHB1 encodes a homolog of Esa1-associated factor 6 (EAF6), which regulates histone acetylation and transcriptional activity. Comparative genomic analyses revealed that functional divergence in promoter activity between duplicated OsEAF6 paralogs (MSHB1 and MSHB12) drives hybrid breakdown. These findings elucidate a molecular mechanism underlying intersubspecific reproductive isolation and highlight MSHB1 as a strategic target for overcoming hybrid sterility to enhance heterosis in rice breeding.