NATIONL CENTER OF PLANT GENE RESEARCH(WUHAN)
A Killer-Protector System Regulates Both Hybrid Sterility and Segregation Distortion in Rice
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A Killer-Protector System Regulates Both Hybrid Sterility and Segregation Distortion in Rice

  1. Qifa Zhang1,

+Author Affiliations

  1. 1National Key Laboratory of Crop Genetic Improvement and National Centre of Plant Gene Research, Huazhong Agricultural University, Wuhan 430070, China.
  2. 2School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong 999077, China.
  1. To whom correspondence should be addressed. E-mail: qifazh@mail.hzau.edu.cn
  1. * These authors contributed equally to this work.

ABSTRACT

Hybrid sterility is a major form of postzygotic reproductive isolation that restricts gene flow between populations. Cultivated rice (Oryza sativa L.) consists of two subspecies, indica and japonica; inter-subspecific hybrids are usually sterile. We show that a killer-protector system at the S5 locus encoded by three tightly linked genes [Open Reading Frame 3 (ORF3) to ORF5] regulates fertility in indica-japonicahybrids. During female sporogenesis, the action of ORF5+ (killer) and ORF4+ (partner) causes endoplasmic reticulum (ER) stress. ORF3+ (protector) prevents ER stress and produces normal gametes, but ORF3– cannot prevent ER stress, resulting in premature programmed cell death and leads to embryo-sac abortion. Preferential transmission of ORF3+ gametes results in segregation distortion in the progeny. These results add to our understanding of differences between indica and japonica rice and may aid in rice genetic improvement.