A distorter-restorer system drives quantitative reproductive isolation in rice

Area of Science:

• Genetics
• Plant Biology
• Evolutionary Biology

Background:

• Hybrid sterility and segregation distortion are key reproductive isolation barriers in rice.
• The molecular mechanisms underlying quantitative variation in these traits are not fully understood.

Purpose of the Study:

• To identify and characterize the genetic basis of hybrid male sterility and segregation distortion in rice.
• To investigate the role of the S44 distorter-restorer system in reproductive isolation between Oryza longistaminata and Asian cultivated rice.

Main Methods:

• Identification of the S44 locus and its four linked elements: Reproductive Isolation Distorter (RID), Reproductive Isolation Restorer (RIR), Reproductive Isolation Activator (RIA), and Reproductive Isolation Suppressor (RIS).
• Analysis of gamete elimination and preferential transmission in hybrids.
• CRISPR-Cas9 gene editing to knockout the RID element.

Main Results:

• The S44 system comprises RID, RIR, RIA, and RIS, which collectively regulate hybrid male sterility and segregation distortion.
• RID eliminates O. sativa RD23 pollen, while RIR protects O. longistaminata gametes, leading to skewed allele transmission.
• CRISPR-mediated knockout of RID universally resolved S44-mediated reproductive barriers in AA genome rice hybrids.

Conclusions:

• Allelic conflicts at the S44 locus drive quantitative reproductive isolation between rice lineages.
• The S44 distorter-restorer system offers a genetic module for understanding speciation.
• Targeting RID presents a strategy for overcoming cross-species breeding barriers in rice.