A two-locus interaction causes interspecific hybrid weakness in rice

Area of Science:

• Genetics
• Plant Biology
• Evolutionary Biology

Background:

• Reproductive barriers are crucial for speciation.
• Hybrid weakness, a postzygotic barrier, limits gene flow between species.
• Understanding the genetic basis of hybrid weakness is key to plant breeding and evolutionary studies.

Purpose of the Study:

• To identify the genetic factors responsible for high temperature-dependent hybrid weakness in interspecific rice hybrids.
• To elucidate the molecular mechanisms underlying this reproductive isolation.

Main Methods:

• Genetic analysis of interspecific rice hybrids.
• Gene cloning and characterization of LRR-RLK and subtilisin-like protease genes.
• Functional analysis of gene interactions and their effect on hybrid development.

Main Results:

• Two incompatible dominant loci, Hwi1 and Hwi2, were identified as key determinants of hybrid weakness.
• Hwi1 contains two LRR-RLK genes (25L1, 25L2) specific to wild rice (Oryza rufipogon).
• Hwi2, a rare allele in indica rice (Oryza sativa), encodes a secreted subtilisin-like protease.
• Combined Hwi1 and Hwi2 activate an autoimmune response, inhibiting root and shoot growth in hybrids.

Conclusions:

• The study reveals the genetic architecture of high temperature-dependent hybrid weakness in rice.
• The findings provide insights into reproductive isolation mechanisms in plants.
• This research may offer strategies for improving rice breeding by overcoming hybrid incompatibility.