On the origin of self-incompatibility haplotypes: transition through self-compatible intermediates

Area of Science:

• Plant reproductive biology
• Evolutionary genetics
• Molecular genetics

Background:

• Self-incompatibility (SI) is a genetic mechanism preventing self-fertilization in flowering plants.
• In Solanaceae, Rosaceae, and Scrophulariaceae, SI involves pistil S-RNase and pollen-S genes.
• The S-locus controls SI, with S-RNase and pollen-S genes determining specificity.

Purpose of the Study:

• To investigate the evolutionary pathways for the origin of new self-incompatibility specificities.
• To analyze the role of mutations in S-RNase and pollen-S genes in SI evolution.
• To determine the conditions favoring the generation of novel SI specificities.

Main Methods:

• Evolutionary analysis of mutations affecting pistil and pollen specificity.
• Modeling the effects of mutation rates and viability on SI evolution.
• Investigating the genetic basis of S-RNase and pollen-S interactions.

Main Results:

• Natural selection favors pollen-S mutations that decrease pollen acceptance range.
• Mutations in S-RNase leading to non-reciprocal pollen acceptance are disfavored.
• A pathway exists for generating new SI specificities via partial SI breakdown and restoration.

Conclusions:

• New SI specificities require mutations in both S-RNase and pollen-S genes.
• Evolutionary dynamics favor specific types of mutations to generate novel SI systems.
• Understanding these pathways is crucial for plant breeding and conservation efforts.