S-RNases and sexual incompatibility: structure, functions, and evolutionary perspectives

Area of Science:

• Plant reproductive biology
• Molecular evolution
• Genetics

Background:

• S-RNase-based gametophytic self-incompatibility is a widespread breeding barrier in angiosperms, notably in Solanaceae, Scrophulariaceae, and Rosaceae.
• This system is governed by a single genetic locus (S) and involves pistil-expressed S-RNases in self-pollen rejection.
• The pollen component of this recognition mechanism remains unidentified.

Purpose of the Study:

• To review current knowledge on the structure, function, and evolution of S-RNases and S-loci.
• To present new phylogenetic analyses of S-RNases.
• To discuss the implications of findings on S-RNase variability and evolution.

Main Methods:

• Review of existing literature on S-RNase-based self-incompatibility.
• Phylogenetic analysis of S-RNase sequences.
• Comparative analysis of sequence variability and evolutionary pressures.

Main Results:

• Sequence variability among S-alleles is distributed throughout the S-RNase gene, not confined to specific regions.
• Evidence suggests recombination and/or diversifying selection acting on at least two distinct regions of S-RNases.
• The findings challenge previous assumptions about the localization of sequence variation.

Conclusions:

• The study provides new insights into the evolutionary dynamics of S-RNase genes.
• Understanding S-RNase variability is crucial for comprehending the evolution of self-incompatibility in plants.
• Further research is needed to identify the pollen component of the S-RNase recognition system.