S-RNase-based self-incompatibility in angiosperms: Degradation, condensation, and evolution.

Area of Science:

• Plant reproductive biology
• Molecular genetics
• Evolutionary biology

Background:

• Self-incompatibility (SI) systems in flowering plants (angiosperms) prevent self-pollination, promoting genetic diversity.
• The S-RNase-based SI system is regulated by pistil S-RNases and pollen S-locus F-box (SLF) proteins, controlled by a multiallelic S-locus.

Purpose of the Study:

• To review the molecular mechanisms and evolutionary origins of the S-RNase-based SI system.
• To highlight the role of SI in plant reproduction and its implications for agricultural breeding.

Main Methods:

• Review of existing literature on S-RNase and SLF protein interactions.
• Analysis of the evolutionary linkage of S-RNase and SLF genes.
• Discussion of the molecular events in cross- and self-pollination.

Main Results:

• In cross-pollination, SLF proteins form SCF ubiquitin ligase complexes that degrade non-self S-RNases, enabling fertilization.
• In self-pollination, S-RNases escape degradation, form cytoplasmic condensates, disrupt cellular processes, and trigger programmed cell death.
• The S-RNase-based SI system is considered ancestral, likely evolving from linked S-RNase and SLF genes.

Conclusions:

• The S-RNase-based SI system is a sophisticated mechanism crucial for plant reproduction and genetic diversity.
• Understanding SI mechanisms is vital for improving crop breeding strategies.
• Future research should focus on SLF-S-RNase recognition, S-locus genetics, and novel SI systems.