S-RNase-based self-incompatibility in Petunia inflata

Area of Science:

• Plant reproductive biology
• Molecular genetics
• Biochemistry

Background:

• Solanaceae-type self-incompatibility (SI) relies on polymorphic S-locus genes: S-RNase (pistil specificity) and S-locus F-box (SLF/SFB) (pollen specificity).
• This review focuses on Petunia inflata as a model system to study SI mechanisms.

Purpose of the Study:

• To summarize recent findings on S-RNase and SLF identification and function.
• To propose and explain a protein-degradation model for self-pollen tube rejection.

Main Methods:

• Review of experimental work from the authors' laboratory.
• Functional studies of S-RNase and SLF genes in Petunia inflata.
• Comparative analysis of SLF/SFB gene evolution and function across plant families.

Main Results:

• The proposed protein-degradation model explains compatible/incompatible pollination and competitive interactions.
• Multiple SLF/SFB-like genes exist in Solanaceae, Plantaginaceae, and Maloideae Rosaceae, but their pollen S-gene function is not confirmed.
• Subfamily Prunoideae Rosaceae has a single SLF/SFB gene and lacks competitive interaction.

Conclusions:

• S-RNase cytotoxic function is crucial for SI in Solanaceae, Plantaginaceae, and Rosaceae.
• SLF/SFB function may have diverged, indicating the complexity of S-RNase-based SI.
• Further experiments are needed to fully elucidate this self/non-self discrimination mechanism.