S-RNase uptake by compatible pollen tubes in gametophytic self-incompatibility

Area of Science:

• Plant reproductive biology
• Molecular genetics
• Biochemistry

Background:

• Self-incompatibility (SI) is a genetic mechanism in flowering plants preventing inbreeding.
• The S-locus controls gametophytic self-incompatibility (GSI), leading to pollen rejection when pollen S-alleles match style S-alleles.
• S-RNases are the only known products of the S-locus, expressed in the style.

Purpose of the Study:

• To investigate the role of S-RNases in the pollen component of the self-incompatibility recognition system.
• To differentiate between two proposed models for pollen rejection: a gatekeeper model versus an inhibitor model.

Main Methods:

• Utilized immunocytochemical labeling techniques.
• Examined pollen tubes growing within the style of flowering plants.

Main Results:

• Detected accumulation of S-RNase within the cytoplasm of all pollen-tube haplotypes.
• This finding provides direct experimental evidence for the entry of S-RNases into pollen tubes.

Conclusions:

• The results experimentally support the inhibitor model of self-incompatibility.
• This model posits that pollen contains an inhibitor for non-cognate S-RNases, rather than a gatekeeper controlling entry.