The Prunus self-incompatibility locus (S locus) is seldom rearranged

Area of Science:

• Plant reproductive biology
• Molecular genetics
• Evolutionary biology

Background:

• Self-incompatibility (SI) is crucial for preventing self-pollination in flowering plants.
• In Prunus, SI specificity is governed by two genes: S-RNase (pistil determinant) and SFB (pollen determinant).
• The relative transcription orientation of these SI genes has been studied, with a common pattern observed, except for a specific haplotype in Prunus armeniaca.

Purpose of the Study:

• To investigate the transcription orientation of S-RNase and SFB genes in the Prunus armeniaca S(17) haplotype.
• To determine if the transcription orientation of the P. armeniaca S(2) haplotype is representative of all haplotypes within the species.
• To analyze the evolutionary conservation of transcription orientation for these SI genes in Prunus.

Main Methods:

• Phylogenetic analysis of S-RNase and SFB gene transcription orientation.
• Comparative genomics of SI gene loci across Prunus species.
• Examination of gene transcription orientation in the Prunus armeniaca S(17) haplotype.

Main Results:

• The Prunus armeniaca S(17) haplotype exhibits the commonly observed opposite transcription orientation for S-RNase and SFB genes.
• The transcription orientation of the P. armeniaca S(2) haplotype is not representative of all haplotypes in the species.
• Phylogenetic analysis indicates that the relative transcription orientation of S-RNase and SFB genes is highly conserved in Prunus, with rare changes over evolutionary time.

Conclusions:

• The study refutes the postulate that the transcription orientation of the P. armeniaca S(2) haplotype is universal for the species.
• The conserved transcription orientation of S-RNase and SFB genes in Prunus highlights its evolutionary stability.
• This contrasts with the greater lability of gene arrangement observed at the Brassica sporophytic S locus.