A genotype-specific pollen gene associated with self-incompatibility in Lycopersicon peruvianum

Self-incompatibility is a genetically controlled process used to prevent self-pollination. We report here the characterization of pollen cDNA clones of Lycopersicon peruvianum, and the identification of a genotype-specific pollen factor involved in self-incompatibility. To identify the latter, differential mRNA display RT-PCR was performed on pollen cDNAs from S₁₂S _a and S₁₁S_a genotypes. We isolated four cDNA fragments expressed preferentially in S₁₂S₃ pollen, and screened a cDNA library from S₁₂S₃ pollen with the four cDNA fragments to isolate the corresponding full length cDNAs. One of the four isolated cDNAs encoded part of an actin depolymerizing factor protein that we named LpADF. LpADF is highly homologous to actin depolymerizing factors of Arabidopsis thaliana, Lilium longiflorum, and Zea mays. RNA blot analysis revealed that LpADF is only expressed in mature pollen of the S ₁₂S_a genotype, and is therefore a candidate pollen factor in the gametophyte self-incompatibility system of L. peruvianum.