Insights into the evolution of self-compatibility in Lycopersicon from a study of stylar factors.
To elucidate the molecular basis of loss of self-incompatibility in Lycopersicon, S-RNases and HT-proteins were analysed in seven self-compatible (SC) and three self-incompatible (SI) taxa. No or low stylar RNase activity was a common feature in most SC taxa examined, in contrast to the uniformly high levels of activity found in all SI species. The S-RNase gene is most likely deleted in the four red-fruited SC taxa (L. esculentum, L. esculentum var. cerasiforme, L. pimpinellifolium and L. cheesmanii) because S-RNase genes could not be amplified from genomic DNA. S-RNase genes could, however, be amplified from the genomes of the three green-fruited SC taxa examined. L. chmielewskii and L. hirsutum f. glabratum show a decreased accumulation of transcripts, possibly reflecting changes in the 5' flanking regions of the S-RNase genes. The remaining green-fruited SC species, L. parviflorum, has a functional S-RNase gene in its genome that is expressed at high levels in the style, suggesting a genetic factor responsible for the low S-RNase activity. Together these results argue for several independent mutations in the S-RNase gene over the course of Lycopersicon diversification, and that loss of S-RNase function is unlikely to the primary cause of the loss of self-incompatibility. We also examined the HT-B genes that play a role in self-incompatibility. HT-B transcripts were markedly reduced in the styles of all the SC taxa examined. A scenario is described where a mutation causing reduced transcription of HT-B in an ancestral SI species was central to the loss of self-incompatibility in Lycopersicon.
Kondo
Katsuhiko
K
Faculty of Bioresources, Mie University, Tsu 514-8507, Japan.
Yamamoto
Mayu
M
Itahashi
Ryoko
R
Sato
Takanori
T
Egashira
Hiroaki
H
Hattori
Tsukaho
T
Kowyama
Yasuo
Y
D005075:Biological Evolution; D019143:Evolution, Molecular; D005298:Fertility / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics*; D018551:Solanum lycopersicum / Q000145:classification / Q000201:enzymology / Q000235:genetics* / Q000502:physiology*; D009154:Mutation / Q000235:genetics; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D012260:Ribonucleases / Q000235:genetics*; D014158:Transcription, Genetic
C400763:HT protein, Nicotiana alata; D010940:Plant Proteins; D018749:RNA, Plant; D012260:Ribonucleases; C022542:ribonuclease S