Evolutionary relationships among self-incompatibility RNases.
T2-type RNases are responsible for self-pollen recognition and rejection in three distantly related families of flowering plants-the Solanaceae, Scrophulariaceae, and Rosaceae. We used phylogenetic analyses of 67 T2-type RNases together with information on intron number and position to determine whether the use of RNases for self-incompatibility in these families is homologous or convergent. All methods of phylogenetic reconstruction as well as patterns of variation in intron structure find that all self-incompatibility RNases along with non-S genes from only two taxa form a monophyletic clade. Several lines of evidence suggest that the best interpretation of this pattern is homology of self-incompatibility RNases from the Scrophulariaceae, Solanaceae, and Rosaceae. Because the most recent common ancestor of these three families is the ancestor of approximately 75% of dicot families, our results indicate that RNase-based self-incompatibility was the ancestral state in the majority of dicots.
Igic
B
B
Section of Ecology, Behavior, and Evolution, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA. bigic@ucsd.edu
Kohn
J R
JR
D004722:Endoribonucleases / Q000235:genetics*; D019143:Evolution, Molecular; D019684:Magnoliopsida / Q000201:enzymology / Q000235:genetics; D010802:Phylogeny
D004722:Endoribonucleases; C022543:ribonuclease T(2)