Evolutionary relationships among self-incompatibility RNases
- Section of Ecology, Behavior, and Evolution, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093
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Edited by Barbara A. Schaal, Washington University, St. Louis, MO, and approved September 7, 2001 (received for review July 25, 2001)
Abstract
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 ≈75% of dicot families, our results indicate that RNase-based self-incompatibility was the ancestral state in the majority of dicots.
Footnotes
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↵ † To whom reprint requests should be addressed. E-mail: bigic{at}ucsd.edu.
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This paper was submitted directly (Track II) to the PNAS office.
- Abbreviations:
- S-RNase,
- self-incompatibility RNase;
- GSI,
- gametophytic self-incompatibility;
- MP,
- maximum parsimony;
- NJ,
- neighbor joining;
- ML,
- maximum likelihood;
- RASA,
- relative apparent synapomorphy analysis
- Copyright © 2001, The National Academy of Sciences
