| 摘 要： |
Breakdown of self-incompatibility has frequently been attributed to loss-of-function mutations of alleles at the locus responsible for recognition of self-pollen (i.e. the S-locus). However, other potential causes have rarely been tested. Here, we show that self-compatibility of S1S1-homozygotes in selfing populations of the otherwise self-incompatible Arabidopsis lyrata is not due to S-locus mutation. Between-breeding-system cross-progeny are self-compatible if they combine S-1 from the self-compatible cross-partner with recessive S-1 from the self-incompatible cross-partner, but self-incompatible with dominant S-alleles. Because S1S1 homozygotes in outcrossing populations are self-incompatible, mutation of S-1 cannot explain self-compatibility in S1S1 cross-progeny. This supports the hypothesis that an S-1-specific modifier unlinked to the S-locus causes self-compatibility by functionally disrupting S-1. Self-compatibility in S19S19 homozygotes may also be caused by an S-19-specific modifier, but we cannot rule out a loss-of-function mutation of S-19. Taken together, our findings indicate that breakdown of self-incompatibility is possible without disruptive mutations at the S-locus. |
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