Style-by-style analysis of two sporadic self-compatible Solanum chacoense lines supports a primary role for S-RNases in determining pollen rejection thresholds.
A method for the quantification of S-RNase levels in single styles of self-incompatible Solanum chacoense was developed and applied toward an experimental determination of the S-RNase threshold required for pollen rejection. It was found that, when single style values are averaged, accumulated levels of the S(11)- and S(12)-RNases can differ up to 10-fold within a genotype, while accumulated levels of the S(12)-RNase can differ by over 3-fold when different genotypes are compared. Surprisingly, the amount of S(12)-RNase accumulated in different styles of the same plant can differ by over 20-fold. A low level of 160 ng S-RNase in individual styles of fully incompatible plants, and a high value of 68 ng in a sporadic self-compatible (SSC) line during a bout of complete compatibility was measured, suggesting that these values bracket the threshold level of S-RNase needed for pollen rejection. Remarkably, correlations of S-RNase values to average fruit sets in different plant lines displaying sporadic self-compatibility (SSC) to different extents as well as to fruit set in immature flowers, are all consistent with a threshold value of 80 ng S(12)-RNase. Taken together, these results suggest that S-RNase levels alone are the principal determinant of the incompatibility phenotype. Interestingly, while the S-RNase threshold required for rejection of S(12)-pollen from a given genetic background is the same in styles of different genetic backgrounds, it is different when pollen donors of different genetic backgrounds are used. These results reveal a previously unsuspected level of complexity in the incompatibility reaction.
Qin
Xike
X
IRBV, Biology Department, University of Montreal, Canada.
Liu
Bolin
B
Soulard
Jonathan
J
Morse
David
D
Cappadocia
Mario
M
D035264:Flowers / Q000378:metabolism / Q000502:physiology*; D007178:Inbreeding; D008853:Microscopy; D011058:Pollen / Q000502:physiology; D012098:Reproduction / Q000502:physiology; D012260:Ribonucleases / Q000378:metabolism / Q000502:physiology*; D032322:Solanum / Q000502:physiology*
D012260:Ribonucleases