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1000
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Abstract/Summary
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KINETOCHORE NULL2 (KNL2) plays key role in the recognition of centromeres and new CENH3 deposition. To gain insight into the origin and diversification of the KNL2 gene, we reconstructed its evolutionary history in the plant kingdom. Our results indicate that the KNL2 gene in plants underwent three independent ancient duplications in ferns, grasses and eudicots. Additionally, we demonstrated that previously unclassified KNL2 genes could be divided into two clades alphaKNL2 and betaKNL2 in eudicots and gammaKNL2 and deltaKNL2 in grasses, respectively. KNL2s of all clades encode the conserved SANTA domain, but only the alphaKNL2 and gammaKNL2 groups additionally encode the CENPC-k motif. In the more numerous eudicot sequences, signatures of positive selection were found in both alphaKNL2 and betaKNL2 clades, suggesting recent or ongoing adaptation. The confirmed centromeric localization of betaKNL2 and mutant analysis suggests that it participates in loading of new CENH3, similarly to alphaKNL2. A high rate of seed abortion was found in heterozygous betaKNL2 plants and the germinated homozygous mutants did not develop beyond the seedling stage. Taken together, our study provides a new understanding of the evolutionary diversification of the plant kinetochore assembly gene KNL2, and suggests that the plant-specific duplicated KNL2 genes are involved in centromere and/or kinetochore assembly for preserving genome stability.
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