Submitted to: Microbial Pathogensis and Host Response: Cold Spring Harbor Laboratory
Publication Type: Proceedings
Publication Acceptance Date: 1/5/2007
Publication Date: 3/1/2007
Citation: Yu, Q., Hou, S., Feltus, A., Moore, R.C., Moore, P.H., Alam, M., Jiang, J., Paterson, A., Ming, R. 2007. Recent Origin of the Papaya Sex Chromosomes. Cold Spring Harbor Laboratory.
Interpretive Summary: not applicable
Technical Abstract: Sex chromosomes in flowering plants, in contrast to those in animals, evolved relatively recently and only a few are heteromorphic. The sex chromosomes of papaya appear at the cytological level to be homomorphic but, at the molecular level, we are finding that the papaya Y chromosome shows features of incipient sex chromosome evolution. To survey the state of the hermaphrodite Y (Yh) chromosome differentiation, we sequenced two pairs of X and Yh specific bacterial artificial chromosomes (BACs) and conducted functional analysis on two X BACs and seven Yh BACs. Sequence comparison between the two paired X and Yh BACs revealed three inversion events on the MSY. Aligning the paired BAC sequences showed that one of the Yh BACs had expanded by 9.6% and the other Y BAC had expanded by 35.2%. One gene on the Yh chromosome might have been lost by deletion, while its corresponding gene on the X chromosome is still functional. Analysis of sequence divergence between five X and Yh gene pairs indicates that they are functionally constrained, which is a characteristic of young sex chromosomes. Our estimate of the age of divergence between X-Y gene pairs ranges from 1.3-2.8 million years ago, supporting a recent origin of the primitive sex chromosomes in papaya.