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Title: CHROMOSOMAL LOCATION AND GENE PAUCITY IN THE MALE SPECIFIC REGION ON PAPAYA Y CHROMOSOME

Author
item YU, QINGYI
item HOU, SHAOBIN
item HOBZA, ROMAN
item FELTUS, F. ALEX
item WANG, XIUE
item JIN, WEIWEI
item SKELTON, RACHAEL
item BLAS, ANDREA
item LEMKE, CORNELIA
item SAW, JIMMY
item Moore, Paul
item ALAM, MAQSUDUL
item JIANG, JIMING

Submitted to: Molecular Genetics and Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2007
Publication Date: 7/5/2007
Citation: Yu, Q., Hou, S., Hobza, R., Feltus, F.A., Wang, X., Jing, W., Blas, A., Lemke,C., Saw, J.H., Moore, P.H., Alam, M., Jiang, J., Paterson, A.H., Vyskot, B., Ming, R. 2007. Chromosomal location and gene paucity of the male-specific region on papaya Y chromosome. Mol Genetics Genomics 278:177-185.

Interpretive Summary: Understanding the mechanisms of sex determination in fruit bearing crop plants can be crucial for maximizing fruit productivity and quality. Papaya, with one of the smallest chromosomal regions known to control sex, is a likely candidate for DNA sequencing to determine the genes involved in sex determination. A collaborative project among scientists of the Hawaii Agriculture Research Center, University of Hawaii, Czech Academy of Sciences, University of Georgia, University of Wisconsin, University of Illinois, and the USDA/ARS/PBARC was conducted to analyze the gene content of the papaya male specific region of its Y chromosome. A series of bacterial artificial chromosomes (BACs) were mapped to the MSY region and five of them were sequenced to reveal no functional gene within 715 kb sequences. Instead of genes, this region contained a high density of sequence insertions and duplication indicating evolutionary degeneration. In spite of having sequenced the largest amount of any plant sex determining region, additional work is required to identify a sex determination gene.

Technical Abstract: Sex chromosomes in flowering plants evolved recently and many of them remain homomorphic, including those in papaya. We investigated the chromosomal location of papaya’s small male specific region of the hermaphrodite Y (Yh) chromosome (MSY) and its genomic features. We conducted chromosome fluorescence in situ hybridization mapping of Yh-specific bacterial artificial chromosomes (BACs) and placed the MSY near the centromere of the papaya Y chromosome. Then we sequenced five MSY BACs to examine the genomic features of this specialized region, which resulted in the largest collection of contiguous genomic DNA sequences of a Y chromosome in flowering plants. Extreme gene paucity was observed in the papaya MSY with no functional gene identified in 715 kb MSY sequences. A high density of retroelements and local sequence duplications were detected in the MSY that is suppressed for recombination. Location of the papaya MSY near the centromere might have provided recombination suppression and fostered paucity of genes in the male specific region of the Y chromosome. Our findings provide critical information for deciphering the sex chromosomes in papaya and reference information for comparative studies other sex chromosomes in animals and plants.