Dating a hermaphrodite
A physical map of the papaya MSY was constructed from the AU9 male BAC library, using probes from BACs in the HSY physical map (Gschwend et al. Candidate BACs were confirmed by a combination of PCR and BAC end sequencing, and gaps in the physical map were filled using chromosome walking (see Methods).The MSY physical map consists of a minimum tiling path of 99 BACs (Supplemental Fig.Sequences from papaya males from natural populations therefore offer the opportunity to identify the gene or genes responsible for the gender difference.The papaya HSY has been sequenced previously, using BAC libraries from the gynodioecious cultivar “Sun Up,” a popular commercial transgenic cultivar from Hawaii (Wang et al. To study the MSY, the dioecious “AU9” cultivar from the USDA germplasm repository in Hilo was selected, because it was one of the few dioecious accessions available with a desirable fruit appearance.Intersex is an umbrella term used to describe a wide range of natural bodily variations.
The sex chromosomes in other organisms, such as mammals, are ancient (Veyrunes et al. Moreover, sequencing multiple individuals of both males and hermaphrodites is necessary, because the origin or origins of hermaphrodites are unknown, and the AU9 MSY might not be closely related to the ancestor of the HSY, as we indeed show to be the case.
The identification of the ancestral MSY3 haplotype will expedite investigation of the mutation leading to the domestication of the hermaphrodite Y Gender in papaya is genetically controlled by a sex-linked region that behaves like an XY sex chromosome, and maleness versus hermaphroditism is controlled by slightly different sex-specific Y chromosome regions, Y (HSY) in hermaphrodites and Y (MSY) in males. The corresponding region of the X is only 3.5 Mb, and both the Y and Y) is inviable, and the embryos abort 25–50 d after pollination, suggesting that the Y chromosome types are similar and that both are missing an essential gene that is functional in the X.
Both the HSY and MSY are ∼8.1 Mb (∼15% of the largest papaya chromosome, Chromosome 1), and recombination with the X is suppressed, so that hermaphrodite- and male-specific regions can be defined (Liu et al. Wild papaya populations are dioecious, with one-half male and one-half female plants, whereas cultivated papaya is predominantly gynodioecious, with two-thirds hermaphrodite and one-third female plants, though dioecious varieties do exist.
chromosome (HSY) and its X chromosome counterpart were sequenced and analyzed previously.
We now report the sequence of the entire male-specific region of the Y (MSY).