In papers published online in advance this week in PNAS, scientists discuss sex determination in the papaya and highlight genetic factors behind the progression of prion disease in mice.
An international team led by investigators at the University of Illinois at Urbana-Champaign reports having examined early sex chromosome evolution in papaya by sequencing the hermaphrodite-specific region of the Yhchromosome and its X counterpart. The team found that the former differs from the latter "by two large-scale inversions, the first of which likely caused the recombination suppression between the X and Yh chromosomes, followed by numerous additional chromosomal rearrangements," it writes.
Another group led by researchers at Urbana-Champaign reports having "compared the recently evolved papaya sex chromosomes with a homologous autosome of a close relative, the monoecious Vasconcellea monoica, to infer changes since recombination stopped between the papaya sex chromosomes." Overall, the team says, "given that the V. monoica genome is 41 percent larger than that of papaya," their findings suggest "considerable expansion of the papaya X."
Elsewhere in this week's PNAS Early Edition, scientists at the UK's Medical Research Council and at University College London show that "overexpression of the Hspa13 (Stch) gene reduces prion disease incubation time in mice." Meantime, investigators at the Scripps Research Institute in La Jolla, Calif., and at the University of California, San Diego, show that "disruption of copper homeostasis due to a mutation of Atp7a delays the onset of prion disease" in mice.