Abstract
The genus Phoenix includes the fruit producing date palm tree among 14 species that are all dioecious. Females produce the fruit that are high in sugar content and used in multiple countries ranging from North Africa to South Asia, especially from the Phoenix dactylifera, Phoenix sylvestris, and Phoenix canariensis species. While females produce the fruit, understanding of the genetic basis of sex control only began recently. Through genus-wide sequencing of males and females we recently identified three genes that are conserved in all males and absent in all females of the genus and confirmed an XY sex chromosome system. While our previous study focused on conservation of male-specific sequences at the genus-level, it would be of interest to better understand the spread of male-specific sequences away from the core conserved male genes on the Y chromosome during speciation. To this end, we enumerated male-specific 16 bp sequences using three male/female pairs from the western subpopulation of date palm and documented the density of these sequences in contigs of a phased date palm genome assembly. Here we show that male specific sequences in the date palm Y chromosome have likely spread in defined events that appear as blocks of varying density with significant changes in density between them. Collinearity of genes in these blocks with oil palm shows high synteny with chromosome 10 between megabase 15 and 23 and reveals that large sections of the date palm Y chromosome have maintained the ancestral structure even as recombination has stopped between X and Y.
Highlights
Date palm (Phoenix dactylifera) is one of the most ancient cultivated trees that have adapted to withstand extreme environmental conditions prevalent in arid and semi-arid regions
Biotechnological interest in the sex determination system of date palm arose because males do not produce fruit and only a single male tree is needed to pollinate multiple female trees
The observation that seed propagated date palm produce equal numbers of male and female progeny suggested that sex determination was genetic and not environmental
Summary
Date palm (Phoenix dactylifera) is one of the most ancient cultivated trees that have adapted to withstand extreme environmental conditions prevalent in arid and semi-arid regions. Biotechnological interest in the sex determination system of date palm arose because males do not produce fruit and only a single male tree is needed to pollinate multiple female trees. The observation that seed propagated date palm produce equal numbers of male and female progeny suggested that sex determination was genetic and not environmental. Almost 60 years later, Siljak-Yakovlev and collaborators used a probe to identify heterochromatin in chromosome spreads and determined that females had a pair of similar heterochromatin spots while the analogous pair in males was heteromorphic, suggesting the presence of an XY sexdetermination system in date palm (Siljak-Yakovlev et al, 1996)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
