22 May 2019
The separation of the sexes in date palms
Published online 12 October 2018
Two genes are found to influence male fertility while another represses female flower organs.
Sex determination systems in plants are much more varied than in animals. Until now, it wasn’t known how sex was determined in date palms.
A research team in Qatar has identified four candidate genes in male date palms that give them male attributes. Of the four, they identified the functions of three as likely being sex-determining genes. The findings provide new insights into how genes influence sex determination in plants.
Male date palm trees don’t bear fruits, but female trees do. It takes about five to eight years for female seedlings to bear fruits, which is when they become distinguishable from male trees.
Researchers found a region on the male date palm genome where two genes appear to have been deleted from the female date palms and relocated onto the sex-determining chromosome of males. This translocation probably happened at a time in history when date palms were hermaphrodites, bearing female and male flowers on the same plants. This translocation was the first step toward the development of sexes in separate trees. When female and male flowers evolved on separate trees, the two genes related to male flower development and its function were lost in the female plants. Those genes are now found only in male date palms.
The study also identified a third gene that could be suppressing the development of the female flower organ in males.
Since only one male is needed to fertilize approximately 50 to 100 female trees, the findings are expected to help improve breeding and increase date palm yields by being able to screen out males while the plants are still young, explains corresponding author Joel Malek from Weill Cornell Medicine-Qatar in Doha.
Next, the team plans to identify genes that control date fruit texture, sweetness and fruit length. They also hope to find genetic markers that will help select date palms that are resilient to stresses such as climate change and diseases.
Torres, M. F. et al. Genus-wide sequencing supports a two-locus model for sex-determination in Phoenix. Nat. Commun. 9, 3969 (2018).