Abstract Detail

Insights into the diversity of plant sex chromosomes

Ashman, Tia-Lynn [1].

The secrets of plant sex determination as revealed by strawberries.

Sex chromosome evolution is thought to be a universal feature of separate-sexed organisms but our understanding of the process is heavily influenced by animal systems, the majority of which have ancient sex chromosomes. I will present research on North American species of wild strawberries (Fragaria, Rosaceae) demonstrating that plants not only provide valuable insight into the earliest stages of sex chromosome evolution from autosomes but also offer key parallels and unique differences to dynamics seen other stages in animal systems.  Using comparative approach across multiple species in the young Fragaria genus we have discovered at least four transitions from hermaphroditism to separate sexes, and multiple genetic avenues to loss of female function. Within the nascent (homomorphic) ZW sex determining system we revealed recombination heterogeneity between the sexes, as well as geographic patterns of variation in the chromosomal location of the sex determining region.  Using fine mapping and assembly of sequences unique to females across taxa, we characterized a female-specific “sex-determining cassette” that contains genes involved in fruit and pollen production, and when compared across taxa reflects the history of repeated translocation. The translocations can be ordered temporally due to the capture of adjacent sequence with each successive move. The accumulation of the “souvenir” sequence resulted in expansion of the hemizygous sex determining region over time lead to locking genes into linkage with sex. Terminal inverted repeats at the insertion borders suggest a means of movement.  This is the first plant sex determining region shown to be translocated, and it suggests a new mechanism (“move-lock-grow”) for expansion and diversification of incipient sex chromosomes. Thus, strawberry is providing unique insights into the evolutionary expansion and diversification of sex chromosomes in plants as well as separate-sexed organisms as a whole.  

1 - University of Pittsburgh, Biological Sciences, 4249 Fifth Avenue, Pittsburgh, PA, 15260, USA

sex chromosomes

Presentation Type: Symposium Presentation
Session: SY5, Insights into the diversity of plant sex chromosomes
Location: Virtual/Virtual
Date: Friday, July 31st, 2020
Time: 1:00 PM
Number: SY5007
Abstract ID:624
Candidate for Awards:None

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