Abstract Detail

Comparative Genomics/Transcriptomics

Chae, Taylor [1], Harkess, Alex [2], Moore, Rich [3].

Differential gene expression linked to a reversion from dioecy to gynodioecy in Carica papaya .

Dioecy is thought to have evolved from hermaphroditism and was established in flowering plants through two types of mutations, a male sterility mutation and a female sterility mutation. However, reversions to gynodioecious populations of females and hermaphrodites can occur in some plants, including the tropical fruit crop, Carica papaya (papaya). Papaya has young sex chromosomes, with homogametic females (XX), heterogametic males (XY) and hermaphrodites with a slightly different Y chromosome (XY^h). Approximately 4,000 years ago, the male Y chromosome diverged, resulting in the hermaphroditic Y^h chromosome. The Y and Y^h chromosomes are only 0.4% divergent in nucleotide sequence, and gene content and exon structure are conserved across both chromosomes. However, major morphological differences exist in males and hermaphrodites. Specifically, the male flowers contain a nonfunctional pistil that is aborted early in development called the pistillode while hermaphroditic flowers contain a functional and fully developed pistil. I hypothesize that these differences between males and hermaphrodites as well as the cause of the reverse sexual transition in papaya is due to differentially expressed Y and Y^h-linked genes. Specifically, I expect a masculinization gene(s) in the sex determining region that suppresses carpel formation to be on in males but off in females during development. RNA extraction and RNA-seq of early and late developmental buds of males, females and hermaphrodites was completed and all samples were sequenced. HISAT2, StringTie and DESeq2 were used to analyze transcript abundance and identify differentially expressed genes. Continuing work includes identifying these differentially expressed genes and comparing them to homologs in other flowering plants. Studying differences in expression could lead to the identification of sex-determining genes in the sex-determining regions of the Y and Y^h chromosomes. This could eventually allow for the development of a true-breeding papaya plant that only produces hermaphrodites.

1 - Miami University, Botany Dept., 700 E. High Street, Pearson Hall, Oxford, OH, 45056, United States
2 - Donald Danforth Plant Center, St.Louis
3 - Miami University, Biology, 316 Pearson, Oxford, OH, 45056, United States

Keywords:
Quantitative Genetics
Evolution
Differential Expression Analysis.

Presentation Type: Poster
Session: P, Comparative Genomics and Transcriptomics
Location: Grand Ballroom - Exhibit Hall/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PGT009
Abstract ID:431
Candidate for Awards:Genetics Section Poster Award