Abstract Detail

Evolutionary Developmental Biology (Evo-Devo)

Skema, Cynthia [1], Ambrose, Barbara [2], Tate, Jennifer [1].

How to build two houses from one: Morphological and genetic study of dioecious floral development in Plagianthus (Malvaceae).

Unisexual flowers have evolved repeatedly throughout angiosperms, yet little is understood of the diversity of how these many, independent lineages have evolved to separate their sexes, with in-depth studies mostly limited to monoecious/dioecious crop plants and a few classic examples (e.g., Silene, Rumex). Here we probe the diversity of dioecy with a study aimed at characterizing the morphology, anatomy and genetics underlying floral development in Plagianthus (Malvaceae), a genus containing two dioecious species that are each endemic to New Zealand. Our study of floral development in both species showed that dioecy in the genus occurs late, with nearly complete development of the androecia in females and the gynoecia (including ovules) in males. SEM and histological studies enabled us to pinpoint the timing of abortion of these parts. To study early floral developmental genetics in Plagianthus, we investigated MADS-box gene expression, concentrating on the androecium and gynoecium, via in situ hybridizations of all five B- and C-class genes. Probe sequences were derived from twelve copies of these genes (two AP3, two TM6, three PI, two AG, and three PLE) isolated from Plagianthus buds. We hypothesized that expression would correspond to the classic ABC model in both sexes given how late dioecy is expressed in Plagianthus, i.e., floral organ initiation in the androecial and gynoecial whorls should be identical between the sexes in Plagianthus because both whorls are present (albeit one is infertile) in mature Plagianthus flowers of either sex. A comparison of male versus female gene expression patterns from in situs in the floral organ initiation stage confirmed our hypothesis. Characterization of later floral gene expression in Plagianthus is in progress through the analysis of floral transcriptome sequences, as a means to search for differential gene expression between the sexes and to find (potentially novel) candidate genes for sex determination. This dataset consists of 186 million reads (100 bp, paired end) of Illumina data sequenced from the floral transcriptomes of i) Plagianthus males, ii) Plagianthus females , and iii) Hoheria, the nearest hermaphroditic relative to Plagianthus, with each transcriptome consisting of two separately tagged, cDNA libraries prepared from mid- and late-floral developmental stages.

Broader Impacts:

1 - Massey University, Private Bag 11222, Palmerston North, N/A, 4442, New Zealand
2 - The New York Botanical Garden, IMBS, 200th St. And Southern Blvd., Bronx, NY, 10458, USA

Keywords:
dioecy
Plagianthus
ribbonwood
MADS-box
floral transcriptomics
floral evolution.

Presentation Type: Oral Paper:Papers for Topics
Session: 42
Location: Jasperwood/Riverside Hilton
Date: Wednesday, July 31st, 2013
Time: 10:15 AM
Number: 42001
Abstract ID:241
Candidate for Awards:None