Abstract Detail

Development and Structure

Zumajo, Cecilia [1], Ambrose, Barbara [2].

Deciphering development of the seed coat in morphologically diverse seeds in members of Gnetales: Gnetum gnemon, Ephedra californica and Ephedra antisyphilitica.

The seed develops from an ovule or integumented megasporangium thus, the evolution of the integument is key in the evolution of seed plants. There are some key differences in the number of integuments present in seed plants as well as in the accessory structures that cover seeds in gymnosperms. Due to additional structures covering the nucellus, the ovules of Gnetales (Ephedra, Gnetum, Welwitschia) are strikingly different from all other extant gymnosperms. While in the genera Ephedra and Welwitschia two envelopes cover the nucellus, in the genus Gnetum are three envelopes that cover it. This study was approached from what is known in Arabidopsis, focusing on the expression patterns of homologs of four genes known to be key for the proper development of the integuments: AINTEGUMENTA (ANT), BELL1, (BEL1), KANADIs (KANs) and UNICORN (UCN). We used histology to describe the morphoanatomical development from ovules to seeds, in Gnetum gnemon. We carried out spatiotemporal expression analyses in Gnetum gnemon. The homologs studied here, are found expressed in the nucellus, revealing major differences in seed plants. No expression of the homologs studied was detected in the outer envelopes. With the aim to gain a better understanding of the putative genes that may be involved in envelope formation in Gnetales, we performed transcriptome analyses in Ephedra californica and Ephedra antisyphilitica which envelopes become dry and fleshy, respectively, as the seed matures. Our findings suggest that the integument genes were most likely recruited from the sporangium development network and became restricted to the integument of angiosperm ovules. Altogether our results provide evidence supporting the synangial hypothesis for the origin of the integument.

1 - New York Botanic Garden, 2900 Southern Blvd. Bronx, New York, NY, 10458, United States
2 - The New York Botanical Garden, 2900 Southern Blvd, Bronx, NY, 10458, United States

Keywords:
ovules
evo-devo
synangial hypothesis
morpho-anatomy
seed anatomy
development.

Presentation Type: Oral Paper
Session: DS2, Development and Structure II
Location: /
Date: Wednesday, July 21st, 2021
Time: 1:30 PM(EDT)
Number: DS2014
Abstract ID:128
Candidate for Awards:None