Abstract Detail

Evolutionary Developmental Biology (Evo-Devo)

Patterson, Erin [1], Heeney, Michelle [2], Gallagher, Joseph [3], O'Connor, Devin [4], Cartwright, Amy [5], Bartlett, Madelaine [6].

The evolution and development of awns in the grass subfamily Pooideae.

Awns, projections from the outer floral organs or bracts of grass flowers, appear in almost every clade of grasses, with morphology varying from short and stubby to very long and twisted. They play complex roles for the plants that bear them, likely participating in grain loading as well as seed dispersal and establishment. Despite their ecological importance, awns remain relatively understudied: only a handful of genes involved in awn development have been identified, and the evolutionary history of awns remains unclear, particularly in the largest grass subfamily, the Pooideae. Here, we approach these open questions with a focus on the subfamily Pooideae and the model species Brachypodium distachyon. We take advantage of an existing B. distachyon mutant, awnless1 (awl1), which has delayed growth and defects in gynoecium development in addition to lacking awns. We examine the development of inflorescence meristems and gynoecia in WT and awl1 plants using scanning electron microscopy, and find evidence that a 90kb deletion is responsible for the awl1 mutation. We also perform ancestral state reconstruction for awn presence and insertion point, and find that the ancestor at the base of the Pooideae was likely awned, with multiple transitions between states occurring since then, suggesting a high degree of lability for the trait. Together, these findings further our understanding of the evolution and development of awns, and provide evidence supporting deeply conserved homology between leaves and lemmas. Morphological and ontological comparisons of leaves and lemmas have long suggested that leaves and lemmas are homologous organs, and this may explain the high degree of lability in awn presence and morphology, as conserved leaf blade pathways are redeployed in lemmas to produce and manipulate awns.

1 - University Of Massachusetts, Plant Biology Graduate Program, 204C French Hall, 230 Stockbridge Rd, Amherst, MA, 01003, United States
2 - University of Massachusetts, 611 N Pleasant St., Amherst, MA, 01003
3 - University Of Massachusetts, Biology Dept, 221 Morrill Science Center III, 611 North Pleasant St, Amherst, MA, 01003, United States
4 - Pairwise Plants, 807 E. Main Street, Durham, NC, 27701, USA
5 - DOE Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA, 94598, USA
6 - University Of Massachusetts Amherst, Biology Department, 611 North Pleasant St., 221 Morrill 3, Amherst, MA, 01003, United States

Keywords:
Brachypodium distachyon
Pooideae
awn.

Presentation Type: Oral Paper
Session: EVDV1, Evolutionary Developmental Biology (Evo-Devo)
Location: Virtual/Virtual
Date: Thursday, July 30th, 2020
Time: 1:30 PM
Number: EVDV1014
Abstract ID:617
Candidate for Awards:Katherine Esau Award