Abstract Detail

Colloquium: Speaking of Food: connecting basic and applied science

Kellogg, Elizabeth [1], Camara, Paulo [2], Rudall, Paula [3], Ladd, Philip [4], Malcomber, Simon [5], Whipple, Clinton [6], Doust, Andrew [7].

Early inflorescence development in the grasses (Poaceae).

Yield in cereal crops reflects both seed number and seed weight, the former controlled by the number of floral meristems and the latter by carbohydrate transport to the grain. Ultimately both are products of inflorescence architecture, including the number of branches and their arrangement, produced by the shoot apical meristem. In most grasses, including many of the cereals, primary inflorescence branches are produced in a spiral. This represents a shift from vegetative phyllotaxis, in which leaves are produced in a distichous pattern with the primordia separated from each other by an angle of 180^o. The morphology and developmental genetics of this shift have been studied extensively in maize and rice. However, in wheat, Brachypodium, and oats, all in the grass subfamily Pooideae, the change in phyllotaxis does not occur; primary inflorescence branches are distichous. It is unknown whether the origin of the distichous inflorescence correlated with a massive change in genome size and a reduction in chromosome number in the common ancestor of the tribes Triticeae and Poeae, or with the colonization of cool temperate habitats in the common ancestor of the subfamily, or whether distichy appeared multiple times independently. In this study, we show that Brachyelytrum, the genus sister to all other Pooideae, has spiral phyllotaxis in the inflorescence, but we infer that in the remaining 3000+ species of Pooideae, the phyllotaxis is two-ranked. The origin of two-ranked phyllotaxis thus correlates with neither the genomic change nor the habitat change. The two-ranked inflorescences are not perfectly symmetrical, and have a clear “front” and “back;” this developmental axis has never been described in the literature and it is unclear what establishes its polarity. Two-ranked inflorescences also appear in a few grass outgroups and sporadically elsewhere in the family, but unlike in Pooideae do not generally correlate with a major radiation of species. After production of branches, the inflorescence meristem may be converted to a spikelet meristem or may simply abort; this developmental decision appears to be independent of the branching pattern.

Broader Impacts:

1 - University of Missouri - St. Louis, Department of Biology, One University Boulevard, St. Louis, MO, 63121-4499, USA, 314/516-6217
2 - University of Brasilia, Department of Botany, Brasilia, DF, Brazil
3 - Jodrell Laboratory, Royal Botanic Gardens KEW, Richmond, N/A, TW9 3DS, United Kingdom
4 - Murdoch University, School of Veterinary and Life Sciences, Perth, WA, Australia
5 - National Science Foundation, 4201 Wilson Blvd, Arlington, VA, 22230, USA
6 - Brigham Young University, Biology, 679 WIDB, Provo, UT, 84602, USA
7 - Oklahoma State University, Botany, Physical Sciences Room 301, Stillwater, OK, 74078, USA

Keywords:
phyllotaxis
cereal crop
phylogeny
branching
shoot apical meristem.

Presentation Type: Symposium or Colloquium Presentation
Session: C7
Location: Grand Ballroom A/Riverside Hilton
Date: Tuesday, July 30th, 2013
Time: 3:15 PM
Number: C7006
Abstract ID:551
Candidate for Awards:None