Evolutionary Developmental Biology (Evo-Devo)
Whipple, Clinton , Bybee, Seth , Jackson, David .
Evolution of a bract suppression mechanism in the grass family.
Leaf growth is often suppressed after the transition from vegetative to reproductive growth. Inflorescence leaves are called bracts, and bract suppression has evolved several times in the angiosperms. We have begun a genetic characterization of the bract suppression pathway in the grass family. Several maize mutants with de-repressed bract growth, known as tasselsheath (tsh), have been isolated. The genes responsible for two of these mutants, tsh1 and tsh4, have been cloned. Interestingly, the Tsh1 and Tsh4 orthologs in Arabidopsis do not have a bract suppression function and it appears that distinct bract suppression mechanisms have evolved in the Brassicaceae and the Poaceae. The genetic mechanism of bract suppression is conserved in distantly related grasses as the barley third outer glume (trd) and the rice neck leaf1 (nl1) mutants both have a similar bract growth phenotype and are caused by mutations Tsh1 orthologs. We are currently investigating the evolution of NL1/Tsh1/TRD (NTT) genes in grasses and bracteate outgroups. Our phylogenetic analysis indicates that there are three paralogous clades of NTT genes in the grasses created by sequential duplication events. Interestingly, the lineage containing the bract suppresion genes Tsh1, NL1 and TRD arose before the evolution of bract suppression at the base of the grass family. When expressed in lateral organs of transgenic Arabidopsis, both HAN and Tsh1 are capable of suppressing outgrowth, suggesting that grass bract suppression involved evolution of a novel expression domain in the NTT lineage. We are testing for this by examining the expression domains of NTT and related genes in grasses and outgroups.
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1 - Brigham Young University, Biology, 401 Widb, Provo, UT, 84604, USA
2 - Cold Spring Harbor Laboratory, 1 Bungtown Rd., Cold Spring Harbor, NY, 11724, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Lindell D/Chase Park Plaza
Date: Wednesday, July 13th, 2011
Time: 8:15 AM