GAI homologues in the Hawaiian silversword alliance (Asteraceae-Madiinae): molecular evolution of growth regulators in a rapidly diversifying plant lineage

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
David L. Remington, Associate Professor (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site:

Abstract: Accelerated evolution of regulatory genes has been proposed as an explanation for decoupled rates of morphological and molecular evolution. The Hawaiian silversword alliance (Asteraceae-Madiinae) has evolved drastic differences in growth form, including rosette plants, cushion plants, shrubs, and trees, since its origin ~6 MYA. We have isolated genes in the DELLA subfamily of putative growth regulators from 13 taxa of Hawaiian and North American Madiinae. The Hawaiian taxa contain two copies of DaGAI that form separate clades within the Madiinae, consistent with an allotetraploid origin for the silversword alliance. DaGAI retains conserved features that have previously been identified in DELLA genes. Selective constraint in the Hawaiian DaGAI copies remains strong in spite of rapid growth form divergence in the silversword alliance, although the constraint was somewhat relaxed in the Hawaiian copies relative to the North American lineages. We failed to detect evidence for positive selection on individual codons. Notably, selective constraint remained especially strong in the gibberellin-responsive DELLA region for which the gene subfamily is named, which is truncated or deleted in all identified dwarf mutants in GAI homologues in different angiosperm species. In contrast with the coding region, however, ~900 bp of the upstream flanking region shows variable rates and patterns of evolution, which might reflect positive selection on regulatory regions.

Additional Information

Molecular Biology and Evolution 19(9):1563-1574
Language: English
Date: 2002
Madiinae, silversword alliance, GAI adaptive radiation, selection, regulatory genes

Email this document to