| Abstract Detail
Evolutionary Developmental Biology (Evo-Devo) Lindqvist, Charlotte [1], Laakkonen, Liisa [2], Albert, Victor A. [1]. Polyglutamine variation in the flowering time protein FCA contributes to the Hawaiian mint morphological radiation. A controversial topic in evolutionary developmental biology is whether morphological diversification in natural populations can be driven by expansions and contractions of amino acid repeats in proteins. To promote adaptation, selection on protein length variation must overcome deleterious effects of multiple correlated traits (pleiotropy). Thus far, systems that demonstrate this capacity include only ancient or artificial morphological diversifications. The Hawaiian Islands, with their linear geological sequence, present a unique environment to study recent, natural radiations. We have focused our research on the Hawaiian endemic mints (Lamiaceae), a large and diverse lineage with paradoxically low genetic variation, in order to test whether a direct relationship between coding-sequence repeat diversity and morphological change can be observed in an actively evolving system. Here we show that in the Hawaiian mints, extensive polyglutamine (CAG codon repeat) polymorphism within a homolog of the pleiotropic flowering time protein and abscisic acid receptor FCA tracks the natural environmental cline of the island chain across a period of 5 million years. Polyglutamine expansions are more frequent in colonists of recently-formed, nutrient-rich islands than in their forebears on older, nutrient-poor islands. Values for several quantitative morphological variables related to reproductive investment, known from Arabidopsis fca mutant studies, positively correlate with increasing glutamine tract length. Together with protein modeling of FCA, which suggests that longer polyglutamine tracts could induce suboptimally mobile functional domains, we interpret CAG expansions as slightly deleterious alleles that became fixed in founder populations. The Hawaiian mint radiation, paradoxically, appears to have “taken advantage” of developmental pleiotropy by way of natural selection on slightly deleterious genetic variation. Multiple, correlated phenotypic differences appear to have been generated as a by-product of the natural tendency of CAG codon repeats to elongate and thereafter contract under selection pressure, here, competition for resources.
Log in to add this item to your schedule
Related Links:
Lindqvist C, et al. 2006. An expressed sequence tag (EST) library from developing fruits of an Hawaiian endemic mint (Stenogyne rugosa, Lamiaceae): characterization and microsatellite markers. BMC Plant Biology, 6:16.
-- Plant Genome Network (Stenogyne ESTs and unigenes)
1 - University of Oslo, Natural History Museum, P.O. Box 1172 Blindern, Oslo, NO-0318, Norway
2 - University of Helsinki, Institute of Biotechnology, Biocenter 3 (Viikinkaari 1), PB 65, Helsinki, FIN-00014, Finland
Keywords:
evo-devo
Hawaiian Islands
Lamiaceae
EST-SSR
flowering time
adaptive radiation
FCA
pleiotropy
polyglutamine
CAG repeat
reproductive investment.
Presentation Type: Oral Paper:Papers for Topics
Session: CP46
Location: Astoria Room/Hilton
Date: Wednesday, July 11th, 2007
Time: 9:30 AM
Number: CP46005
Abstract ID:1057 |
