A dominant-negative actin mutation alters corolla tube width and pollinator visitation in Mimulus lewisii.
A third of all angiosperm species produce flowers with petals fused into a corolla tube. The various elaborations of corolla tube attributes, such as length, width and curvature, have enabled plants to exploit many specialized pollinator groups. These elaborations often differ dramatically among closely related species, contributing to pollinator shift and pollinator-mediated reproductive isolation and speciation. However, very little is known about the genetic and developmental control of these corolla tube attributes. Here we report the characterization of a semi-dominant mutant in the monkeyflower species Mimulus lewisii, with a substantial decrease in corolla tube width but no change in tube length. This morphological alteration leads to a ˜ 70% decrease in bumblebee visitation rate for the homozygous mutant compared to the wild-type. Through bulk segregant analysis and transgenic experiment, we show that the mutant phenotype is caused by a dominant-negative mutation in an actin gene. This mutation decreases epidermal cell width but not length, and probably also reduces the number of lateral cell divisions. These results suggest a surprising potential role for a 'housekeeping' gene in fine-tuning the development of an ecologically important floral trait.
Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA.
Baoqing
B
Ding
Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA.|Faculty of Forestry, Southwest Forestry University, Kunming, 650224, China.
Fengjuan
F
Mou
Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, 100700, China.
Wei
W
Sun
Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, 100700, China.
Shilin
S
Chen
Department of Biology, University of Washington, Seattle, WA, 98195, USA.
Foen
F
Peng
Department of Biology, University of Washington, Seattle, WA, 98195, USA.
Harvey D
HD
Bradshaw
Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA.|Institute for Systems Genomics, University of Connecticut, Storrs, CT, 06269, USA.
Yao-Wu
YW
Yuan
D000199:Actins / Q000235:genetics*; D000483:Alleles; D000818:Animals; D001516:Bees / Q000502:physiology*; D048430:Cell Shape; D048429:Cell Size; D035264:Flowers / Q000033:anatomy & histology* / Q000166:cytology; D005799:Genes, Dominant; D032241:Mimulus / Q000166:cytology / Q000235:genetics* / Q000502:physiology*; D009154:Mutation / Q000235:genetics*; D009929:Organ Size; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics; D030821:Plants, Genetically Modified; D054817:Pollination / Q000502:physiology*
D000199:Actins; D010940:Plant Proteins

Mimulus
; Pollination; actin; corolla tube; dominant-negative