One-sentence summary: Mutant analysis and transgenic experiments in the model plant 19 monkeyflower (Mimulus) identify a tetratricopeptide repeat protein required for chromoplast 20 development and carotenoid biosynthesis.
Summary
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.
Pollen morphology of 11 species of Murraya and Micromelum (Clauseneae: Rutaceae) was investigated using scanning electron microscopy (SEM) and palynological characters including pollen size, aperture number and exine ornamentation were evaluated. The results indicate that species in M. sect. Bergera and sect. Murraya have very distinct pollen morphology. Species in section Bergera have rugulate to foveolate exine, whereas the tectum in section Murraya is crossstriate. This supports the redefinition of the genus Murraya, retaining only the species of section Murraya, while M. sect. Bergera is better treated as a separate genus. From the palynological point of view, it is suggested that Bergera and Murraya s.s. are not closely related, with the latter being more close to Micromelum and Merrillia, a result in accordance with phytochemical, chromosomal and molecular evidence, thus supporting the reinstatement of the generic name Bergera L.
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