Detection of Deleterious Genotypes in Multigenerational Studies. I. Disruptions in Individual Arabidopsis Actin Genes

Corresponding author: Richard B. Meagher, Department of Genetics, Life Sciences Bldg., University of Georgia, Athens, GA 30602-7223, meagher{at}bscr.uga.edu (E-mail).

Communicating editor: E. MEYEROWITZ

Plant actins are involved in numerous cytoskeletal processes effecting plant development, including cell division plane determination, cell elongation, and cell wall deposition. Arabidopsis thaliana has five ancient subclasses of actin with distinct patterns of spatial and temporal expression. To test their functional roles, we identified insertion mutants in three Arabidopsis actin genes, ACT2, ACT4, and ACT7, representing three subclasses. Adult plants homozygous for the act2-1, act4-1, and act7-1 mutant alleles appear to be robust, morphologically normal, and fully fertile. However, when grown as populations descended from a single heterozygous parent, all three mutant alleles were found at extremely low frequencies relative to the wild-type in the F₂ generation. Thus, all three mutant alleles appear to be deleterious. The act2-1 mutant allele was found at normal frequencies in the F₁, but at significantly lower frequencies than expected in the F₂ and F₃ generations. These data suggest that the homozygous act2-1/act2-1 mutant adult plants have a reduced fitness in the 2N sporophytic portion of the life cycle, consistent with the vegetative expression of ACT2. These data are interpreted in light of the extreme conservation of plant actin subclasses and genetic redundancy.

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