Abstract
Multigene families encoding class XI myosins are conserved in higher plants, however, little information is available on specific functions of these ubiquitous molecular motors. We isolated gene knockout mutants for all 13 class XI myosins present in Arabidopsis (Arabidopsis thaliana) genome. Inactivation of 11 myosin genes resulted in no discernible phenotypes under the normal growth conditions. In contrast, the knockouts of the remaining two myosin genes, XI-2 (formerly MYA2) and XI-K, exhibited similar defects in root hair elongation suggesting that the myosin-driven motility plays a significant role in a polar tip growth. Strikingly, inactivation of each of these myosins also reduced trafficking of Golgi stacks, peroxisomes, and mitochondria in root hairs and in leaf epidermal cells. These results indicate that myosins XI-K and XI-2 play major and overlapping roles in the cell dynamics in Arabidopsis and highlight the redundant nature of myosin function in plants.
Highlights
Multigene families encoding class XI myosins are conserved in higher plants, little information is available on specific functions of these ubiquitous molecular motors
Sixteen homozygous lines in which each of the 13 class XI myosin genes of Arabidopsis was inactivated by T-DNA insertion were obtained and the exact localization of the insert was determined by sequencing (Fig. 1A; data not shown)
Two independent lines for myosin XI-K and three for myosin XI-2 genes were selected for further experiments to ensure that the observed phenotypes were due to the T-DNA insertion in the corresponding locus rather than to secondary site mutations
Summary
Multigene families encoding class XI myosins are conserved in higher plants, little information is available on specific functions of these ubiquitous molecular motors. Inactivation of each of these myosins reduced trafficking of Golgi stacks, peroxisomes, and mitochondria in root hairs and in leaf epidermal cells These results indicate that myosins XI-K and XI-2 play major and overlapping roles in the cell dynamics in Arabidopsis and highlight the redundant nature of myosin function in plants. Inactivation of the genes encoding the most closely related paralogs of myosins XI-K and XI-2 and myosins XI-1 (MYA1) and XI-B, respectively, did not impair root hair growth or organelle trafficking. These results indicate that evolution of myosins in plants combines opposing tendencies of functional specialization and functional redundancy
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