Myosins XI-K, XI-1, and XI-2 are required for development of pavement cells, trichomes, and stigmatic papillae in Arabidopsis

Eve-Ly Ojangu,Erkki Truve,Heiti Paves,Krista Tanner,Kristel Järve,Carola L Holweg,Pille Pata

doi:10.1186/1471-2229-12-81

Abstract

BackgroundThe positioning and dynamics of vesicles and organelles, and thus the growth of plant cells, is mediated by the acto-myosin system. In Arabidopsis there are 13 class XI myosins which mediate vesicle and organelle transport in different cell types. So far the involvement of five class XI myosins in cell expansion during the shoot and root development has been shown, three of which, XI-1, XI-2, and XI-K, are essential for organelle transport.ResultsSimultaneous depletion of Arabidopsis class XI myosins XI-K, XI-1, and XI-2 in double and triple mutant plants affected the growth of several types of epidermal cells. The size and shape of trichomes, leaf pavement cells and the elongation of the stigmatic papillae of double and triple mutant plants were affected to different extent. Reduced cell size led to significant size reduction of shoot organs in the case of triple mutant, affecting bolt formation, flowering time and fertility. Phenotype analysis revealed that the reduced fertility of triple mutant plants was caused by delayed or insufficient development of pistils.ConclusionsWe conclude that the class XI myosins XI-K, XI-1 and XI-2 have partially redundant roles in the growth of shoot epidermis. Myosin XI-K plays more important role whereas myosins XI-1 and XI-2 have minor roles in the determination of size and shape of epidermal cells, because the absence of these two myosins is compensated by XI-K. Co-operation between myosins XI-K and XI-2 appears to play an important role in these processes.

Highlights

The positioning and dynamics of vesicles and organelles, and the growth of plant cells, is mediated by the acto-myosin system
When primers downstream of the TDNA insertion site were used for RT-PCR, the respective myosin transcript was absent in xi-2, present in xi-1 (Figure 1) and present in xi-k mutants
In xi-1 mutant, the T-DNA is inserted into the coding region; we assumed that no functional XI-1 protein can be produced in this single mutant as well as in respective double and triple mutant plants

Summary

Introduction

The positioning and dynamics of vesicles and organelles, and the growth of plant cells, is mediated by the acto-myosin system. In Arabidopsis there are 13 class XI myosins which mediate vesicle and organelle transport in different cell types. The involvement of five class XI myosins in cell expansion during the shoot and root development has been shown, three of which, XI-1, XI-2, and XI-K, are essential for organelle transport. Studies have shown that cytoskeletal dynamics, vesicle transport, small GTPase signaling and endoreduplication all play a role in the development of the specialized shapes of different epidermal cell types. A novel role in regulation of the actin cytoskeleton and ER dynamics has been shown for class XI myosins [22,23].

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