The type II Arabidopsis formin14 interacts with microtubules and microfilaments to regulate cell division.

Yanhua Li,Yuan Shen,Chenchun Zhong,Ming Yuan,Haiyun Ren,Lei Zhu,Chao Cai

doi:10.1105/tpc.110.075507

Yanhua Li, Yuan Shen + Show 5 more

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https://doi.org/10.1105/tpc.110.075507

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Abstract

Formins have long been known to regulate microfilaments but have also recently been shown to associate with microtubules. In this study, Arabidopsis thaliana FORMIN14 (AFH14), a type II formin, was found to regulate both microtubule and microfilament arrays. AFH14 expressed in BY-2 cells was shown to decorate preprophase bands, spindles, and phragmoplasts and to induce coalignment of microtubules with microfilaments. These effects perturbed the process of cell division. Localization of AFH14 to microtubule-based structures was confirmed in Arabidopsis suspension cells. Knockdown of AFH14 in mitotic cells altered interactions between microtubules and microfilaments, resulting in the formation of an abnormal mitotic apparatus. In Arabidopsis afh14 T-DNA insertion mutants, microtubule arrays displayed abnormalities during the meiosis-associated process of microspore formation, which corresponded to altered phenotypes during tetrad formation. In vitro biochemical experiments showed that AFH14 bound directly to either microtubules or microfilaments and that the FH2 domain was essential for cytoskeleton binding and bundling. However, in the presence of both microtubules and microfilaments, AFH14 promoted interactions between microtubules and microfilaments. These results demonstrate that AFH14 is a unique plant formin that functions as a linking protein between microtubules and microfilaments and thus plays important roles in the process of plant cell division.

Highlights

Microtubules and microfilaments represent two major plant cell cytoskeletal networks, both of which play important roles in many aspects of the fundamental processes of plant cell growth and development, including cell division, cell expansion, intracellular organization, and cell motility
Because the FH1FH2 region is highly conserved across formin family members, we expected that the polyclonal antibodies were likely to recognize other formins
All formins identified to date in plant cells have been characterized as microfilament regulators (Blanchoin and Staiger, 2008), with the exception of the most recently reported formin, AFH4, which can bind microtubules in addition to microfilaments (Deeks et al, 2010)

Summary

Introduction

Microtubules and microfilaments represent two major plant cell cytoskeletal networks, both of which play important roles in many aspects of the fundamental processes of plant cell growth and development, including cell division, cell expansion, intracellular organization, and cell motility. There is no question that microtubules and microfilaments constitute separate cytoskeletal systems and fulfill distinct functions. A growing body of evidence suggests that functional interactions between microtubules and microfilaments are important for specific cellular processes. During cytokinesis, the microtubules of the mitotic spindle have been shown to play an important role in the positioning of the contractile microfilament ring assembly at the cell cortex (Maddoxa and Oegema, 2003). Microtubules have been implicated in steering the microfilament cytoskeleton in the proper direction, suggested by

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