The Type IIArabidopsisFormin14 Interacts with Microtubules and Microfilaments to Regulate Cell Division  

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.

Formins at a glance

“…In vivo observations have long suggested that formins also regulate MT organization and dynamics (Kikyo et al, 1999;Lee et al, 1999;Chang, 2000;Ishizaki et al, 2001;Kato et al, 2001;Leader et al, 2002;Deeks et al, 2010;Li et al, 2010). Expression of constitutively active mDia constructs results in co-alignment of MTs and actin fibers , promotes MT targeting to the cell periphery (Yamana et al, 2006;Goulimari et al, 2008;Zaoui et al, 2010) and stabilizes MTs (Palazzo et al, 2001;Wen et al, 2004;Eng et al, 2006;Bartolini et al, 2008).…”

BENT UPPERMOST INTERNODE1Encodes the Class II Formin FH5 Crucial for Actin Organization and Rice Development

“…It was shown very recently that several Arabidopsis formins interact directly with microtubules (Deeks et al, 2010;Li et al, 2010), which prompted us to determine whether FH5 interacts with microtubules. To test this, we first performed microtubule cosedimentation assays.…”

“…Recent results from the moss Physcomitrella patens demonstrated that class II formins could elongate actin filaments at an amazingly rapid rate and are essential for polar cell expansion (Vidali et al, 2009). Most recently, a class II formin, AFH14, was reported to bind both microtubules and microfilaments and was shown to play important roles in cell division and microspore formation in Arabidopsis (Li et al, 2010). However, it remains a major challenge to explore the physiological functions of each formin protein in plants, particularly in the model cereal rice, for which no single formin has been functionally characterized.…”

CASEIN KINASE1-LIKE PROTEIN2 Regulates Actin Filament Stability and Stomatal Closure via Phosphorylation of Actin Depolymerizing Factor

“…Actin filaments are highly dynamic, undergoing rapid reorganization and turnover regulated by actin binding proteins such as ADF/cofilin, villin, profilin, fimbrin, and capping protein (Wasteneys and Galway, 2003;Hussey et al, 2006;Staiger and Blanchoin, 2006;Higaki et al, 2007;Thomas et al, 2009;Li et al, 2010;Su et al, 2012;Qu et al, 2013;Wang et al, 2015). ADF/cofilin proteins function as key regulators of actin filament dynamics and reorganization through binding to both globular and filamentous actin.…”