A protein phosphatase 2A complex spatially controls plant cell division

Abstract

In the absence of cell migration, the orientation of cell divisions is crucial for body plan determination in plants. The position of the division plane in plant cells is set up premitotically via a transient cytoskeletal array, the preprophase band, which precisely delineates the cortical plane of division. Here we describe a protein complex that targets protein phosphatase 2A activity to microtubules, regulating the transition from the interphase to the premitotic microtubule array. This complex, which comprises TONNEAU1 and a PP2A heterotrimeric holoenzyme with FASS as regulatory subunit, is recruited to the cytoskeleton via the TONNEAU1-recruiting motif family of proteins. Despite the acentrosomal nature of plant cells, all members of this complex share similarity with animal centrosomal proteins involved in ciliary and centriolar/centrosomal functions, revealing an evolutionary link between the cortical cytoskeleton of plant cells and microtubule organizers in other eukaryotes.

PP2A-3 interacts with ACR4 and regulates formative cell division in the Arabidopsis root

“…2 A and B and SI Appendix, Fig. S1) (34). However, this doublemutant phenotype appeared to be less severe than the one obtained by Ballesteros and coworkers (36), which is possibly due to the use of different T-DNA lines.…”

“…In general, the PP2A heterotrimeric holoenzyme, which is a major, highly conserved eukaryotic serine/ threonine phosphatase, consists of a catalytic C subunit, a type A scaffolding/regulatory subunit, and a type B regulatory subunit (31). In Arabidopsis, PP2A phosphatases have been implicated in various hormone-regulated, cellular, and developmental processes, including spatial control of cell division and columella organization, and in innate immunity, but little is known about their dynamic and highly regulated function (32)(33)(34)(35). In the context of our focus on formative cell division, we selected PP2A-3 (and PP2A-4) for subsequent in-depth functional characterization.…”

Microtubules in Plants

“…The deposited factors at the selected plasma membrane site then guide the centrifugal expansion of the cell plate to this site (van Damme, 2009;Rasmussen et al, 2013). Among several proteins that have been identified to function in PPB-dependent division plane determination, TONNEAU1 (At3g55000; TON1), its interacting partners, and the TON2/FASS (At5g18580)-containing protein phosphatase PP2A complex, are required for PPB formation and share unexpected sequence homology with animal proteins that localize to the centrosomes (Spinner et al, 2013). Since the site of MT nucleation is not centralized to a cellular structure in plant cells, such as the centrosome in animal cells, the functional significance of this sequence conservation in evolutionary distant organisms is unclear.…”

Eukaryotic Flagella: Variations in Form, Function, and Composition during Evolution

“…It suggests further flagellum-associated proteins may await discovery in land plants that do not build flagella. TONNEAU1 is required for normal cell morphogenesis: it orchestrates organization of the cortical microtubule cytoskeleton, interacts with the classic MTOC protein centrin, and has most recently been detected in a protein complex containing TONNEAU2 (Azimzadeh et al 2008, Spinner et al 2010, Spinner et al 2013. In other work, a screen for TONNEAU1-interacting proteins identified a novel family of 34 proteins that share in common six short sequence motifs; conservation of some of these motifs, including their order of appearance, is evident in another animal centrosomal protein, CEP350 (Drevensek et al 2012).…”