AnArabidopsisGPI-Anchor Plasmodesmal Neck Protein with Callose Binding Activity and Potential to Regulate Cell-to-Cell Trafficking

Abstract

Plasmodesmata (Pds) traverse the cell wall to establish a symplastic continuum through most of the plant. Rapid and reversible deposition of callose in the cell wall surrounding the Pd apertures is proposed to provide a regulatory process through physical constriction of the symplastic channel. We identified members within a larger family of X8 domaincontaining proteins that targeted to Pds. This subgroup of proteins contains signal sequences for a glycosylphosphatidylinositol linkage to the extracellular face of the plasma membrane. We focused our attention on three closely related members of this family, two of which specifically bind to 1,3-b-glucans (callose) in vitro. We named this family of proteins Pd callose binding proteins (PDCBs). Yellow fluorescent protein-PDCB1 was found to localize to the neck region of Pds with potential to provide a structural anchor between the plasma membrane component of Pds and the cell wall. PDCB1, PDCB2, and PDCB3 had overlapping and widespread patterns of expression, but neither single nor combined insertional mutants for PDCB2 and PDCB3 showed any visible phenotype. However, increased expression of PDCB1 led to an increase in callose accumulation and a reduction of green fluorescent protein (GFP) movement in a GFP diffusion assay, identifying a potential association between PDCB-mediated callose deposition and plant cell-to-cell communication.

A calmodulin‐like protein regulates plasmodesmal closure during bacterial immune responses

“…In leaves, CML41‐GFP localizes to punctate spots at the cell periphery (Fig. 2a–c), patterning that is reminiscent of plasmodesmata (Thomas et al ., 2008; Simpson et al ., 2009). We confirmed CML41‐GFP was localized to plasmodesmata by co‐staining plasmodesmal callose in Arabidopsis with aniline blue (Fig.…”

Ultrastructural study of plasmodesmata in the brown alga Dictyota dichotoma (Dictyotales, Phaeophyceae)

“…Several other works noted additional internal substructures (Ding et al 1992b, Overall and Blackman 1996. Recently, PD-associated proteins have been identified in charophycean algae and land plants , Blackman and Overall 1998, Gestel et al 2003, Faulkner et al 2005, Sagi et al 2005, Thomas et al 2008, Simpson et al 2009, Faulkner and Maule 2010. These works suggested that there are highly complicated control mechanisms underlying the cell-to-cell molecular traffic via PD.…”

Grain setting defect1, Encoding a Remorin Protein, Affects the Grain Setting in Rice through Regulating Plasmodesmatal Conductance

“…Actin filaments associated with the desmotubule structure within the PD are believed to play a role in regulating the aperture of the cytoplasmic sleeve between the PM and desmotubule (Ding et al, 1996;Su et al, 2010). In addition, GPIanchored protein PDCB1 is also located in the PD structure and impacts PD function (Simpson et al, 2009). Overexpression of PDCB1 resulted in increased callose accumulation and changes in PD conductivity (Simpson et al, 2009).…”

“…Callose deposition can also impact the size of the PD aperture at the neck region (Radford et al, 1998;Levy et al, 2007) and callose synthase genes such as Glucan SynthaseLike7 (GSL7, also named CalS7), GSL8, and GSL12 have been shown to play a role in regulating symplastic trafficking (Guseman et al, 2010;Barratt et al, 2011;Vatén et al, 2011;Xie et al, 2011). Other proteins that have been shown to impact the structure and function of the PD include glycosylphosphatidylinositol (GPI)-anchored proteins, PD callose binding protein1 (PDCB1), which is also associated with callose deposition (Simpson et al, 2009), and LYSIN MOTIF DOMAIN-CONTAINING GLYCOSYLPHOSPHATIDYLINOSITOL-ANCHORED PROTEIN2, which limits the molecular flux through the PD by chitin perception (Faulkner et al, 2013). Changes in PD permeability can have major consequences for the translocation of photoassimilates needed for grain filling in rice.…”

“…PD are transverse cell wall channels structured with the cytoplasmic sleeve and the modified endoplasmic reticulum desmotubule between neighboring cells (Maule, 2008). A number of proteins affect the structure and functional performance of the PD, which in turn impacts the cell-to-cell transport of small and large molecules through the PD during plant growth, development, and defense (Cilia and Jackson, 2004;Sagi et al, 2005;Lucas et al, 2009;Simpson et al, 2009;Stonebloom et al, 2009). For example, actin and myosin, which link the desmotubule to the plasma membrane (PM) at the neck region of PD, are believed to play a role in regulating PD permeability by controlling PD aperture (White et al, 1994;Ding et al, 1996;Reichelt et al, 1999).…”