Symplastic intercellular transport from a developmental perspective

Journal of Experimental Botany, Apr 2014

Plant cells have channel-like structures named plasmodesmata that allow for the symplastic molecular transport between neighbouring cells. The importance of plasmodesmata in whole plant development is well acknowledged. They mediate the cell-to-cell and vascular loading and unloading of metabolites, proteins, and other signalling molecules. However, it is still not clear how, mechanistically, these channels are regulated in response to developmental and environmental cues. This review aims to bring together knowledge acquired in recent years on plasmodesmata composition, regulation, and function. Progress in the discovery of factors that regulate symplastic transport and plant development in particular are discussed. This will hopefully highlight the challenges faced by the scientific community to unveil the mechanisms controlling symplastic communication during the formation and maintenance of plant meristems.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

https://jxb.oxfordjournals.org/content/65/7/1857.full.pdf

Symplastic intercellular transport from a developmental perspective

Journal of Experimental Botany Symplastic intercellular transport from a developmental perspective Yoselin Benitez-Alfonso 0 0 Centre for Plant Sciences, School of Biology, University of Leeds , Leeds LS2 9JT , UK Plant cells have channel-like structures named plasmodesmata that allow for the symplastic molecular transport between neighbouring cells. The importance of plasmodesmata in whole plant development is well acknowledged. They mediate the cell-to-cell and vascular loading and unloading of metabolites, proteins, and other signalling molecules. However, it is still not clear how, mechanistically, these channels are regulated in response to developmental and environmental cues. This review aims to bring together knowledge acquired in recent years on plasmodesmata composition, regulation, and function. Progress in the discovery of factors that regulate symplastic transport and plant development in particular are discussed. This will hopefully highlight the challenges faced by the scientific community to unveil the mechanisms controlling symplastic communication during the formation and maintenance of plant meristems. Intercellular communication; meristem development; plasmodesmata; plasmodesmata proteins; plasmadesmata regulation; symplastic transport - © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: of complex genetic and proteomic screens in different laboratoriess (Faulkner and Maule, 2011). New information has also been gained on the function of PD proteins, intracellular and extracellular regulators, and of mobile factors in the regulation of plant growth, organ patterning, and stress response in model and non-model organisms. This review compiles part of this information, focusing on recent evidence supporting or clarifying the role of symplastic transport in the initiation and maintenance of primary and secondary meristems. Identification of plasmodesmata proteins The proteomic analysis of digested cell walls represented a significant step towards the elucidation of PD molecular composition (Faulkner and Maule, 2011; Fernandez-Calvino et al., 2011; Salmon and Bayer, 2012). A number of proteins identified using this approach have been confirmed to target PDs in stable transgenic lines. These include PlasmoDesmataLocated Proteins (PDLPs), PlasmoDesmata Callose Binding proteins (PDCBs), Glycosyl Hydrolases family 17 (GHL17; BG), Receptor Like Kinases (RLK), etc. Some of these proteins (or families of proteins) have been characterized and their role in PD regulation and plant development has been studied (Thomas et al., 2008; Simpson et al., 2009; BenitezAlfonso et al., 2013; Faulkner et al., 2013). So far, no common molecular signature has been identified among PD proteins and, therefore, it is difficult to distinguish them (based on their sequence) from other secreted or plasma membranetargeted proteins, and/or from other family members playing redundant and non-redundant functions in the cell. Genetic and functional redundancy between PD proteins may have hindered their identification through genetic screens. Almost simultaneously, two forward genetic approaches were pursued to isolate PD mutants (Kobayashi et al., 2007; Benitez-Alfonso et al., 2009; Stonebloom et al., 2009; Xu et al., 2011, 2012). In both instances, intracellular regulators rather than PD-linked components were identified (see below). Similarly, an enhancer genetic screen using as the starter line the erl1erl2 mutant (defective in stomata differentiation) identified KOBITO1 as a regulator of PD permeability in epidermal pavement cells (Kong et al., 2012). Highlighting the importance of PD in vascular transport, screening for mutants in phloem transport successfully identified gain-of-function mutations in the PD protein Callose Synthase 3 (CALS3). CALS3 acts in the phloem where it controls symplastic connectivity and vascular development (Vaten et al., 2011). Alternative proteomic strategies have enriched the list of confirmed PD proteins in model and non-model species. For example, affinity purification of interactors, using as bait the non-cell autonomous protein CmPP16, identified PD-located Germin like proteins (Ham et al., 2012). Similar methodology, in this case using as bait PD-associated calreticulin, revealed PD-localization for a member of the glycosyltransferase-like family (Zalepa-King and Citovsky, 2013). Comparative genomic approaches have been useful for the identification of PD proteins in other species. Orthologues of Arabidopsis PD-located β-1,3 glucanases were identified in poplar. Localization and expression studies of these proteins revealed a novel role for members of this family in bud dormancy release (Rinne et al., 2011). In summary, despite major challenges in the isolation of PDs from cell walls, the combined use of genetic, proteomic, and cell biology approaches has led to the ide (...truncated)


This is a preview of a remote PDF: https://jxb.oxfordjournals.org/content/65/7/1857.full.pdf

Yoselin Benitez-Alfonso. Symplastic intercellular transport from a developmental perspective, Journal of Experimental Botany, 2014, pp. 1857-1863, 65/7, DOI: 10.1093/jxb/eru067