Plasmodesmata dynamics are coordinated by intracellular signaling pathways

Abstract

Membrane-lined channels called plasmodesmata (PD) connect the cytoplasts of adjacent plant cells across the cell wall, permitting intercellular movement of small molecules, proteins, and RNA. Recent genetic screens for mutants with altered PD transport identified genes suggesting that chloroplasts play crucial roles in coordinating PD transport. Complementing this discovery, studies manipulating expression of PD-localized proteins imply that changes in PD transport strongly impact chloroplast biology. Ongoing efforts to find genes that control root and stomatal development reveal the critical role of PD in enforcing tissue patterning, and newly discovered PD-localized proteins show that PD influence development, intracellular signaling, and defense against pathogens. Together, these studies demonstrate that PD function and formation are tightly integrated with plant physiology.

Importance of symplasmic communication in cell differentiation

“…The movement of NCAPs related to cell differentiation is regulated by as yet unknown mechanisms, that precisely guide proteins to the specific individual cells (like TTG1, CPC, CPL) or cell layers (like KN1; for a review see refs. 16,17). Interactions between NCAPs and PD are not well understood, although the motifs crucial for symplasmic transport of different proteins have been described 17 , 50 , 51 …”

Plasmodesmata: a signaling hub at the cellular boundary

“…In the symplasmic pathway, signaling molecules are commonly thought to move cytoplasmically through the PD that connect signal-generating cells to their adjacent recipient cells [4]. The protein composition and the molecular architecture of PD are yet to be discovered, but an increasing number of proteins has been identified to localize or partially associate with PD [5-7]. Certain plasma membrane (PM)-localized receptor-like kinases (RLKs) and membrane-anchored proteins are also found to associate with PD.…”

Arabidopsis mutants in sphingolipid synthesis as tools to understand the structure and function of membrane microdomains in plasmodesmata

“…Imaging techniques that allow preservation of PD structure revealed a very complex and refined organization, but its molecular composition is difficult to dissect by biochemical approaches (Brunkard et al, 2013; Salmon and Bayer, 2013). However, PD are stable assemblies that can be found in cell wall preparations (Brecknock et al, 2011; Salmon and Bayer, 2013) and can even survive treatments involving cell autophagy (Figure 1).…”

“…The fact that the PDLP5 resides exclusively in the center of the PD cavity, reinforces the hypothesis that this protein is located in microdomains. Signaling mechanism controlling PD function has been suggested (Brunkard et al, 2013) but it is possible that the lipidic environment is essential for certain proteins in order to keep its position in PD. In this regard, the hypothesis is that the components of the PM could sense the accumulation of the protein in order to initiate the response that will recruit callose synthases (Wang et al, 2013).…”

“…It is reasonable to expect that the control of the flow under infection conditions depends on intrinsic characteristics of the PD pore determining its size and selectivity, but also from other extrinsic ones, as concentration gradients of transit molecules as sRNAs. In fact, some of these regulatory factors originate in the chloroplast (Brunkard et al, 2013). Regarding the residence of molecules responsible of the signaling implied in the regulation of the aperture/closure of the PD pore, a significant number of receptor-like kinases has been described in PD proteomic studies (Fernandez-Calvino et al, 2011), thus suggesting that these proteins may have a crucial role in determining the changes of PD structure upon infection (Lee and Lu, 2011).…”