PDLPs

PDLPs, or plasmodesmata-located proteins, are a family of plant membrane proteins that localize to plasmodesmata—the cytoplasmic channels that connect neighboring plant cells across the cell wall. In Arabidopsis thaliana and other species, multiple PDLP genes have been identified, and related proteins are found across the plant kingdom. PDLPs are typically small single-pass transmembrane proteins with an extracellular domain and a short cytoplasmic tail, and they are enriched at plasmodesmata as shown by fluorescent tagging and localization studies.

Functionally, PDLPs are involved in regulating plasmodesmatal permeability, thereby modulating intercellular transport of signaling molecules, nutrients, and other macromolecules. A common mechanistic theme is that PDLPs influence callose deposition at the plasmodesmatal neck region, which constricts the channel and reduces trafficking between cells. PDLP5 is the best-characterized member; its overexpression leads to reduced intercellular movement and increased callose at plasmodesmata, while loss-of-function mutations can have the opposite effect. Other PDLPs are thought to have related roles in development and defense, and their activity can be responsive to hormonal and stress signals, including salicylic acid.

Role in defense and development: By controlling plasmodesmatal gating, PDLPs affect plant growth, tissue patterning, and responses to pathogen attack. Since many pathogens and viruses spread cell-to-cell through plasmodesmata, PDLPs are implicated in defense as regulators of intercellular movement, potentially restricting pathogen spread through enhanced callose-based closure.

Research and tools: PDLP function is studied using genetic mutants, overexpression lines, and subcellular localization with fluorescent fusion proteins, alongside assays of plasmodesmatal transport and callose dynamics. The field continues to clarify the specific interactions and signaling networks that connect PDLP activity to callose synthases and other plasmodesmal regulators.