# Regulation of Plasmodesmata Function Through Lipid-Mediated PDLP7 or PDLP5 Strategies in Arabidopsis Leaf Cells

## TL;DR

This study explores how PDLP7 and PDLP5 proteins regulate plasmodesmata function through interactions with lipids in Arabidopsis leaf cells.

## Contribution

The paper reveals that PDLP7 and PDLP5 form dimers only in the presence of sphingolipids, influencing membrane order and stress responses.

## Key findings

- PDLP7 alters sphingolipid composition in plasmodesmata, particularly GIPC content, affecting membrane order.
- Sphingolipids influence the oligomeric state of PDLP7 in membranes, promoting aggregation in vivo.
- Co-overexpression of PDLP7 and PDLP5 disrupts their plasmodesmata localization and upregulates PR1.

## Abstract

Plasmodesmata (PDs) are enriched in sphingolipids and sterols, creating a specialized environment for regulatory proteins like plasmodesmata-localized proteins (PDLPs). How PDLPs regulate PD function in a specific lipid environment remains poorly understood. Here, we provide a unique insight from the interaction network of two different PDLPs together with sphingolipids and propose a concept that PDLPs form homo- or hetero-dimers only in the presence of sphingolipids. Located in the detergent resistance region, PDLP7 demonstrated the ability to influence the sphingolipid composition in PD-enriched fraction, particularly the GIPC content, and finally, modulating the membrane order. The presence of sphingolipids, in turn, affected the oligomeric state of PDLP7 in membranes. The PDLP7 recombinant protein existed as a monomer in vitro, but it formed self-aggregates in yeast and plant cells. We further examined PDLP5, another known phytosphinganine (t18:0)-specific binding PDLP, alongside PDLP7, and confirmed a similar interaction pattern: no direct interaction was observed in vitro, but interactions were noted in vivo. Co-overexpression of the two disrupted their PD localization and induced the upregulation of pathogenesis-related protein 1 (PR1). In summary, we gained insights into the network of PDLPs with lipids and propose that PDLPs were under precise regulation during plant development and stress responses.