The Plasmodesmal Protein PDLP1 Localises to Haustoria-Associated Membranes during Downy Mildew Infection and Regulates Callose Deposition

Abstract

The downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa) is a filamentous oomycete that invades plant cells via sophisticated but poorly understood structures called haustoria. Haustoria are separated from the host cell cytoplasm and surrounded by an extrahaustorial membrane (EHM) of unknown origin. In some interactions, including Hpa-Arabidopsis, haustoria are progressively encased by host-derived, callose-rich materials but the molecular mechanisms by which callose accumulates around haustoria remain unclear. Here, we report that PLASMODESMATA-LOCATED PROTEIN 1 (PDLP1) is expressed at high levels in Hpa infected cells. Unlike other plasma membrane proteins, which are often excluded from the EHM, PDLP1 is located at the EHM in Hpa-infected cells prior to encasement. The transmembrane domain and cytoplasmic tail of PDLP1 are sufficient to convey this localization. PDLP1 also associates with the developing encasement but this association is lost when encasements are fully mature. We found that the pdlp1,2,3 triple mutant is more susceptible to Hpa while overexpression of PDLP1 enhances plant resistance, suggesting that PDLPs enhance basal immunity against Hpa. Haustorial encasements are depleted in callose in pdlp1,2,3 mutant plants whereas PDLP1 over-expression elevates callose deposition around haustoria and across the cell surface. These data indicate that PDLPs contribute to callose encasement of Hpa haustoria and suggests that the deposition of callose at haustoria may involve similar mechanisms to callose deposition at plasmodesmata.

Extracellular Vesicles Isolated from the Leaf Apoplast Carry Stress-Response Proteins

“…PATL1 and PATL2 both bind phosphoinositides and are thought to mediate vesicle transport and/or fusion (Petersen et al, 2014). PATL1 has been localized to the cell plate in dividing cells but also associates with PLASMODESMATA-LOCATED PROTEIN1 (PDLP1) during downy mildew infection and may colocalize with PDLP1 at the extrahaustorial membrane (Caillaud et al, 2014). We confirmed the presence of both PATL1 and PATL2 in the P40 fraction using anti-PATL antibodies (Peterman et al, 2004;Deng et al, 2007; Fig.…”

Homologues of the RPW8 Resistance Protein Are Localized to the Extrahaustorial Membrane that Is Likely Synthesized De Novo

“…In this regard, it is worth noting that several PM-proteins (PEN1, FLS2, and REM1.3, PDLP1, etc. ), Golgi marker proteins (SYP32 and Got1p) and endosomal markers (RabC1 and Ara7) were found in the perihaustorial membrane encasing oomycete haustoria in tobacco or Arabidopsis cells (Lu et al, 2012;Bozkurt et al, 2014;Caillaud et al, 2014). However, based on our observations, PM-localized proteins such as GFP-PEN1 ) and YFP-SYP131 (Fig.…”

NbCSPR underlies age-dependent immune responses to bacterial cold shock protein in Nicotiana benthamiana

“…Proteins were extracted and coIP performed as described using anti-GFP (ChromoTek) (38). LC-MS/MS, software processing, and peptide identification were performed as described (39) with the difference that a combined Sol genomics/TGAC N. benthamiana predicted protein database was used for protein identification.…”