Abstract

Many filamentous plant pathogens place specialized feeding structures, called haustoria, inside living host cells. As haustoria grow, they are believed to manipulate plant cells to generate a specialized, still enigmatic extrahaustorial membrane (EHM) around them. Here, we focused on revealing properties of the EHM. With the help of membrane-specific dyes and transient expression of membrane-associated proteins fused to fluorescent tags, we studied the nature of the EHM generated by barley leaf epidermal cells around powdery mildew haustoria. Observations suggesting that endoplasmic reticulum (ER) membrane-specific dyes labelled the EHM led us to find that Sar1 and RabD2a GTPases bind this membrane. These proteins are usually associated with the ER and the ER/cis-Golgi membrane, respectively. In contrast, transmembrane and luminal ER and Golgi markers failed to label the EHM, suggesting that it is not a continuum of the ER. Furthermore, GDP-locked Sar1 and a nucleotide-free RabD2a, which block ER to Golgi exit, did not hamper haustorium formation. These results indicated that the EHM shares features with the plant ER membrane, but that the EHM membrane is not dependent on conventional secretion. This raises the prospect that an unconventional secretory pathway from the ER may provide this membrane's material. Understanding these processes will assist future approaches to providing resistance by preventing EHM generation.

Keywords

Barley organelle markers; endoplasmic reticulum (ER); extrahaustorial membrane (EHM); powdery mildew; Rab GTPase; Sar1 GTPase; secretion

Published in

Journal of Experimental Botany
2017, Volume: 68, number: 21-22, pages: 5731-5743
Publisher: OXFORD UNIV PRESS

Associated SLU-program

SLU Plant Protection Network


UKÄ Subject classification

Biochemistry and Molecular Biology


Publication identifier

DOI: https://doi.org/10.1093/jxb/erx403

Permanent link to this page (URI)

https://res.slu.se/id/publ/93540