Abstract Detail

Basic and applied approaches to improve disease resistance in plants

Cameron, Robin K. [1], Carella, Phil [1], Isaacs, Marisa [1], Champigny, Marc [2], Merl-Pham, Juliane [3], Dey, Sanjukta [4], Vlot-Schuster, Corina [4].

Using DIR1 to investigate long distance signal movement during Systemic Acquired Resistance.

During Systemic Acquired Resistance (SAR), a SAR-inducing infection in one leaf initiates movement of phloem-mobile signals to uninfected distant leaves to prime plants to respond in a resistant manner to future infections. Our early work with the dir1-1 (defective in induced resistance) mutant demonstrated that DIR1 is required for SAR and led to the hypothesis that DIR1, a lipid transfer protein (LTP), moves to distant leaves to activate SAR. To demonstrate that DIR1 moves to distant leaves during SAR, we monitored DIR1-GFP accumulation in phloem exudates using an estrogen-SAR assay, in which estrogen treatment induces DIR1-GFP expression in one leaf of dir1-1, followed by SAR-induction in the same leaf. DIR1-GFP was detected in exudates collected from local and distant leaves of SAR-induced plants using both DIR1 and GFP antibodies providing compelling evidence that DIR1 moves via the phloem to distant leaves to initiate priming. Our work fills a major gap in the SAR field as no other putative SAR mobile signal has been shown to move in planta to distant leaves. To discover how DIR1 enters the phloem we took advantage of plant lines with compromised cell-to-cell movement caused by overexpression of Plasmodesmata-Located Proteins. These lines were defective for SAR and DIR1 was not observed in distant leaf phloem exudates, supporting the idea that cell-to-cell movement of DIR1 through plasmodesmata is important for SAR signal movement. To discover new phloem proteins that play a role during SAR we compared phloem exudate proteomes collected from mock- and SAR-induced leaves using quantitative LC-MS/MS. Numerous proteins were enriched in SAR-induced versus mock-induced phloem exudates and T-DNA knock-out lines in some of these genes were SAR-defective indicating they contribute to SAR. Identification of SAR-specific phloem proteins may provide clues as to the protein complement of a high molecular weight DIR1-containing complex found in phloem exudates only after SAR induction. DIR1 is the best-characterized proteinaceous component of the mobile SAR signal complex. We will take advantage of DIR1’s proteinaceous nature and roles in both SAR-induced and distant leaves to identify proteins in the high molecular weight mobile signal complex, proteins associated with phloem loading of SAR signals and proteins involved in DIR1 perception in distant leaves.

1 - McMaster University, Biology, 1280 Main St W, Hamilton, ON, L8s 4K1, Canada
2 - University of Toronto, Scarborough, Biological Sciences, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada
3 - Helmholtz Zentrum Muenchen, Core Facility Proteomics, Munich, Germany
4 - Helmholtz Zentrum Muenchen, Institute of Biochemical Plant Pathology, Munich, Germany

Keywords:
Systemic aquired resistance
DIR1
phloem proteome
mobile signals
cell-to-cell movement.

Presentation Type: Symposium Presentation
Session: SY05
Location: Salon 2/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 1:45 PM
Number: SY05002
Abstract ID:434
Candidate for Awards:None