Abstract Detail

Recent Topics Posters

Davidson, Andrea [1], Blahut-Beatty, Laureen [2], Itaya, Asuka [2], Zhang, Yunfang [2], Zheng, Suqin [2], Simmonds, Daina [3].

Oxalic Acid Function in Sclerotinia sclerotiorum infection.

Sclerotinia sclerotiorum has a very broad host range of more than 400 plant species. The success of this necrotrophic fungus is largely dependent on its major virulence factor, oxalic acid (OA). Virulence is lost in S. sclerotiorum mutants that don’t secrete OA (1) while transgenic plants that express OA degrading enzymes, e.g. oxalate oxidase (OxO) have greater resistance (2). In order to gain a better understanding of OA function, we conducted a temporal and spatial study of S. sclerotiorum infection and OA concentration on excised leaves of X5 (susceptible) and 20B7 (resistant OxO transgenic) soybean lines. Initiation of S. sclerotiorum infection and its progression differ in the two lines. Microscopy revealed that initiation of infection is similar in both lines, but once established, proceeds at a slower rate, or stops in resistant 20B7 transgenic tissue.  Oxalic acid concentration was at basal levels in both lines at early stages of infection, 1-2 days post inoculation (dpi). However, once infection is established, 3-5 dpi, infection spread rapidly throughout the susceptible X5 tissue and concomitantly OA concentration increased dramatically. Oxalic acid levels remained low in 20B7 due to OxO degradation of OA that resulted in slow spread of infection. This underscores the role of OA in enabling the fungus to invade live plant cells once infection is established. However, infection was initiated in leaves expressing high levels of OxO activity and basal levels of OA, indicating that OA was not needed in early stages of infection or perhaps that at low concentrations OA has a different role. This suggests to us that the fungus uses a different strategy to establish infection.
1. Godoy et al., 1990, Physiol. Mol. Plant Pathol. 37:179-191.
2. Donaldson et al., 2001, Physiol. Mol. Plant Pathol. 59:297-307.

1 - Longfields-Davidson Heights Secondary School, Science Department, 149 Berringer Dr., Nepean, Ontario, K2J 5C6, Canada
2 - Agriculture and Agri-Food Canada, 960 Carling Ave, Ottawa, ON, K1A 0C6, canada
3 - Agriculture and Agri-Food Canada, Genomics and Biotechnology, 960 Carling Ave, Ottawa, ON, K1A 0C6, Canada

Keywords:
Sclerotinia sclerotiorum 
oxalic acid
necrotrophic pathogen
oxalate oxidase
transgenic plants
Soybean.

Presentation Type: Recent Topics Poster
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PRT054
Abstract ID:1840
Candidate for Awards:None