Submitted to: Physiological and Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2012
Publication Date: 1/15/2012
Citation: Baker, C.J., Kovalskaya, N.U., Mock, N.M., Owens, R.A., Deahl, K.L., Whitaker, B.D., Roberts, D.P., Hammond, R., Averyanov, A.A. 2012. An internal standard technique for improved quantitative analysis of apoplastic metabolites in tomato leaves. Physiological and Molecular Plant Pathology. 78:31-37. Interpretive Summary: Plant diseases cause major losses to farmers each year. The plant leaf is the site of the first line of defense against many foliar pathogens. There are several chemicals in the leaf that have the ability to regulate the interaction between a plant and foliar pathogens. These chemical regulators may determine whether the interaction will be resistant or susceptible. Here we report the development of a technique with increased precision to measure subtle changes in these chemicals as disease or resistance develops in the leaf. This was done by using an internal standard that we could put into the plant. By being aware of and being able to quantify these chemical regulators we will improve our understanding of the biochemical basis for plant resistance to disease. This information will be of use to plant scientists who are devising new strategies to improve disease resistance in plants.
Technical Abstract: The purpose of this study was to establish a technique with sufficiently precision to monitor subtle changes in the concentration of apoplastic metabolites in tomato leaves. The plant apoplast is the site of the first line of defense against many foliar pathogens. This aqueous layer lining the airspace is enriched with secondary metabolites that can serve many roles including cell wall reinforcement as well as protection from environmental hazards, both biotic and abiotic. Previous studies with cell suspension cells demonstrated that the composition of the phenolics in the extracellular fluid was very responsive to inoculation with bacterial pathogens and pathogen elicitors. In tomato plants we also detect a compositional change in apoplastic phenolics of leaves as they became infected with the Potato Spindle Tuber viroid. Many of these metabolites are known to be redox sensitive and some are likely to possess bioactive properties. We needed a better technique to quantify subtle changes in the apoplast metabolites. Here we introduced the use of an internal standard that was found to be redox insensitive and did not bind to the cell wall matrix.