Relationship of bacterial growth and chemical events in the leaf apoplast during susceptible and resistant interactions

Authors: Baker, Con; MOCK, NORTON - Retired ARS Employee; AVERYANOV, ANDREY - Collaborator

Submitted to: Physiological and Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2017
Publication Date: 11/20/2017
Citation: Baker, C.J., Mock, N.M., Averyanov, A.A. 2017. Relationship of bacterial growth and chemical events in the leaf apoplast during susceptible and resistant interactions . Physiological and Molecular Plant Pathology. 102:17-23. 10.1016/j.pmpp.2017.11.005.
DOI: https://doi.org/10.1016/j.pmpp.2017.11.005

Interpretive Summary: Bacterial plant diseases cause major damage to crops each year and the cost of controlling them adds greatly to production costs and often involves antibiotics which are a public concern. The plant leaf apoplast, which is the cell wall region just outside the plant cell itself, is the first line of defense against most aerial pathogens. In this study we correlated bacterial growth with early chemical responses in the apoplast during the first 10 h of three types of interactions: saprophytic, susceptible, or resistant. This information defines the time by which control measures need to be engaged, and will benefit plant scientists and breeders who are devising new strategies to improve disease resistance in plants as well as decrease the use of chemical pesticides and antibiotics.

Technical Abstract: The leaf apoplast is the first battleground for plant pathogens invading via stomata. The apoplast is the border just outside the cell membrane and in a leaf, much of the apoplast is in direct contact or near the air space within the leaf. It is one of the most accessible parts of the plant for the study of early events in the bacteria/plant interactions and likewise it offers lucrative possibilities for plant disease control. Recent studies have shown that several phenolics respond to bacterial infection within the first few hours after inoculation. Two in particular, acetovanillone and acetosyringone, vary in their timing and concentrations depending on the type of interaction: saprophytic, susceptible, or resistant. A second phase occurs in pathogenic interactions, about 10 h post inoculation, and involves a dramatic increase of chlorogenic acid into the apoplast. Chlorogenic acid is stored in the plant vacuole and its appearance indicates leakage across the apoplast/symplast (A/S) barrier, which in turn is likely to affect bacterial growth. Therefore we have tried to correlate bacterial multiplication with these chemical events in the three types of interactions. The oxidative environment of the apoplast during these early periods suggests that these phenolic compounds may influence the redox environment and directly inhibit bacterial multiplication during certain periods of the interactions.