Differential plant response to toxins and elicitor proteins released by the potato and tomato pathogens Alternaria solani and Alternaria alternata

Authors: Jones, Richard; Perez, Frances

Submitted to: Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2022
Publication Date: 12/5/2022
Citation: Jones, R.W., Perez, F.G. 2022. Differential plant response to toxins and elicitor proteins released by Alternaria solani. Journal of Plant Pathology. https://doi.org/10.1007/s42161-022-01286-w.
DOI: https://doi.org/10.1007/s42161-022-01286-w

Interpretive Summary: Early blight disease, caused by a fungus, affects various crop plants, with the greatest impact on potato and tomato, the two most valuable vegetable crops. It is not clear why the disease symptoms vary between different cultivars and plants of different age. Via testing of different compounds released by the fungus during infection, individual chemical and protein components were identified that contribute to disease symptom differences. This information can now be used to engineer resistance based on blocking the activity of the compounds shown to cause disease symptoms. This information will also be useful in understanding the best ways that breeders can screen for resistance to this disease.

Technical Abstract: Early blight of potato and tomato, caused principally by Alternaria solani, results in extensive damage to foliar tissues. Symptoms are seen as expanding necrotic lesions. Lesions are sometimes surrounded by a halo of chlorotic tissue, however the basis for presence or absence of the distinctive halo have not been determined. In an effort to dissect the basis for lesion development a series of Alternaria-associated toxins and potential elicitor proteins were tested in potato and tobacco. Infiltration of leaves demonstrated that, while most of the pure toxins did not have a visible effect, two anthraquinones, bostrycin and altersolanon A, elicited a necrosis-mediated response. Extracts of solid and liquid cultures of A. solani yielded anthraquinones that also elicited a necrotic response. Responses were similar regardless of leaf age. Two potential elicitor proteins were identified and cloned from A.solani. Agro-infiltration-based expression of cel12-A and Hrip revealed that cel12-A had no apparent effect, whereas Hrip induced expanding tissue death and development of chlorotic halos. Development of tissue death and chlorotic halos was dependent on leaf age, with older leaves exhibiting halos. It is proposed that toxin and elicitor production, in conjunction with tissue susceptibility mediate the outcomes of early blight symptoms.