Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2020
Publication Date: 7/29/2020
Citation: Cooper, B., Campbell, K., Beard, H.S., Garrett, W.M., Ferreira, M.E. 2020. The Proteomics of Resistance to Halo Blight in Common Bean. Molecular Plant-Microbe Interactions. 33(9):1161-1175. https://doi.org/10.1094/MPMI-05-20-0112-R.
Interpretive Summary: Halo blight disease, caused by a bacterium, reduces harvests of the dry, edible common bean and reduces food security for the people who rely on beans for a primary source of nutrition. Natural resistance genes in the plant can provide protection to some strains but not others. In this study, we used mass spectrometry, an analytical technique, to measure the amounts of bean proteins in leaves inoculated with a halo blight strain that triggers resistance and with another strain that infects and causes disease. Out of more than 4,000 proteins evaluated, there were 29 that were specifically linked to resistance. Several of these bean proteins include receptor kinases that can sense bacteria and send signals within the plant to stimulate defense. Other bean proteins make chemicals needed for defense such as the production of phytoalexins that are toxic to bacteria. A gene for one of the kinases was tested by RNA silencing to reduce the amount of the RNA the gene made. As this reduced the activity of the gene, resistance was reduced, thus proving the gene was needed for resistance to halo blight. These results will be of interest to scientists in the government, at universities, and at private institutions who are interested in protecting beans from halo blight infection.
Technical Abstract: Halo blight disease of beans is caused by a Gram-negative bacterium, Pseudomonas syringae pv. phaseolicola (Pph). The disease is prevalent in South America and Africa and causes crop loss to indigent people who rely on beans as a primary source of daily nutrition. In susceptible beans, Pph causes water-soaking at the site of infection and produces phaseolotoxin, an inhibitor of bean arginine biosynthesis. In resistant beans, Php triggers the plant immune system and a hypersensitive response that limits the spread of infection. Here, we used high-throughput mass spectrometry to interrogate immune responses to two different Pph isolates on a single line of common bean, Phaseolus vulgaris PI G19833 with a reference genome sequence. We obtained quantitative information for 4,135 bean proteins. A subset of 160 proteins with similar accumulation changes in both susceptible and resistant plants, proteins that include salicylic acid responders EDS1 and NDR1, ethylene and jasmonic acid biosynthesis enzymes, and proteins enabling vesicle secretion revealed a basal defense that relies on hormonal response and the mobilization of extracellular proteins. A subset of 29 proteins specific to hypersensitive immunity included SOBIR1, a G-type lectin-receptor-like kinase, and enzymes needed for glucosinolate and phytoalexin production. Virus induced gene silencing revealed that the G-type lectin-receptor-like kinase suppresses bacterial infection. Together, the results define the proteomics of disease resistance to Pph in beans and support a model whereby the induction of hypersensitive immunity reinstates defenses targeted by Pph.