The Proteomics of Resistance to Halo Blight in Common Bean

Abstract

Halo blight disease of beans is caused by a gram-negative bacterium, Pseudomonas syringae pv. phaseolicola. The disease is prevalent in South America and Africa and causes crop loss for indigent people who rely on beans as a primary source of daily nutrition. In susceptible beans, P. syringae pv. phaseolicola causes water-soaking at the site of infection and produces phaseolotoxin, an inhibitor of bean arginine biosynthesis. In resistant beans, P. syringae pv. phaseolicola triggers a hypersensitive response that limits the spread of infection. Here, we used high-throughput mass spectrometry to interrogate the responses to two different P. syringae pv. phaseolicola 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 during both susceptible and resistant reactions included salicylic acid responders EDS1 and NDR1, ethylene and jasmonic acid biosynthesis enzymes, and proteins enabling vesicle secretion. These proteins revealed the activation of a basal defense involving hormonal responses 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 glucoside 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 P. syringae pv. phaseolicola in beans and support a model whereby the induction of hypersensitive immunity reinstates defenses targeted by P. syringae pv. phaseolicola.