The Proteomics of Resistance to Halo Blight in Common Bean.

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, Pph triggers a hypersensitive response that limits the spread of infection. Here, we used high-throughput mass spectrometry to interrogate the 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 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 Pph in beans and support a model whereby the induction of hypersensitive immunity reinstates defenses targeted by Pph.