Search Results (2)

A highly aggressive strain (CMN14-5-1) of Clavibacter nebraskensis bacteria, which causes Goss’s wilt in corn, induced severe symptoms in a susceptible corn line (CO447), resulting in water-soaked lesions followed by necrosis within a few days. A tolerant line (CO450) inoculated with the same strain exhibited only mild symptoms such as chlorosis, freckling, and necrosis that did not progress after the first six days following infection. Both lesion length and disease severity were measured using the area under the disease progression curve (AUDPC), and significant differences were found between treatments. We analyzed the expression of key genes related to plant defense in both corn lines challenged with the CMN14-5-1 strain. Allene oxide synthase (ZmAOS), a gene responsible for the production of jasmonic acid (JA), was induced in the CO447 line in response to CMN14-5-1. Following inoculation with CMN14-5-1, the CO450 line demonstrated a higher expression of salicylic acid (SA)-related genes, ZmPAL and ZmPR-1, compared to the CO447 line. In the CO450 line, four genes related to programmed cell death (PCD) were upregulated: respiratory burst oxidase homolog protein D (ZmrbohD), polyphenol oxidase (ZmPPO1), ras-related protein 7 (ZmRab7), and peptidyl-prolyl cis-trans isomerase (ZmPPI). The differential gene expression in response to CMN14-5-1 between the two corn lines provided an indication that SA and PCD are involved in the regulation of corn defense responses against Goss’s wilt disease, whereas JA may be contributing to disease susceptibility. Full article

The Gram-positive bacterium Clavibacter nebraskensis (Cn) causes Goss’s wilt and leaf blight on corn in the North American Central Plains with yield losses as high as 30%. Cn strains vary in aggressiveness on corn, with highly aggressive strains causing much more serious symptoms and damage to crops. Since Cn inhabits the host xylem, we investigated differences in the secreted proteomes of Cn strains to determine whether these could account for phenotypic differences in aggressiveness. Highly and a weakly aggressive Cn strains (Cn14-15-1 and DOAB232, respectively) were cultured, in vitro, in the xylem sap of corn (CXS; host) and tomato (TXS; non-host). The secretome of the Cn strains were extracted and processed, and a comparative bottom-up proteomics approach with liquid chromatography–tandem mass spectrometry (LC–MS/MS) was used to determine their identities and concentration. Relative quantitation of peptides was based on precursor ion intensities to measure protein abundances. In total, 745 proteins were identified in xylem sap media. In CXS, a total of 658 and 396 proteins were identified in strains Cn14-5-1 and DOAB232, respectively. The unique and the differentially abundant proteins in the secretome of strain Cn14-5-1 were higher in either sap medium compared to DOAB232. These proteins were sorted using BLAST2GO and assigned to 12 cellular functional processes. Virulence factors, e.g., cellulase, β-glucosidase, β-galactosidase, chitinase, β-1,4-xylanase, and proteases were generally higher in abundance in the aggressive Cn isolate. This was corroborated by enzymatic activity assays of cellulase and protease in CXS. These proteins were either not detected or detected at significantly lower abundance levels in Cn strains grown in non-host xylem sap (tomato), suggesting potential factors involved in Cn–host (corn) interactions. Full article