Defense mechanisms of Solanum tuberosum L. in response to attack by plant-pathogenic bacteria

Abstract

The natural resistance of plants to disease is based not only on preformed mechanisms, but also on induced mechanisms. The defense mechanisms present in resistant plants may also be found in susceptible ones. This study attempted to analyze the metabolic alterations in plants of the potato Solanum tuberosum L. cv. Agata that were inoculated with the incompatible plant-pathogenic bacteria X. axonopodis and R. solanacearum, and the compatible bacterium E. carotovora. Levels of total phenolic compounds, including the flavonoid group, and the activities of polyphenol oxidase (PPO) and peroxidase (POX) were evaluated. Bacteria compatibility was evaluated by means of infiltration of tubers. The defense response was evaluated in the leaves of the potato plants. Leaves were inoculated depending on their number and location on the stem. Multiple-leaf inoculation was carried out on basal, intermediate, and apical leaves, and single inoculations on intermediate leaves. Leaves inoculated with X. axonopodis and with R. solanacearum showed hypersensitive responses within 24 hours post-inoculation, whereas leaves inoculated with E. carotovora showed disease symptoms. Therefore, the R. solanacearum isolate used in the experiments did not exhibit virulence to this potato cultivar. Regardless of the bacterial treatments, the basal leaves showed higher PPO and POX activities and lower levels of total phenolic compounds and flavonoids, compared to the apical leaves. However, basal and intermediate leaves inoculated with R. solanacearum and X. axonopodis showed increases in total phenolic compounds and flavonoid levels. In general, multiple-leaf inoculation showed the highest levels of total phenolics and flavonoids, whereas the single inoculations resulted in the highest increase in PPO activity. The POX activity showed no significant difference between single-and multiple-leaf inoculations. Plants inoculated with E. carotovora showed no significant increase in defense mechanisms such as enzyme activity and phenolic compounds. Therefore, resistance or susceptibility in S. tuberosum cv. Agata might depend on leaf age, type of inoculation performed (single or multiple), and the interaction between plant and pathogen.

Spatial and temporal dynamics of primary and secondary metabolism in Phaseolus vulgaris challenged by Pseudomonas syringae

“…Upon infection with P. syringae, transcripts encoding components of the shikimate and phenylpropanoid biosynthesis pathways are induced in the host plant (Truman et al 2006). Solanum lycopersicum infected with Pto accumulates phenylpropanoids and flavonoids (Poiatti et al 2009, López-Gresa et al 2010, some of them showing antimicrobial activity (Vargas et al 2011).…”

Secondary metabolism in micropropagated Hypericum perforatum L. grown in non-aerated liquid medium

“…Extracts were filtered and centrifuged at 1,2509g for 15 min. Total phenolic compounds were analyzed in the supernatant by a colorimetric method as described previously (Poiatti et al 2009). Briefly, 100 lL of extract was mixed with 2.5 mL Folin-Ciocaulteau reagent (ImprintSul Ltda, Brazil) and 0.7 M Na 2 CO 3 .…”

“…Extracts were filtered and centrifuged at 2,5009g for 15 min at 5°C, and the supernatant was collected for determination of protein content and enzyme assay. PPO activity was determined using chlorogenic acid as the substrate at 400 nm in a spectrophotometer, according to Poiatti et al (2009). Specific enzyme activity was defined as the change in absorbance min -1 mg -1 protein.…”

Evidence that Cell Death is Associated with Zebra Chip Disease in Potato Tubers

“…The other form of potato tissue browning ('enzymatic') involves polyphenol oxidase enzymes (EC 1.14.18.1 and EC 1.10.3.2) (PPOs), which act in disease resistance, mechanical damage and wounding by catalyzing o-hydroxylation of monophenols to o-diphenols. They can further catalyse the oxidation of o-diphenols to o-quinones, which can rapidly undergo polymerisation to form polyphenols (pigmented compounds), which are deposited at the site of infection and are often more toxic to the pathogen than the original parent phenolic (Pendharkar and Nair 1995;Friedman 1997;Lulai and Corsini 1998;Gandia-Herrero et al 2005;Poiatti et al 2009). Whether the altered reducing sugar and/or phenolic content found in tubers from ZC-affected plants have anything to do with the characteristic striping and/or "necrotic flecking" found in tubers from ZC-affected plants has yet to be determined.…”