Interaction of Extracellular Proteinases of Phytophthora cinnamomi with Proteinase Inhibitors Produced by Avocado Root

Identification of Theobroma cacao genes differentially expressed during Phytophthora megakarya infection

“…Those genes encode chitinase (PR-3, 8 and 11), osmotin (PR-5), peroxidase (PR-9), cytochrome P450, or transcription factors. In avocado plants, infection by Phytophthora cinnamomi induces proteinase inhibitors (PR-6), which block the pathogen's extracellular proteases [17].…”

Advances in Understanding Defense Mechanisms in Persea americana Against Phytophthora cinnamomi

“…At around 12-18 hpi the amplitude of the SA defense response decreases significantly (van den Berg et al, 2018b), thereby reducing NPR1 activation and consequent suppression of the JA/ET pathway. In Dusa®, at 18 hpi, the expression of two genes encoding for proteinase inhibitors, which counter extracellular P. cinnamomi proteinases (Encino-López et al, 2011), was significantly upregulated and linked to increased resistance to P. cinnamomi. Furthermore, the expression of two genes involved in cell wall modification, profilin, and mlo, are also significantly upregulated in Dusa® at 18 hpi (Mahomed and van den Berg, 2011).…”

“…An increase in peroxidase activity was also reported at 96 hpi but was not involved in lignin accumulation but rather contributed to H 2 O 2 accumulation. Furthermore, the susceptible avocado response was marked with a decline in epicatechin and total phenolics production while no changes in procyanidins were observed (García-Pineda et al, 2010;Encino-López et al, 2011). A decline in epicatechin caused a lower redox state, thereby reducing the plant's ability to scavenge ROS, further triggering cell death and rootstock susceptibility.…”

“…Proteinases are produced by pathogens to intensify the disease and in response plants produce proteinase inhibitors which counter these catalytic enzymes. A study was conducted to assess the role of avocado proteinase inhibitors against extracellular proteinases produced by P. cinnamomi (Encino-López et al, 2011). Proteinase inhibitors were extracted from a susceptible rootstock at various time-points following P. cinnamomi inoculation; a 35% increase in inhibitory activity was recorded for root extracts taken 4 dpi and a significant decrease in root colonization was observed when roots were treated with the avocado proteinase inhibitor.…”

“…However, even though the proteinase inhibitors present in the susceptible rootstock at 4 dpi were effective at limiting root colonization, the production of these inhibitors may simply be too late to contribute to a successful defense response against P. cinnamomi. We hypothesize that the delivery of proteinase inhibitors by avocado may suppress the enzymatic activity of P. cinnamomi extracellular proteinases when released in a timeous manner (Encino-López et al, 2011). Assessing the temporal regulation of avocado proteinase inhibitor genes along with assays to determine the effectiveness of the inhibitors, from a range of rootstocks with varying levels of P. cinnamomi resistance/ susceptibility, would be required to fully uncover their importance.…”