Abstract
The interaction avocado plant/Phytophtora cinnamomi has not been explored at the level of defense responses induced by this pathogen. Here, we show that the infection of avocado plants by Phytophthora cinnamomi induced proteinase inhibitor, which had inhibitor activity against extracellular proteases of P. cinnamomi. Extracellular proteinase activity was not increased with the addition of the avocado root cell wall to liquid culture but decreased in the presence of root of healthy avocado plants. The pretreatment of avocado roots with the avocado inhibitor before the infection by P. cinnamomi inhibited root colonization by the pathogen. Avocado inhibitor had no effect on in vitro growth of the oomycete, suggesting that the inhibition of root colonization could be due to its interaction with pathogen proteinases.
Highlights
Most plants are resistant to most microbes and only specialist organisms have evolved the capacity to overcome plant defenses
Because only a few works of biochemical responses have been done on avocado roots infected with P. cinnamomi, to know how this plant regulates the biochemical battery of defense responses in the presence of the pathogen, we explore the role of proteinases during this interaction
After 4 days of infection with P. cinnamomi, proteinase inhibitor activity was observed to increase in avocado roots
Summary
Most plants are resistant to most microbes and only specialist organisms have evolved the capacity to overcome plant defenses. Mechanisms of resistance in plants can be subdivided into two categories, passive (constitutive) and active (induced). Passive mechanisms involve both structural elements, such as the cuticle and pre-formed antimicrobial chemical compounds within the plant termed phytoanticipins. These form the initial layers of protection against microbial attack. Oomycetes form a diverse group of fungus-like eukaryotic microorganisms that includes both saprophytes and pathogens of plants. They cause devastating diseases in numerous crop, ornamental, and native plants. Oomycetes are known to secrete a range of degradative enzymes [3], but there is only limited direct demonstration of the role of cell wall-degrading enzymes in plant penetration by oomycete pathogens
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