Involvement of Parasitism Proteins in Plant Nematode and Opportunistic Fungi Connections

Nematodes and fungi are known to cause widespread destruction in major crops and hence create significant economic loss. Various parasitic mechanisms have evolved in different species, where the parasitism proteins have a big role to play. The majority of Avr genes in fungi are thought to produce effectors that promote virulence by inhibiting immunity activated by pathogen-associated molecular patterns (PAMP) and inducing effector-triggered immunity (ETI) in plants with appropriate resistance proteins. These cognate resistance proteins recognise the effector molecules directly or indirectly, that are found on the plasma membrane or within the plant cell. In case of indirect recognition, it is hypothesised that the virulence target of a host effector is guarded by a resistance protein. Thus, any modification of the host when detected activates effector-triggered immunity. On the other hand, toxins also play a significant role in determining specificity in some plant–fungus interactions. In this case, susceptibility to the toxins or resistance to the fungus are always correlated and are important during the fungal pathogenesis on a particular host. Also, nematodes deploy an array of proteins to parasitize plant tissues. This includes cell wall modifying enzymes, regulators of host cell processes, plant molecule mimics, and new parasitism proteins. These may inhibit host defences by localising to the nucleus of the plant cell. Different omics approaches, protein–protein interaction assays, RNA-mediated interference analysis, and phenotypic changes in transformed plant tissues are used to unravel biological roles of these putative genes which can become instrumental in building transgenic resistance in crops.