Fungi plant defences

Many studies show that AM fungi initiate a host defence response which is subsequently suppressed (Lambais and Mehdy, 1993 Volpin et al. 1994, 1995). The decreases were accompanied by differential reductions in the levels of mRNAs encoding for different endochitinase and endoglucanase isoforms. But the activation of specific plant defence reactions by AM fungi could predispose the plant to an early response to attack by a root pathogen (Gianinazzi-Pearson et al., 1994). 

Pozo M.J., Cordier C., Dumas-Gaudot E., Gianinazzi S., Barea J.M., Azcon-Aguilar C. Localized versus systemic effect of arbuscular mycorrhizal fungi on defence responses to Phytophthora infection in tomato plants. J... 

Terpenes are secondary metabolites synthesized mainly by plants, but also by a limited number of insects, marine micro-organisms and fungi. These corrpounds were first considered as waste products from plant metabolism with no specific biological role, but later, the involvement of some terpenes as intermediates in relevant biosynthetic processes was discovered [1]. Additionally, it has been well demonstrated that many terpenes play important ecological roles [1] as in plant defence, for example as insect repellents, and in symbiotic mechanisms, for example as attractants to specific insect species to stimulate cross pollination. 

Systemic Acquired Resistance. SAR is the induction of a transient long-distance (translocated) defence response to fungal attack that is distinct from the local production of phytoalexins. The transient nature of SAR is important and has likely been selected in the course of evolution as a corollary to the energy demands that are made on the plant by the permanent mobilisation of resistance mechanisms. However, plants challenged by fungi are sensitised to subsequent attack and the speed of their SAR response is increased. 

Psoralens (furocoumarins used by some plants in defence from insects and fungi) photoreact with ds DNA to form interstrand crosslinks in the presence of near-UV light by two steps intercalation in the dark and formation of monoadducts or interstrand crosslinks (Song and Tapley, 1979). This reaction has the advantage that psoralen binds, in contrast to photobiotin, only to nucleic acid. 

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