Plant defence ecdysteroids

Recently, it has been demonstrated that ecdysteroid accumulation in spinach is inducible by mechanical [50] or insect [51] damage to roots. Evidence was further provided for the involvement of jasmonates in the induction of de novo ecdysteroid synthesis. Also, short- and long-term labelling of 20E from [2-14C]mevalonic acid in spinach demonstrate that ecdysteroids are metabolically stable in this species, which fits much better with a role in plant defence, rather than a phytohormonal role [52], Most recently, it has been demonstrated that root predation by the fungus gnat Bradysia impatiens results in elevated ecdysteroid levels in spinach and a significant reduction in larval establishment of B. impatiens [53],... 

Two main hypotheses have been put forward to account for the occurrence of ecdysteroids in the plant world. The first is that PEs have a hormonal role within the plant, but there is very little hard evidence in support of this hypothesis (reviewed in [26]). Alternatively, PEs participate in the defence of plants against non-adapted phytophagous invertebrates. Deterrent effects of 20E on non-adapted insect species are... 

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