Jasmonate is essential for insect defense in  Arabidopsis

Abstract

The signaling pathways that allow plants to mount defenses against chewing insects are known to be complex. To investigate the role of jasmonate in wound signaling in Arabidopsis and to test whether parallel or redundant pathways exist for insect defense, we have studied a mutant (fad3-2 fad7-2 fad8) that is deficient in the jasmonate precursor linolenic acid. Mutant plants contained negligible levels of jasmonate and showed extremely high mortality (Ϸ80%) from attack by larvae of a common saprophagous fungal gnat, Bradysia impatiens (Diptera: Sciaridae), even though neighboring wild-type plants were largely unaffected. Application of exogenous methyl jasmonate substantially protected the mutant plants and reduced mortality to Ϸ12%. These experiments precisely define the role of jasmonate as being essential for the induction of biologically effective defense in this plant-insect interaction. The transcripts of three wound-responsive genes were shown not to be induced by wounding of mutant plants but the same transcripts could be induced by application of methyl jasmonate. By contrast, measurements of transcript levels for a gene encoding glutathione S-transferase demonstrated that wound induction of this gene is independent of jasmonate synthesis. These results indicate that the mutant will be a good genetic model for testing the practical effectiveness of candidate defense genes.

Salicylic acid-independent plant defence pathways

“…Depending on the type of invader encountered, the plant appears to be capable of switching on the appropriate pathway or combination of pathways. The plant signalling molecules salicylic acid, jasmonic acid and ethylene play an important role in this signalling network: blocking the response to either of these signals can render plants more susceptible to pathogens and even insects 6, [49][50][51][52] . Resistance conferred by the salicylic acid-dependent pathway might be directed more against certain types of pathogens, whereas resistance conferred by salicylic acid-independent pathways might operate more effectively against other types of pathogens.…”

Genetic admixture and heterosis may enhance the invasiveness of common ragweed

“…Moreover, after removal from the bench, the plants were sprayed with 5 mM methyl jasmonate until all leaves were soaked and left to dry before they were moved back. Methyl jasmonate is commonly used to elicit defense responses against herbivores in many plant species (McConn, Creelman, Bell, Mullet, & Browse, 1997). The watering regime was similar to the control plants.…”

On plant defense signaling networks and early land plant evolution

“…Furthermore, SA is involved in the induction of HR, resulting in plant cell death [109]. On the other hand, JA is produced in response to herbivores, which induce wounding [110]. In concert with ET, JA also regulates responses towards several necrotrophic pathogens, i.e.…”