Microarray analysis of salicylic acid- and jasmonic acid-signalling in responses of Nicotiana attenuata to attack by insects from multiple feeding guilds
Resistance to herbivore attack is elicited by damage- and herbivore-specific signals. To understand the role of salicylic acid (SA) and jasmonic acid (JA) signalling in the herbivore-induced transcriptional responses of the native tobacco Nicotiana attenuata, a comparison was made of the responses in undamaged systemic leaves after attack by five herbivore species (Manduca sexta, Spodoptera littoralis, Trichoplusia ni, Tupiocoris notatus and Myzus nicotianae) from three feeding guilds and to elicitation by SA, BTH and methyl-JA with a 789-gene oligo-microarray and measured endogenous SA and JA levels. Systemic responses to M. sexta attack were similar to the responses in locally attacked tissues; however, the up-regulation of genes (such as proteinase inhibitor, PI) was more attenuated and resembled the responses to attack from the other Lepidopteran, S. littoralis, and to methyl-JA elicitation. Responses to attack from the puncture-feeding T. notatus repressed some JA-elicited genes (PI) elicited by the leaf-chewing Lepidopterans and most closely resembled SA elicitation. Attack from the phloem-feeding M. nicotianae aphids elicited few responses. Treatment with the SA-mimic BTH induced both SA- and JA-elicited genes and most closely resembled the aphid response. SA concentrations were uniformly increased by herbivore attack and correlated with the down-regulation of photosynthetic genes in all treatments.