Molecular interactions between the specialist herbivore Manduca sexta (Lepidoptera, Sphingidae) and its natural host Nicotiana attenuata. I. Large-scale changes in the accumulation of growth- and defense-related plant mRNAs

Plants respond to herbivore attack with a dramatic functional reorganizatio n that involves the activation of direct and indirect defenses and toleranc e, which in turn make large demands on primary metabolism. Here we provide the first characterization of the transcriptional reorganization that occur s after insect attack in a model plant-herbivore system: Nicotiana attenuat a Torr, ex Wats.-Manduca sexta. We used mRNA differential display to charac terize one-twentieth of the insect-responsive transcriptome of N. attenuata and verified differential expression for 27 cDNAs. Northern analyses were used to study the effects of folivory and exposure to airborne methyl jasmo nate and for kinetic analyses throughout a 16-h-light/8-h-dark cycle. Seque nce similarity searches allowed putative functions to be assigned to 15 tra nscripts. Genes were related to photosynthesis, electron transport, cytoske leton, carbon and nitrogen metabolism, signaling, and a group responding to stress, wounding, or invasion of pathogens. Overall, transcripts involved in photosynthesis were strongly down-regulated, whereas those responding to stress, wounding, and pathogens and involved in shifting carbon and nitrog en to defense were strongly up-regulated. The majority of transcripts respo nded similarly to airborne methyl jasmonate and folivory, and had tissue- a nd diurnal-specific patterns of expression. Transcripts encoding Thr deamin ase (TD) and a putative retrotransposon were absent in control plants, but were strongly induced after herbivory. Full-length sequences were obtained for TD and the pathogen-inducible alpha -dioxygenase, PIOX. Effects of abio tic and biotic stimuli were investigated for transcripts encoding TD, impor tin alpha, PIOX, and a GAL8S-like kinase cofactor.