Overlapping sets of transcripts from host and non-host interactions of tomato are expressed early during non-host resistance

Natural immunity present in all the plants against most of the pathogens is called as non-host resistance (NHR). Although NHR is most durable form of resistance, it was less studied compared to other forms of resistance. We compared transcriptional changes in tomato during non-host (Magnaporthe grisea) and compatible (Alternaria alternata f. sp. lycopersici) interactions using Agilent microarray GeneChip containing ∼44,000 probe sets. The experiment was designed to understand the early and late responses of tomato leaves inoculated with non-host and compatible pathogens. Microarray data revealed that the expression profiles in the nonhost and compatible interactions at 6 h post inoculation (hpi) and 24 hpi largely overlapped indicating that a set of genes are activated during plant-pathogen interaction. However, these genes were expressed much earlier in NHR compared to a compatible interaction. NHR is, therefore, an accelerated and amplified basal defense response. Transcripts involved in energy production (carbohydrate metabolism and photosynthesis) were down-regulated, whereas transcripts associated with catabolic processes (starch and sucrose hydrolysis) were up-regulated in both the interactions at 6 and 24 hpi. We have also identified that the pathway involved in synthesis of volatile compounds like 2-phenylethanol was induced during NHR in tomato. This is the first report of transcriptome profile in tomato during non-host interactions against M. grisea.