Over-time changes in the plant transcriptomic profile during the incompatible interaction of Mi-1-gene-carrying tomato with the whitefly Bemisia tabaci

Plant resistance is one of the essential tools for the development of Integrated Pest Management (IPM) programmes. In tomato cultivation, the whitefly Bemisia tabaci is one of the major pests, causing both direct and indirect damage. So far, the Mi-1 gene is the only one with the capacity to confer resistance not only to B. tabaci but also to other insects and nematodes; thus, it deserves a detailed investigation of its function. In this work, gene expression was studied during the incompatible interaction of B. tabaci with plants carrying the Mi-1 gene, using the oligonucleotide microarray technique (GeneChip® Tomato Genome Array from Affymetrix®). For this purpose, leaflets of resistant plants (cv. Motelle) were sampled and analysed at 2 and 12 days post infestation (dpi) with adult insects, and the transcriptomic profile was compared to that of other uninfested plants of the same age.

At the early phase (2 dpi), 159 transcripts were significantly more expressed in the infested plants than in the uninfested ones; meanwhile, 189 transcripts were repressed. Transcriptional reprogramming was most intense later, at 12 dpi, as 595 transcripts were overexpressed and 437 were repressed. Only 44 upregulated and 68 downregulated transcripts were common at both time points (2 and 12 dpi). The Mapman categories with most differential transcripts were those that include genes with unknown function or that are in the miscellaneous group. However, relevant differential gene expression was also observed in the categories RNA, protein, signalling, cell wall, hormone metabolism and biotic and abiotic stress. These results provide important information about genes related to the resistance conferred by the Mi-1 gene against the attack of adults and nymphs of B. tabaci and whose role deserves further investigation.