Bemisia tabaci B and Q biotypes thermotolerance

The whitefly Bemisia tabaci (Gennadius) causes tremendous losses to agriculture by direct feeding on plants and by vectoring several families of plant viruses. The B. tabaci species complex comprises over 10 genetic groups (biotypes) that are well defined by DNA markers and biological characteristics. B and Q are amongst the most dominant and damaging biotypes, differing considerably in fecundity, host range, insecticide resistance, virus vectoriality, and the symbiotic bacteria they harbor. We used a spotted B. tabaci cDNA microarray to compare the expression patterns of 6,000 ESTs of B and Q biotypes under standard 25°C regime and heat stress at 40°C. Overall, the number of genes affected by increasing temperature in the two biotypes was similar. Gene expression under 25ºC normal rearing temperature showed clear differences between the two biotypes: B exhibited higher expression of mitochondrial genes, and lower cytoskeleton, heat-shock and stress-related genes, compared to Q. Exposing B-biotype whiteflies to heat stress was accompanied by rapid alteration of gene expression. For the first time, the results here present differences in gene expression between very closely related and sympatric B. tabaci biotypes, and suggest that these clear-cut differences are due to better adaptation of one biotype over another and might eventually lead to changes in the local and global distribution of both biotypes. 3 replicates comparing Q biotype under 40 degrees celsius (C) with three replicates under 25 C. The same number of replicates comparing B biotype under 40 C and 25 C, and three replicates comparing B and Q biotypes under 25 C.