Comparing the transcriptomes of TPS1 transgenic and wild type potato plants (CBX76). unidentified

Potato plants expressing the trehalose-6-phosphate synthase (TPS1) gene of yeast are improved in drought tolerance. TPS1-transgenic derivatives of the cultivar White Lady, however, grow slower and have a reduced carbon fixation and stomatal density than the wild-type, even under non stress conditions. To understand the molecular basis of this phenomenon, we have compared the transcriptomes of wild-type and TPS1-transgenic (line T2) plants grown under optimal condition, using the POCI microarray. Two independently grown biological repeats were used. Of each biological repeats three technical repeat microarray hybridisations were performed. 63 and 163 genes were up- or down-regulated more than two-fold, respectively, in the leaves of TPS1-transgenic plants compared to the wild-type. Using the MapMan software, these genes were assigned into functional groups. This assignment and an extensive literature search revealed that about half of the known genes can be connected to three major areas: carbon fixation and metabolism, stress, and regulatory functions. According to the literature, the majority of the genes in the carbon fixation and metabolism group are known to be regulated by light and the circadian clock. Members of the second group are regulated by biotic and/or abiotic stresses or by factors, such as hormones and reactive oxygen species, which are involved in stress related regulatory cascades. Genes with regulatory function include transcription factors and other proteins, which are involved in signalling cascades or in different transcriptional and translational regulatory mechanisms. To verify the microarray results, we used RNA gel blot analysis to examine the expression of eight genes and found that RNA gel blot and microarray data were correlated in each case.