Soil drench treatment with ß-aminobutyric acid increases drought tolerance of potato.

The non-protein amino acid ß-aminobutyric acid (BABA) is known to be a priming agent for a more efficient activation of cellular defence responses and a potent inducer of resistance against biotic and abiotic stresses in plants. Nevertheless, most of the studies on priming have been carried out in Arabidopsis. In potato, the effect of BABA was demonstrated only on biotic stress tolerance. We investigated the effect of BABA on the drought tolerance of potato and found that soil drenched with BABA at a final concentration of 0.3 mM improves the drought tolerance of potato. Water loss from the leaves of the primed plants is attenuated and the yield is increased compared to the unprimed drought-stressed plants. The metabolite composition of the tubers of the BABA-treated plants is less affected by drought than the tuber composition of the non-treated plants. Nitric oxide and ROS (reactive oxygen species) production is increased in the BABA-treated roots but not in the leaves. In the leaves of the BABA-treated plants, the expression of the drought-inducible gene StDS2 is delayed, but the expression of ETR1, encoding an ethylene receptor, is maintained for a longer period under the drought conditions than in the leaves of the non-treated, drought-stressed control plants. This result suggests that the ethylene-inducible gene expression remains suppressed in primed plants leading to a longer leaf life and increased tuber yield compared to the non-treated, drought-stressed plants. The priming effect of BABA in potato, however, is transient and reverts to an unprimed state within a few weeks.

Effects of yeast trehalose-6-phosphate synthase 1 on gene expression and carbohydrate contents of potato leaves under drought stress conditions.

BACKGROUND: The development of drought-tolerant, elite varieties of potato (Solanum tuberosum L.) is a challenging task, which might be achieved by introducing transgenic lines into breeding. We previously demonstrated that strains of the White Lady potato cultivar that express the yeast trehalose-6-phosphate synthase (TPS1) gene exhibit improved drought tolerance. RESULTS: We investigated the responses of the drought-sensitive potato cultivar White Lady and the drought-tolerant TPS1 transgenic variant to prolonged drought stress at both the transcriptional and metabolic levels. Leaf mRNA expression profiles were compared using the POCI microarray, which contains 42,034 potato unigene probes. We identified 379 genes of known function that showed at least a 2-fold change in expression across genotypes, stress levels or the interaction between these factors. Wild-type leaves had twice as many genes with altered expression in response to stress than TPS1 transgenic leaves, but 112 genes were differentially expressed in both strains. We identified 42 transcription factor genes with altered expression, of which four were uniquely up-regulated in TPS1 transgenic leaves. The majority of the genes with altered expression that have been implicated in photosynthesis and carbohydrate metabolism were down-regulated in both the wild-type and TPS1 transgenic plants. In agreement with this finding, the starch concentration of the stressed leaves was very low. At the metabolic level, the contents of fructose, galactose and glucose were increased and decreased in the wild-type and TPS1 transgenic leaves, respectively, while the amounts of proline, inositol and raffinose were highly increased in both the wild-type and TPS1 transgenic leaves under drought conditions. CONCLUSIONS: To our knowledge, this study is the most extensive transcriptional and metabolic analysis of a transgenic, drought-tolerant potato line. We identified four genes that were previously reported as drought-responsive in non-transgenic Andean potato cultivars. The substantial increases in proline, inositol and raffinose contents detected in both the wild-type and TPS1 transgenic leaves appears to be a general response of potatoes to drought stress. The four transcription factors uniquely up-regulated in TPS1 transgenic leaves are good candidates for future functional analyses aimed at understanding the regulation of the 57 genes with differential expression in TPS1 transgenic leaves.

Interaction between SNF1-related kinases and a cytosolic pyruvate kinase of potato.

SNF1-related protein kinases (SnRKs) are widely conserved in plants. Previous studies have shown that members of the SnRK1 subfamily phosphorylate and inactivate at least four important plant metabolic enzymes: 3-hydroxy-3-methylglutaryl-CoA reductase, sucrose phosphate synthase, nitrate reductase, and trehalose phosphate synthase 5. In this paper, we demonstrate that two SnRK1 proteins of potato, PKIN1 and StubSNF1, interact with a cytosolic pyruvate kinase (PK(c)) of potato in a yeast two-hybrid assay. The interacting domain of PK(c) is located in its C-terminal region and contains the putative SnRK1 recognition motif ALHRIGS(500)ASVI. Our results indicate that both SnRK1s influence PK(c) activity in vivo. Antisense repression of SnRK1s alters the intensity and light/dark periodicity of PK activity in leaves. However, the differences between PK activity curves in antisense PKIN1 and antisense StubSNF1 lines indicated that the function of the two kinases is not identical in potato.