Trehalose and trehalase in root nodules of Medicago truncatula and Phaseolus vulgaris in response to salt stress.

Trehalose (alpha-D-glucopyranosyl-1,1-alpha-D-glucopyranoside), a non-reducing disaccharide, has been found in a wide variety of organisms playing an important role as an abiotic stress protectant. Plants may come into contact with trehalose from exogenous sources, such as in plant-rhizobia symbiosis in which the rhizobia have the capacity to produce trehalose. The aim of this work is to analyse how trehalose and trehalase respond to salt stress in root nodules of legumes. For this purpose, tissue expression of Medicago truncatula trehalase gene (MTTRE1) and the expression of MTTRE1 under salt stress were analysed by real-time quantitative reverse transcription-PCR method. Trehalase activity was determined and trehalose was also measured by gas chromatography. In addition, trehalase protein occurrence in different organs and at different developmental stages in Phaseolus vulgaris plants has been studied. MTTRE1 expression is induced in nodules compared with leaves and roots, indicating a transcriptional regulation of trehalase in the presence of the microsymbiont. Under salt stress conditions, trehalase activity is downregulated at the transcriptional level, allowing trehalose accumulation. The results found in this study led us to conclude that trehalase activity is induced in root nodules of legumes by the microsymbiont and that under salt stress conditions; trehalase activity is downregulated at the transcriptional level in M. truncatula nodules. This allows trehalose accumulation and supports the possible role of this disaccharide as a stabilizer against salt stress conditions.