Trehalose metabolism in wheat and identification of trehalose metabolizing enzymes under abiotic stress conditions

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Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Gıda Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2003

Öğrenci: TAREK EL-BASHİTİ

Danışman: HALUK HAMAMCI

Özet:

Trehalose (a-D-glucopyranosyl-1,1-a-D-glucopyranoside) is a non reducing disaccharide of glucose that occurs in a large variety of organisms, ranging from bacteria to invertebrate animals, where it serves as an energy source or stress protectant. Until recently, only few plant species, mainly desiccation tolerant ءresurrection̕ plants, were considered to synthesize trehalose. Although most plant species do not appear to accumulate easily detectable amounts of trehalose, the discovery of genes for trehalose biosynthesis in Arabidopsis and in a range of crop plants suggests that the ability to synthesize trehalose is widely distributed in the plant kingdom. In this study, three wheat cultivars (Triticum aestivum L.) Tosun, Bolal (stress tolerant) and Çakmak (stress sensitive) were analysed for the presence of trehalose. Using gas chromatography-mass spectrometry (GC-MS) analysis, trehalose was unambiguously identified in extracts from seeds and seedlings of three different wheat cultivars (Bolal, Tosun and Çakmak). The trehalose amount was quantified by high performance liquid chromatography connected with refractory index detector. Effects of drought and salt stress on trehalose contents of wheat cultivars were studied at seedling level and trehalose analysis was achieved both on shoot and root tissues. It was found that trehalose had accumulated under salt and drought stress conditions in all wheat cultivars. The highest trehalose accumulation was detected in roots of Bolal cultivar under drought stress condition. Furthermore, trehalose metabolizing enzymes; trehalose-6-phosphate synthase (TPS) and trehalase enzyme activities were measured in roots and shoots of Bolal and Çakmak cultivars under control, salt and drought stress conditions. The most interesting results that we found that TPS activity sharply increased under stress conditions. The activity of TPS in