Gojło Ewa, Pupel Piotr, Lahuta Lesław B, Podliński Paweł, Kucewicz Magdalena, Górecki Ryszard J
University of Warmia and Mazury in Olsztyn, Department of Plant Physiology, Genetics and Biotechnology, ul. Oczapowskiego 1A/132, 10-719 Olsztyn, Poland.
Department of Botany and Nature Protection, University of Warmia and Mazury, Plac Łódzki 1, 10-718 Olsztyn, Poland.
J Plant Physiol. 2015 Jul 20;184:37-48. doi: 10.1016/j.jplph.2015.06.013. Epub 2015 Jul 14.
Galactinol is the galactosyl donor for the biosynthesis of both the raffinose family oligosaccharides (RFOs) and galactosyl cyclitols (Gal-C). Its synthesis by galactinol synthase (GolS, EC 2.4.1.123) is the first committed step of the soluble α-D-galactosides biosynthetic pathway in orthodox seeds. The deposition of galactosides in seeds is suggested to be associated with desiccation tolerance (DT). In this work, for the first time, we cloned and characterized two Vicia hirsuta (L.) S.F. Gray galactinol synthase genes (VhGolS1, VhGolS2), analyzed galactinol synthase activity and measured the accumulation of galactosides of both sucrose and D-pinitol in relation to the acquisition of DT in developing seeds of this wild species. A developmentally induced increase of VhGolS1 expression preceded the rise of GolS activity in crude protein extract from maturing seeds, while the expression of the VhGolS2 gene remained low. GolS activity peaked just after the beginning of the maturation drying phase. The increase of GolS activity was not followed by galactinol accumulation, instead the high enzyme activity was related to high levels of galactose bound in soluble galactosides of the RFO and galactosyl pinitol series. Acquisition of DT coincided with an increase of VhGolS1 expression, high galactinol synthase activity and the accumulation of oligogalactosides in seeds. DT was positively correlated with the high content of soluble α-D-galactosides of both the RFO and galactosyl pinitol series as well as with the amount of galactose bound in these galactosides.
棉子糖是棉子糖家族寡糖（RFOs）和半乳糖基环醇（Gal-C）生物合成的半乳糖基供体。棉子糖合成酶（GolS，EC 2.4.1.123）催化其合成，这是正统种子中可溶性α-D-半乳糖苷生物合成途径的首个关键步骤。种子中半乳糖苷的积累被认为与耐旱性（DT）有关。在本研究中，我们首次克隆并鉴定了两个硬毛野豌豆（Vicia hirsuta (L.) S.F. Gray）棉子糖合成酶基因（VhGolS1、VhGolS2），分析了棉子糖合成酶活性，并测定了该野生物种发育种子中蔗糖和D-松醇半乳糖苷的积累与耐旱性获得之间的关系。VhGolS1表达的发育诱导增加先于成熟种子粗蛋白提取物中GolS活性的升高，而VhGolS2基因的表达则保持在较低水平。GolS活性在成熟干燥阶段开始后不久达到峰值。GolS活性增加后并未伴随棉子糖积累，相反，高酶活性与RFO和半乳糖基松醇系列可溶性半乳糖苷中结合的高水平半乳糖有关。耐旱性的获得与VhGolS1表达增加、高棉子糖合成酶活性以及种子中低聚半乳糖苷的积累同时发生。耐旱性与RFO和半乳糖基松醇系列可溶性α-D-半乳糖苷的高含量以及这些半乳糖苷中结合的半乳糖量呈正相关。
