PROPAGATION AND FIELD TRIAL OF TRANSGENIC PERSIMMON ROOTSTOCKS WITH THE GENE FOR COMPATIBLE SOLUTE BIOSYNTHESIS

许多生物体，包括某些植物，积累了对新陈代谢没有抑制作用的低分子量的水溶性有机化合物。这些化合物被称为相容性溶质，不仅通过调节细胞中的渗透压，而且通过稳定复杂蛋白质的四级结构，使它们能够耐受某些类型的环境压力。近年来的研究表明，通过基因工程技术合成相容性溶质，可以提高植物对环境胁迫的耐受性。然而，所有这些研究都涉及草本植物物种。我们选择了日本柿（柿），这是在日本的主要水果作物之一，易受盐和干旱胁迫的损害，作为候选人的第一个木本植物物种的基因工程的耐受环境压力，通过转化的基因参与兼容溶质。将球形节杆菌胆碱氧化酶基因和苹果山梨醇-6-磷酸脱氢酶基因的嵌合基因分别整合到柿子基因组中，使其产生甜菜碱和山梨醇。通过测定NaCl胁迫下叶片叶绿素荧光的最大值（Fm）与可变值（Fv）的比值，研究了转化柿的耐盐性。NaCl胁迫下，转甜菜碱或山梨醇基因柿的Fv/Fm下降速率低于对照转化和非转化株系。对转基因柿作为砧木的可能性进行了试验。

Many organisms, including certain plants, accumulate water-soluble organic compounds of low molecular weight that have no inhibitory effects on metabolism. These compounds are referred to as compatible solutes and allow them to tolerate certain types of environmental stress not only by adjusting osmotic pressure in cells but also by stabilizing the quaternary structures of complex proteins. Recent studies have shown that enhancement of tolerance to environmental stresses in plants can be achieved by genetic engineering of the biosynthesis of compatible solutes. All these studies, however, deal with herbaceous plant species. We selected Japanese persimmon (Diospyros kaki), which is one of the major fruit crops in Japan and susceptible to damage from salt and drought stresses, as a candidate for the first woody plant species to be genetically engineered for tolerance to environmental stress by transforming the genes involved in compatible solutes. Chimeric genes constructed from the choline oxidase gene of Arhrobacter globiformis and the cDNA for sorbitol-6-phosphate dehydrogenase of apple (Malus x domestica) were integrated into the persimmon genome to confer the ability to produce glycinebetaine and sorbitol, respectively. Tolerance to salt stress of transformed persimmon plants were determined by measuring the ratio of the variable (Fv) to the maximum (Fm) fluorescence of chlorophyll in leaves under NaCl stress. The rate of decline in Fv/Fm under NaCl stress was lower in transgenic persimmon plants producing glycinebetaine or sorbitol than control transformed and non-transformed lines. The possibility of using these transgenic persimmon as a rootstock was tested.