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

许多生物，包括某些植物，积累低分子量的水溶性有机化合物，对新陈代谢没有抑制作用。这些化合物被称为相容溶质，它们不仅通过调节细胞内的渗透压，而且通过稳定复杂蛋白质的四级结构，使它们能够承受某些类型的环境压力。最近的研究表明，植物对环境胁迫的耐受性可以通过生物合成相容溶质的基因工程来实现。然而，所有这些研究都涉及草本植物物种。作为日本主要水果作物之一的柿子（Diospyros kaki）易受盐和干旱胁迫的损害，我们选择了它作为第一个通过转化与相容溶质相关的基因来耐受环境胁迫的木本植物物种。将球状Arhrobacter globiformis胆碱氧化酶基因和苹果（Malus x domestica）山梨糖醇-6-磷酸脱氢酶cDNA构建的嵌合基因整合到柿子基因组中，分别获得了生产甘氨酸甜菜碱和山梨糖醇的能力。通过测定NaCl胁迫下叶片叶绿素可变荧光（Fv）与最大荧光（Fm）的比值，确定转化柿植株对盐胁迫的耐受性。产生甘氨酸甜菜碱和山梨糖醇的转基因柿子植株在NaCl胁迫下Fv/Fm的下降速率低于对照转化系和未转化系。试验了这些转基因柿子作为砧木的可能性。

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.