Abstract: Through a similarity-based cloning strategy , two types of cDNA clones with complete cDNA sequences matching the known gastrodianins were obtained from Gastrodia elata f . glauca (Orchidaceae ) and designated gastrodianin-4A
( ga4A) and gastrodianin-4B ( ga4B) , respectively . But only one identical isoform was found to be expressed in all different parts of a single plant . The deduced amino acid sequences of ga4A􊄯-4B accord closely with those of the plant-purified gastrodianins based on the peptide mass fingerprinting analysis . RNA gel blot analyses indicate that gastrodianins were much more abundantly expressed in the fully-opened flowers than the underground corms where an enhanced expression was found in the out layers of secondary corms . From its expression pattern and level in corms , the gastrodianin is assumed to prevent Armillaria hyphae from growing on secondary corms and retard the further penetration of Armillaria hyphae into nutritive corms . Gastrodianins are therefore considered to play a defensive role against the fungus Armillaria . Given the apparently abundant expression in the above-ground parts of the plant, however, gastrodianins seem unlikely to be limited to such a role .

Key words: Gastrodianin

摘要： 基于相似性克隆策略和RT-PCR, 从兰科植物乌天麻( Gastrodia elata f. glauca) 球茎克隆得到两个新的天麻抗真菌蛋白基因, 命名为gastrodianin-4A ( ga4A) 和gastrodianin-4B ( ga4B) , 并首次用Northern 杂交研究了该基因在植物不同部位的转录表达。结果表明, 天麻个体的不同部位只转录表达同一种Gastrodianin基因, 纯化自球茎的Gastrodianin 蛋白质的肽质量指纹谱与推导的Ga4A 和Ga4B 成熟蛋白的氨基酸序列相吻合; Northern 杂交证明天麻的地上器官Gastrodianin 基因转录表达量远远高于地下球茎, 而次生球茎皮层组织的表达量比中柱和整个营繁茎的都高一些。天麻球茎Gastrodianin 的外周表达模式可能是天麻在地下抵御蜜环菌( Armillaria mellea Karst ) 入侵球茎皮层内部的防卫机制之一, 但该基因在天麻地上部分的高丰度表达暗示Gastrodianin 可能蕴藏其它生理功能。

关键词: 天麻抗真菌蛋白, 表达, 乌天麻, 兰科, 蜜环菌FONT