Nielsen K K, Mikkelsen J D, Kragh K M, Bojsen K
Maribo Seed Biotechnology, DANISCO A/S, Copenhagen K, Denmark.
Mol Plant Microbe Interact. 1993 Jul-Aug;6(4):495-506. doi: 10.1094/mpmi-6-495.
An acidic chitinase (SE) was found to accumulate in leaves of sugar beet (Beta vulgaris) during infection with Cercospora beticola. Two isoforms, SE1 and SE2, with MW of 29 kDa and pI of approximately 3.0 were purified to homogeneity. SE2 is an endochitinase that also exhibits exochitinase activity, i.e., it is capable of hydrolyzing chito-oligosaccharides, including chitobiose, into N-acetyl-glucosamine. Partial amino acid sequence data for SE2 were used to obtain a cDNA clone by polymerase chain reaction. The clone was used to isolate a cDNA clone encoding SE2. The deduced amino acid sequence for SE2 is 58-67% identical to the class III chitinases from cucumber, Arabidopsis, and tobacco. A transient induction of SE2 mRNA during the early stages of infection with C. beticola is much stronger in tolerant plants than in susceptible plants. Transgenic tobacco (Nicotiana benthamiana) plants constitutively accumulate SE2 protein in the intercellular space of their leaves. In a preliminary infection experiment, the transgenic plants did not show increase in resistance against C. nicotianae.
发现在甜菜（Beta vulgaris）感染甜菜尾孢菌期间，一种酸性几丁质酶（SE）在叶片中积累。纯化得到了两种同功酶SE1和SE2，分子量为29 kDa，pI约为3.0，且均达到了同质纯。SE2是一种内切几丁质酶，也表现出外切几丁质酶活性，即它能够将包括壳二糖在内的壳寡糖水解为N-乙酰葡糖胺。利用SE2的部分氨基酸序列数据通过聚合酶链反应获得了一个cDNA克隆。该克隆用于分离编码SE2的cDNA克隆。推导得到的SE2氨基酸序列与黄瓜、拟南芥和烟草的III类几丁质酶有58 - 67%的同源性。在甜菜尾孢菌感染早期，SE2 mRNA的瞬时诱导在耐病植株中比在感病植株中要强得多。转基因烟草（Nicotiana benthamiana）植株在其叶片的细胞间隙中持续积累SE2蛋白。在初步的感染实验中，转基因植株对烟草尾孢菌的抗性并未增强。
