植物菌質體核醣核酸水解酵素之特性分析

Characterization of a Phytoplasma-related Ribonuclease in Catharanthus roseus (L.) G. Don

絲瓜簇葉病之病原，植物菌質體（phytoplasma）感染日日春，自病株抽取蛋白質，做核醣核酸水解酵素活性分析發現有一酵素蛋白質存在於病株，而不存於健康植株的蛋白質抽出液。此蛋白質的分子量約為6.8 kDa，其等電點介於4-5之間。對此酵素性質作進一步的分析，發現它的活性具有寬廣的pH範圍，由3至8。且其活性對CaCl2及MgCl2敏感，對ZnCl2較不敏感，但不會受EDTA及NaCL之抑制。為了要確定這個水解酵素的出現並非其它環境壓力因子所誘發，因此將健康日日春植物做各種不同的處理，包括加溫、乾旱、酒精、及離層酸等，結果植物體均不能像植物菌質體之感染一樣有6.8 kDa的核醣核酸水解酵素的產生。

A 6.8 kDa ribonuclease protein was found in the protein extract of the diseased periwinkle (Catharanthus roseus (L.) G. Don) infected by the phytoplasma of loofah witches' broom, but not in that of the healthy plants. This protein has an isoelectric point between 4 and 5. Further analyses revealed that it had a broad optimum pH of 3 to 8, and was sensitive to inhibition by CaCl2 (2 mM) and MgCl2 (2 mM) and less seneitive to ZnCl2 (50 µm). but insensitive to EDTA (250 mM) and NaCl (5mM). In order to investigate if this RNase could also be induced by other factors, the healthy periwinkle were given different environmental stress treatments including heat shock. drought , ethanol, and abscisic acid. None of these treatments induced the expression of this phytoplasma-related RNase protein.