低溫逆境下綠豆白化幼苗之RAN polymerases活性與蛋白質合成的探討

Abstract

本篇論文在探討低溫下（10℃和4℃），綠豆白化幼苗的一些生理及生化上的改變，主要包括（A）核醣核酸聚合?（RNA polymerases）的活性變化（B）蛋白質的改變（C）多體（polyribosomes）與單體（monosomes）的變化。 在低溫下，核醣核酸聚合?的活性會降低。以10℃處理一天後，核醣核酸聚合?I和核醣核酸聚合?II的活性變為正常生長溫度28℃時的60％左右。即使再延長處理的天數至3.5天，仍保有55％活性，這顯示出10℃是冷馴化的溫度。若以4℃處理一天時，其活性即下降了75％，且隨著處理的天數而降低。處理3.8天後，酵素活只剩15％，顯示4℃會對綠豆白化幼苗造成嚴重傷害。 低溫會誘導植物合成某些蛋白質，以SDS-polyacryl-amide電泳分析的結果，有三種蛋白質是在低溫下被誘導出來的，分別是19 Kd，23 Kd和74 Kd。以雙向膠體電泳分析的結果，發現經過10℃馴化後的綠豆白化幼苗會合成11種新蛋白質，另外有5種蛋白質的合成完全被低溫抑制。此外，有更多種的蛋白質其合成量或增或減。 合成蛋白質時核醣體會與mRNA結合而形成多體。由實驗結果顯示，低溫處理後多體的量減少，而單體則略增加。對10℃而言，多體的減少和單體的增加有一定的程度。相反地，在4℃下多體會快速地下降，而單體則急劇地增加。

Etiolated mungbean seedlings (Vigna radiata L.), chilling sensitive plant, were used to study some changes during cold acclimation (10℃) and chilling injury (4℃). RNA polymerases activities decrease during both treatments, where 10℃ will cause a decrease of 45% after 3.5-day treatment, compared with a decrease of 85% caused by 3.8-day treatment at 4℃. During cold acclimation, etiolated mungbean seedlings systhesized some new proteins. 19 Kd, 23 Kd and 74 Kd proteins were observed when analyzed by SDS-PAGE. Of these three proteins, 19 Kd protein was thought to have a great deal of importance. Using two-dimentional gel electrophoresis, more changed protein patterns were obtained. There are 11 proteins new synthesized and 5 proteins disappeared during cold acclimation. Two-day-old etiolated mungbean seedling growing at 28℃ contains 70% polysomes and 22% monosomes. The polysomes would decrease to a level of 54% when seedlings were 6-day old. Chilling stresses also caused the decrease of polysomes. At 10℃, polysomes decreased to 41% while monosomes only slightly increased to 28% after 4-day treatment. At 4℃, polysomes declined and monosomes increased following the treatment days. After 4-day treatment, seedlings contained only 30% polysomes but 56% monosomes.