溫度壓迫對大豆白化幼苗粒線體活性的影響

Abstract

本研究乃以生長兩天的大豆白化幼苗為材料，探討在不同的溫度壓迫下，對其蛋白質合成，呼吸速率，粒線體酵素括性，以及粒線體在試管中合成蛋白質能力的影響。 實驗結果顯示，呼吸速率及酵素活性均隨溫度升高而遞減，尤其以超過41℃(42.5℃及45℃)的處理，活性下降幅度增大，並且當其移至28℃的正常環境3小時後，粒線體酵素活性仍不能恢復，但是若在42.5℃處理之前，先以40℃處理l小時，發現無論呼吸速率或酵素活性所受影響均大為減輕，由此可見該溫度對這些活性的維持是個重要的關鍵點。 大豆幼苗以41℃處理1小時後，再以3H-leucine標識2小時，則可在自動放射顯像圖上，發現其蛋白質合成的類型發生改變。某些在正常溫度下合成的蛋白質消失（或減少），並且出現一些新的蛋白質，而含3H-leucine蛋白質聚集於細胞核部份的比例亦隨之增加，但在粒線體部份，含3H-leucine蛋白質的比例，並未因溫度處理而增加。抽取此部份(mitochondrial fraction)的蛋白質做電泳分析，從自動放射顯像圖中發現其蛋白質類型亦因溫度處理而發生了改變，在其電泳膠質上至少有4條新蛋白質帶出現。 然而植物幼苗若先以不同溫度處理後，將粒線體分離出，做試管中蛋白質的合成。以相同時間內3H-leucineincorporation的放射活性計算，經41℃處理的植物幼苗，其粒線體在試管中傳譯的能力下降了18％左右，然進一步將其在試管中傳譯的產物抽出，做電泳分析，發現與對照組並無任何差異。顯示，前述在invivo標識(labeling)下發現的新蛋白質帶，應是在高溫(41℃)下由細胞質合成後，被運送到粒線體所致。

Two-day-old etiolated soybean seedlings were used to study the effect of temperature on respiration, malate dehydrogenase and NADH dehydrogenase activity in mitochondria, protein synthesis, and in vitro protein synthesis of mitochondria. Following the elevation of temperature, the respiration as well as nalate dehydrogenase and NADH dehydrogenase activity decreased, particularly when temperature was above 41℃. If the seedlings were put back to 28℃ for recovery after 2hr treatment at 41℃, the enzyme activity recovered completely within 3hr. But it was not possible to recover after 42.5℃ treatment. One hour treatment at 40℃ before shifted up to 42.5℃ reduced the effect on reduction in respiration and enzymes activity. It seems that 41℃ is a break point temperature for maintaining normal respiration and enzymes activity. A temperature shift from 28℃ to 41℃ leads a change in the pattern of protein synthesis with at least 8 new heat shock protein bands with molecular weight 88,000, 78,000, 71,000, 65,000, 28,000, 20,000, 16,500, 15,000 dalton in fluorograph as shown by the others. Of which the molecular weight of 88,000, 20,000, 16,500, 15,000 dalton were associated with mitochondria. These proteins were not found in the in vitro mitochondrial translation products from 41℃ treated seedlings. It suggestes that these proteins associated with mitochondria during 41℃ treatment are cytoplasmic origin and are transported to mitochondria.