阿拉伯芥 hit1-1 和 hit2 為經由前項式遺傳學方法所找到的熱敏感突變株。 HIT1 在胺基酸序列比對後發現為酵母菌 Vps53p 的同源性蛋白質。酵母菌的 Vps53p是和Vps51p、Vps52p、Vps54p共同組合 GARP (Golgi-associated retrograde protein) 複合體的一個次單元，參與調節內膜體至高爾基氏體之間的反向囊泡運輸。 hit1-1 的對熱不耐受性可能是由於飽和脂肪酸的囊泡運輸過程發生問題，使得細胞膜在高溫逆境下無法調整脂質成份提高熱穩定性。 HIT2 基因所表現的蛋白質為一核運輸受器，參與調節抵抗高溫誘發氧化傷害的機制中。而 hit2 無法耐受持續性高溫逆境以及熱休克逆境，部份原因為光照所誘導活性氧化物質攻擊造成。由於葉綠體類囊膜的熱穩定性與光合作用效率對環境溫度的改變非常敏感，可用來作為探討植物在高溫逆境下所遭受生理傷害的研究指標，並提供線索以作為解析突變基因參與之保護機制。而葉綠素螢光分析為近年來廣泛用於環境逆境生理研究的重要實驗技術，能以簡單且不破壞植物的方式研究植物的葉綠體及光合作用。本篇論文主要透過熱誘導葉綠素螢光 (heat-induced chlorophyll fluorescence) 來度量 WT 、 hit1-1 與 hit2 類囊膜 (thylakoid membrane) 之熱穩定性，並以光化學參數 (F'v/ F'm) 來檢驗 hit1-1 、 hit2 與WT 在常溫與熱逆境下光合作用的效率。結果則吻合先前 HIT1 和 HIT2 所參與不同耐熱機制的推論。hit1-1 and hit2 are two Arabidopsis heat-intolerant mutants which were found by a forward genetics approach. HIT1 is homologous to yeast Vps53p, which is a subunit of Golgi-associated retrograde protein (GARP) complex. GARP complex is required for tethering of endosome-derived transport vesicles to the late Golgi. The heat intolerance phenotype of hit1-1 is thought to be resulted from the inability to remodel plasma membrane under heat stress condition. As for HIT2, it encodes a nuclear transport receptor and the heat-intolerance phenotype was caused in part by heat-induced light-dependent oxidative stress. The chloroplast and photosynthesis are also affected under heat stress. They can be a way to research plant physiological damage under heat stress. Chlorophyll fluorescence is a phenomenon of chlorophyll molecules that is very sensitive to changes in environmental temperatures and useful for study plant physiological conditions under heat stress. In this study, heat-induced chlorophyll fluorescence and quantum yield of photosystem II were measured from WT, hit1-1 and hit2 plants under normal and high temperature conditions. Results were in agreement with that HIT1 and HIT2 participate in different heat-protecting mechanism in plants.
