FIN219與FHY1基因之間調控關係之研究

Abstract

植物光敏素是一種光接受體，可以感受光照而調節植物生長與發育。在阿拉伯芥中，光敏素A（PHY A）是主要感受遠紅光並調節各種受到遠紅光引發的反應。先前的研究發現了多種PHYA訊息調控因子，例如FIN219 (far-red insensitive 219)以及 FHY1 (far-red elongated hypocoty 1)。已知FIN219基因是專一作用在PHYA調控的遠紅光訊息傳遞的傳訊因子之一，FHY1基因也是參與在遠紅光訊息傳遞的下游。將fin219突變株與fhy1突變株進行雜交測試時，發現F1子代在遠紅光下有長下胚軸外表型，且比個別突變株在heterozygote時的下胚軸長，顯示兩者具有非等位非互補（nonallelic-noncomplementation）的遺傳調控關係，很可能共同參與訊息傳遞的途徑，甚至兩者蛋白質會有結合作用。因此利用酵母菌雙雜交系統測試兩蛋白質之間的結合能力。結果發現FHY1可以與FIN219 C端有結合能力。 當FIN219載體轉殖入fhy1突變株中，遠紅光中生長的轉殖株幼苗，會有比fhy1突變株更短的下胚軸長度，說明fhy1突變株對於遠紅光的感受能力變得比較強；而大量表現FHY1在fin219突變株中，同樣使得轉殖株的下胚軸長度比fin219突變株還要短。此外，北方墨點法的分析結果指出，黑暗中生長的fin219突變株中的FHY1基因表現增加；而黑暗中生長的fhy1突變株中的FIN219基因表現量也會上升。 總結上述結果，認為FIN219與FHY1分處訊息傳遞的兩個平行途徑上，並且具有結合能力而共同調控遠紅光的訊息傳遞。

Phytochromes are plant photoreceptors that regulate plant growth and development in response to the light environment. In Arabidopsis, phytochrome A (phyA) is the primary photoreceptor responsible for perceiving and mediating various responses to far-red light. Previous studies have identified multiple phyA signaling components, such as FIN219 (far-red insensitive 219) and FHY1 (far-red elongated hypocoty 1). FHY1 encodes a product (FHY1) that specifically transduces signals downstream of the far-red (FR) light-responsive phytochrome A (PHYA) photoreceptor. FIN219 is also involved in phytochrome A signaling pathways. Complementation test between fin219 and fhy1 show a nonallelic noncomplementation relationship, indicating possible genetic interactions between these two proteins. Hence, we carry out the yeast 2-hybrid assay to investigate this possibility. The results show that FHY1 protein can interact with FIN219 C-terminus. As well, when the FIN219 overexpression construct was introduced into the fhy1 mutant, the transgenic seedlings show shorter hypocotyls than fhy1 under FR condition, which indicates that the fhy1 mutant gains more sensitivity to the perception of FR light. Moreover, the transgenic seedlings overexpressing the FHY1 in the fin219 mutants also result in a shorter hypocotyl phenotype when compared to that of fin219. In addition, Northern analysis revealed that FHY1 transcript levels arise in fin219 mutants grown in darkness; at the same time, FIN219 transcript levels increase in fhy1 mutant as well. In summary, the results indicate that FIN219 and FHY1 coordinate with each other by direct interaction and response to FR light.