阿拉伯芥中FIN219與隱花色素參與乙烯反應的分子機制的研究

Abstract

乙烯是一種氣態的植物荷爾蒙，調控植物的生長發育與防禦反應。在黑暗環境下處理乙烯，阿拉伯芥幼苗會呈現三重反應的外表型，包含過度卷曲的頂端鉤、較粗較短的下胚軸、延長受到抑制的根。先前的研究中得知FIN219與隱花色素可能參與乙烯訊息傳遞的調控；但其調控的分子機制，則尚未瞭解。檢測隱花色素與fin219突變株對ACC的敏感性，發現fin219、cry1、35S::GUS-CCT1轉殖株與cry1 cry2雙突變株對外加乙烯生合成前驅物ACC呈現較敏感的反應，cry2則無顯著的差異。暗示FIN219與CRY1可能為乙烯訊息傳遞的負調控者。此結果與參與乙烯生合成或訊息傳遞的相關基因在fin219或cry1突變株中表現量上升是一致的。進一步檢測cry1 fin219雙突變株與cry1 cry2 fin219三突變株對ACC的敏感性，則與野生型沒有差異。有趣的是，在FIN219大量表現於cry1的轉殖株中，卻呈現較敏感的外表型，然而在FIN219大量表現於cry1 cry2雙突變的轉殖株中，卻回復成野生型的敏感性；推測FIN219可負向調控乙烯的訊息傳遞，並且需要CRY2的輔助。除此之外，添加甲基化茉莉酸(MeJA)會部份回復fin219突變株中對ACC的過敏感外表型，而添加JA-Ile相似物coronatine (COR)則可以完全回復成類似野生型的外表型。綜合上述的結果，我們推論FIN219與CRY1共同負向調控乙烯的訊息傳遞；此外，FIN219可透過活化茉莉酸訊息傳遞達到抑制乙烯在幼苗時期對頂端鉤與下胚軸發育的調控。

Ethylene, a gaseous phytohormone, participates in the regulation of plant development and defense responses. Dark-grown Arabidopsis seedlings under ethylene treatment exhibit triple response phenotype, including exaggerated apical hooks, shortened and thickened hypocotyls, and shortened roots. Previous studies indicated that FIN219 and cryptochromes may regulate ethylene responses. However, the molecular mechanisms underlying their involvement in ethylene signaling remain unknown. Here, we found that fin219, cry1, 35S::GUS-CCT1, and cry1 cry2 were hypersensitive to ACC, but the cry2 mutant showed a sensitivity similar to that in wild-type Columbia (Col). This result indicates that FIN219 and CRY1 negatively regulate ethylene responses, which is consistent with the fact that several ethylene biosynthetic genes. In addition, signaling related genes are also increased in both fin219 and cry1 mutants. Moreover, the cry1 fin219 double mutant and the cry1 cry2 fin219 triple mutant exhibited ACC sensitivities similar to Col. Intriguingly, FIN219 overexpression in cry1 mutant resulted in a hypersensitive response to ACC, but in cry1 cry2 double mutant did not, which implies that FIN219 may negatively regulate ethylene responses with a requirement of the functional CRY2. In addition, MeJA application can partially rescue the hypersensitive responses of the fin219 mutant to ACC, and the coronatine, a JA-Ile analog can fully rescue the defect in ACC responses of the fin219 mutant. Taken together, these data indicate that FIN219 negatively regulates ethylene responses through JA signaling.