番茄TDR4在藍光和茉莉酸訊息傳遞中之整合功能性研究

Abstract

本研究分為兩個部分，第一個部份為探討番茄TDR4在藍光與茉莉酸訊息傳遞之間的功能性分析。植物荷爾蒙茉莉酸，在植物防禦反應和生長發育扮演重要角色。過去的研究指出，茉莉酸也能影響果實成熟的過程，然而其相關的調控機制卻尚未明瞭。前人研究發現在藍光處理之下，番茄果皮的TDR4表現量顯著上升, 且TDR4可藉由正向調控果實成熟及類胡蘿蔔素生合成相關基因的表現，增加番茄果皮的茄紅素累積。因此，本研究利用JAR1-like 1 (JRL1)大量表現之番茄轉殖株以及分別由35S啟動子與TDR4自身啟動子所建立之TDR4大量表現轉殖株為材料，將其幼苗與果實交互處理藍光及茉莉酸甲酯，藉由生理性狀的觀察以及基因的表現量分析，來釐清TDR4對於番茄生長發育的影響以及是否參與在茉莉酸的訊息傳遞路徑當中，並探討TDR4和JRL1之間的調控關係。目前的研究結果顯示，TDR4可受茉莉酸所誘導表現，也能正向調控茉莉酸訊息傳遞路徑相關基因的表現。而在藍光處理之下，JRL1也能促進TDR4的表現。此外，TDR4和JRL1對於番茄幼苗下胚軸的抑制具有拮抗現象，而TDR4對於種子產量與節間長度的影響，分別具有負向與正向的調控。綜合以上所述，TDR4可參與在茉莉酸的訊息傳遞路徑中，並會影響番茄的生長發育及果實成熟。本研究的第二部分為探討紅外光對植物光合作用與生長發育的影響。前人研究發現紅外光的處理能增加C4植物PEP carboxylase基因的表現，並且能使玉米與阿拉伯芥葉圓體維持較多的葉綠素含量。因此我們推測，紅外光對於植物具有增加光合作用效率並延緩老化的能力。而本研究實際利用葉菜類幼苗與葉片進行試驗的結果顯示，紅外光確實能延緩蔬菜葉綠素的流失而增加儲藏的時間。此外，紅外光也能增加PEP carboxylase的活性並且增加蔬菜幼苗的生物量。這些結果顯示紅外光的處理對於葉菜類的保鮮與產量上具有實質應用的潛力與價值。

This thesis involves two parts of discussions. The first part attempts to analyze the function of tomato TDR4 in the integration of blue light and jasmonate signaling pathways. Jasmonates (JAs) are plant hormones with essential roles in plant defense and development. Current studies showed that JA might influence fruit ripening processes. However, the regulatory mechanism is still unknown. Our lab found that blue light contributed to the expression of TDR4 in the pericarp of tomato fruit. By positively regulating the expression of fruit ripening and carotenoid biosynthesis related genes, TDR4 enhances the accumulation of lycopene. Thus, this research uses Jasmonate-resistant 1-like1 (JRL1) overexpressing lines as well as TDR4 transgenic lines generated by 35S and the TDR4 native promoter respectively from previous studies, and treats the seedlings and the fruit under blue light along with methyl jasmonate (MeJA). By observing of the phenotype and analyses of mRNA expression levels, we try to link the regulatory relationship between TDR4 and JRL1. Current data show that TDR4 can be induced by MeJA and regulate the expression of JA responsive genes. JRL1 can also up-regulate the expression of TDR4 under blue light. In addition, TDR4 and JRL1 show an antagonistic effect on the inhibition of tomato hypocotyl elongation, and TDR4 poses an influence on the yield of seeds and the internode length positively and negatively, respectively. Taken together, current results indicate that TDR4 participates in JA-mediated growth and fruit ripening in tomato. The other part of this research attempts to study the effect of infrared light (IR) on plant photosynthesis and growth. Our lab found that IR irradiation contributed to the expression of PEP carboxylase gene in C4 plants. Also, IR can maintain higher chlorophyll content in the leaf discs of both maize and Arabidopsis. Therefore, we hypothesize that IR is able to enhance the efficiency of photosynthesis and to delay senescence. By testing vegetable seedlings and leaves, we found that IR can indeed postpone the loss of chlorophyll content, and increase the time of vegetable storage. As well, IR can enhance the activity of PEP carboxylase and the biomass of seedlings, which suggests that IR plays a vital role in enhancing vegetable fresh and yield.