土壤中根圈微生物分泌的各種代謝物對植物有不同程度的影響，其中一群代謝物以氣態方式存在於環境中。這些由微生物分泌出的氣態代謝物稱為微生物揮發性有機物(microbial volatile organic compounds, mVOCs)，前人研究多以微生物釋出的混合mVOCs作為探討的對象，甚少人深入研究其中的成分影響。本研究主要分析植物抑制生長細菌Enterobacter aerogenes釋出的有機揮發化合物，發現主要抑制菸草生長的化合物為混合mVOCs中含量第二高的C2，且透過次世代定序(NGS)分析發現當菸草暴露在E.aerogenes揮發物或C2揮發性化合物時，自噬作用、囊泡運輸、氮運輸關鍵基因表現量上調，推測當菸草處於E.aerogenes揮發物或C2揮發性化合物時會啟動自噬作用、囊泡運輸、氮運輸等反應，以抵禦mVOCs的侵害。為更進一步確認囊泡運輸在防禦上的作用，運用病毒誘導基因靜默技術(virus-induced gene silence, VIGS)將參與自噬作用中的囊泡運輸基因Exo70靜默。發現NbExo70靜默植株對E.aerogenes揮發物及C2揮發性化合物較為敏感，且相較於野生型，NbExo70靜默植株經過E.aerogenes揮發物及C2揮發性化合物處理後過氧化物的累積情況較不顯著。由上述結果可推測Exo70在逆境下會誘導過氧化物的累積，當過氧化物累積時會啟動過敏反應引起的細胞程序性死亡(HR-PCD)反應，然而為了避免累積過多時造成HR-PCD反應失控，因此Exo70會在過氧化物累積過多時協助自噬體，將產生過氧化物訊號的蛋白質運送至液泡中降解。而當NbExo70靜默時不會有過氧化物累積現象，亦不存在HR-PCD反應失控的問題。另外細胞壁沉積程度在未處理mVOCs時，NbExo70靜默植株較野生型薄，但經mVOCs處理後NbExo70靜默植株卻比野生型厚，推測Exo70雖然會參與細胞壁沉積，但在逆境下為加強防禦植物會啟動其他機制促使細胞壁沉積。

Microbes affect plant growth through several mechanisms. One of the mechanisms affected by microbial volatile organic compounds (mVOCs) are gaseous molecules released by microbes. There are lots of reports that focus on the influence by mixing mVOCs. Just a few researches have analyzed the compositions of mVOCs. Here I analyzed two volatile organic compounds, which are released by Enterobacter aerogenes, a plant growth-inhibiting bacteria. I found the major inhibiting compound, C2, the second large compound in E. aerogenes mVOCs. Using next generation sequencing technique, I found that the key genes of autophagy, exocyst and asparagines synthesis were up regulated when tobacco was exposed to mVOCs of E. aerogenes or C2 compound. To further confirm how vesicle trafficking results in tobacco defense mechanism, virus-induced gene silence (VIGS) was performed to silence Exo70, an important gene participates in autophagy process. NbExo70 silenced tobacco was sensitive to mVOCs of E. aerogenes and C2 compound. H2O2 was not accumulated in leaves when NbExo70 silenced tobacco exposed to mVOCs of E. aerogenes and C2 compound. According to the results I can conclude that Exo70 induces the accumulation of H2O2. The accumulation of H2O2 would induce hypersensitive response programmed cell death(HR-PCD). When the level of H2O2 was abnormal accumulation, it would disturbe the HR-PCD of plant. Thus, Exo70 would help the autophagosomal degradation of H2O2 signaling related protein. NbExo70 silenced tobacco has less deposition in callose, but when it is exposed to mVOCs of E. aerogenes and C2 compound the deposition in callose will be higher than wild-type. It seems that Exo70 is involved in callose deposition, but when under the stress tobacco will turn on another mechanism.

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