可做抗病毒目標之寄主因子篩選

Abstract

病毒入侵寄主之初期，和寄主所產生的交互作用常決定了病毒是否可在寄主中複製及侵染。為了瞭解病毒感染初期和寄主產生的交互作用，針對病毒感染初期所誘發的寄主轉錄體變化進行探討，以阿拉伯芥的cDNA microarray分析TMV複製早期寄主轉錄體的變化，發現到一寄主基因PAP85於一般發育階段無明顯表現，但在TMV感染初期其會被穩定的正向調控，而藉由PAP85的負向調控可對病毒的累積產生抑制效果，進一步研究顯示TMV可能會利用PAP85去影響寄主內質網的結構以促進病毒複製複合體的生合成。此外一轉錄因子WRKY6會於病毒感染後4小時被正向調控，先前之研究已知WRKY6參與了植物的抗性反應，而進一步於WRKY6大量表現或抑制表現的原生質體及植物中分析TMV的累積情況，結果顯示WRKY6雖然在病毒複製初期無顯著影響，但WRKY6於植物中同時扮演了促進和抑制TMV感染的角色。而為了瞭解組蛋白修飾過程是否亦參與在病毒感染初期和寄主產生之交互作用，我們針對組蛋白乙醯化酶(HATs)及組蛋白去乙醯化酶(HDACs)進行突變株的篩選及分析，結果發現到一CBP family的HAT基因(HAC2)於TMV在原生質體中的累積扮演重要角色。綜合這些結果顯示，在病毒感染初期和寄主產生交互作用時，寄主的基因表現、轉錄因子和組蛋白修飾過程皆可能會受到調控，而藉由控制這些被病毒調控的寄主因子也許可在病毒防治上提供可行的策略及方法。

The early stage of interaction between viruses and hosts is a detrimental step for successful virus replication and further infection. In order to understand the early stage of interaction during virus infection, the host transcriptome change in response to virus early infection was studied. Arabidopsis cDNA microarray was conducted to monitor host transcriptome change during the early stage of infection of Tobacco mosaic virus (TMV). A host gene, PAP85, with low expression level in most development stages but continuatively up-regulated in early stage of TMV infection was identified. Virus accumulation could be inhibited by down-regulation of PAP85. My data also indicated that TMV may adapt PAP85 to alter endoplasmic reticulum (ER) structure in facilitating the formation of virus replication complexes. A transcription factor (TF), WRKY6, which was up-regulated at 4 hour post virus infection was selected for further study. The WRKY6 TF was known to involve in plant resistance to pathogens in previous studies. TMV inoculation assay was conducted in WRKY6-overexpressed and -knockout protoplasts and plants. Although WRKY6 may not have the effect on the initial establishment of virus replication, WRKY6 plays both supportive and inhibitory roles in TMV accumulation. I also tried to understand whether histone modification are involved in early stage of virus infection. I performed mutant screening of histone acetyltransferase (HATs) and histone deacetylases (HDACs), and identified one of the HATs, HAC2, belonging to CBP family was required for TMV accumulation in Arabidopsis protoplasts. Combined these findings indicate that regulation of host gene expression, TF and histone modification are all involved in the early stage of virus-host interaction. Controlling these factors which are altered by virus infection in early stage may be a practicable and valid strategy in virus management.