利用RNA定序技術探討德國蟑螂對於光照之逆境反應

Abstract

當昆蟲感受到來自生物性或非生物性所引起所謂的「壓力」、「逆境」、「緊迫」（Stress）時，其生理及相關生物化學等內在狀態會相對地予以調整。舉例來說，當擬穀盜被紫外光照射時，其熱休克蛋白（HSPs）、細胞色素P450的基因表現量具有顯著上升。而這些緊迫反應基因（stress response genes）的功能則與去除具危害性的活性氧類（ROS）有關。有趣的是，光對於生物體亦作為調控、影響昆蟲的生理和行為表現的重要環境因子。過去的研究發現兩波長365 nm和490 nm對德國蟑螂（Blattella germanica）行為上的晝夜律動造成不同的影響。因此我們將德國蟑螂長期飼養於（1）持續黑暗；（2）使用廣光譜光源（波長：400－700 nm）以十二小時光照、十二小時黑暗的光週期照射之環境；（3）分別使用365 nm、490 nm以十二小時光照、十二小時黑暗的光週期照射之環境；（4）分別使用波長365 nm、490 nm進行光源的持續照射等處理，並藉由次世代定序技術（RNA-seq），分析得出因處理而具有差異性表現的基因（DEGs）。在本研究中，我們發現當德國蟑螂在波長365 nm的持續照光下，其若蟲階段的時間顯著縮短。另外亦透過基因功能分類（Gene ontology）發現具有表皮、抗氧化酵素功能相關的基因存在。然而我們需要更多的證據，來進一步佐證德光照和德國蟑螂逆境反應的關聯。

While insects suffer from stress, an adaptive response to environmental changes caused by either abiotic or biotic stressors, their endogenous physiology and biochemistry would be modified. For instance, while the red flour beetles (Tribolium castaneum) exposed to ultraviolet (UV) light, the expression levels of stress-response genes, such as heat shock proteins (HSPs) and cytochrome P450s are increased to eliminate the harmful reactive oxygen species (ROS). Intriguingly, light also serves as an environmental cue to affect behavior and regulate endogenous physiology in insects. Previous studies have reported that two wavelengths (365 nm and 490 nm) of light can differently affect the behavioral rhythms of German cockroaches, Blattella germanica. In this study, German cockroaches were reared in the treatments, including (1) constant darkness (DD), (2) broad spectrum (400-700 nm) in LD 12:12 (light-dark cycle), (3) illuminance of the two wavelengths (365 nm and 490 nm) in LD 12:12, and (4) constant light (LL). The technique of RNA-seq was used to identify differentially expressed genes (DEGs). In our study, we observed the German cockroaches exposed to constant UV light have shorter duration of nymph stages than that in other treatments, and the results of gene ontology (GO) reveal some cuticle-related and antioxidant enzyme genes may be involved in the stress responses German cockroaches to light. However, we still need more physiological evidence fort further understanding of relations between light exposure and the stress responses of German cockroaches.