The habitat of Drosophila melanogaster is the environment of fruit decay/fermentation which emits high concentrations of chemicals. Our recent studies revealed that D. melanogaster has been evolutionarily adapted to its habitat through tolerance to chemicals and induction of antimicrobial peptides (AMPs) plays an important role for chemical tolerance. To determine the correlation between AMPs and the chemical tolerance pathway, we hypothesized that expression of AMPs is induced by tissue damages or ROS caused by chemical exposure and AMPs activate antioxidant enzymes, thereby inducing chemical tolerance in D. melanogaster. Therefore, in this study, we investigated the induction levels of genes associated with necrosis (EGR and BSK), apoptosis (Dronc, Dcp1, and Drice), antioxidant physiology (SOD1, SOD2, CAT, Trxr1, GstD2, and GstD5), and SAM metabolism (Gnmt and Foxo) in D. melanogaster exposed to three chemicals, 2-phenylethanol, ethanol, and acetic acid. As a result, above genes were induced in chemical-exposed fly, and this supports our hypothesis of chemical tolerance pathway in D. melanogaster.

Drosophila melanogaster is mainly found in fermented and rotten fruits and is tolerant to chemicals emitted during the fermentation process. Its distinctive habitat suggests an evolutionary adaptation to environmental chemicals. In order to understand the physiological adaptation of D. melanogaster to the chemicals, we treated LC20 concentration of three chemicals (acetic acid, ethanol and 2-phenylethanol) and differential expression of the female whole body transcripts were compared with control fly (no chemical treatment). Compared to control fly, 94, 137 and 59 genes were up-regulated, while 85, 184 and 166 genes were down-regulated in acetic acid, 2-phenylethanol and ethanol treated flies, respectively. According to the KEGG enrichment analysis, genes categorized in metabolic pathway, Toll/IMD signaling pathway, lysosome and autophagy were ranked in the top groups of most changed gene sets after three chemical treatment. In addition, we selected 7 genes showing different expression levels in transcriptome analysis, and investigated their expression changes in the flies exposed to various concentration of three chemicals using quantitative PCR.

The fruit fly, Drosophila melanogaster, is a good model organism in various areas of biological science. Since D. melanogaster has been thought to be adapted to the chemical stress environment caused by the overripen, decay and fermented fruits, identification of the genes involved in chemical tolerance and investigation of their expression patterns are essential for better understanding of the physiological evolution in D. melanogaster. For investigation of the gene expression level, quantitative real-time PCR (qRT-PCR) can be applied to quantify gene expression level and selection of reliable reference gene(s) for normalization is an accurate step. In the present study, therefore, we validated the expression stabilities of ten candidate reference genes using three softwares (geNorm, NormFinder and BestKeeper) in D. melanogaster exposed to different concentrations of acetic acid, ethanol and 2-phenylethanol. Although three programs resulted in slightly different gene stability ranks, but overall tbp encoding TATA box binding protein was most stable gene in acetic acid and ethanol exposed fly, while nd encoding NADH dehydrogenase was the most suitable reference gene in the case of 2-phenylethanol treatment. In the comparison of three chemical treatment condition, nd was also suggested to be most optimal reference gene. In addition, optimal number of reference gene for accurate normalization was calculated by geNorm pairwise analysis, and selection of multiple reference genes was suggested to be better for target gene normalization method than use of a single reference gene.

토양수분은 지면환경에서 일어나는 수문 순환을 이해하기 위한 중요한 기상인자일 뿐만 아니라 가뭄, 홍수, 산불 등과 같은 자연재해와 밀접하게 연관되어 있다. 그러나 위성기반 토양수분 자료는 공간해상도가 매우 떨어져서 국지규모 분석에 직접적 으로 적용하기에는 한계가 있다. 이 연구에서는 마이크로파 위성센서로부터 산출된 토양수분 자료가 가지는 공간해상도의 제약을 완화하기 위하여, 다양한 지면 변수와 공간통계법을 활용한 다운스케일링 기법을 도입하였다. 가장 정교한 다운스케일링 기법으로 평가되는 회귀크리깅을 이 연구를 통하여 토양수분 자료에 처음으로 적용하였다. 우리나라의 2013년과 2014년의 4월부터 10월까지 의 일자별 AMSR2(Advanced Microwave Scanning Radiometer 2) 공간해상도 10km와 25km의 토양수분 자료를 각각 2km와 4km로 다운스케일링한 결과, 고해상도로 다운스케일링된 자료와 저해상도 원자료와의 일관성이 우수하게 유지되어, 다운스케일링 전후의 공간패턴과 자료특성이 잘 보존되는 것을 확인할 수 있었다. 이 연구에서 제시한 다운스케일링 기법은 토양수분뿐만 아니라 여러 기상요소에 적용될 수 있으며, 위성영상이나 모형자료의 공간해상도 한계를 극복하기 위한 방편이 될 수 있을 것으로 기대된다.