Mazari Aslam M A, Dahlberg Olle, Mannervik Bengt, Mannervik Mattias
Department of Neurochemistry, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden.
Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden.
PLoS One. 2014 Oct 16;9(10):e110103. doi: 10.1371/journal.pone.0110103. eCollection 2014.
Organic isothiocyanates (ITCs) are allelochemicals produced by plants in order to combat insects and other herbivores. The compounds are toxic electrophiles that can be inactivated and conjugated with intracellular glutathione in reactions catalyzed by glutathione transferases (GSTs). The Drosophila melanogaster GSTE7 was heterologously expressed in Escherichia coli and purified for functional studies. The enzyme showed high catalytic activity with various isothiocyanates including phenethyl isothiocyanate (PEITC) and allyl isothiocyanate (AITC), which in millimolar dietary concentrations conferred toxicity to adult D. melanogaster leading to death or a shortened life-span of the flies. In situ hybridization revealed a maternal contribution of GSTE7 transcripts to embryos, and strongest zygotic expression in the digestive tract. Transgenesis involving the GSTE7 gene controlled by an actin promoter produced viable flies expressing the GSTE7 transcript ubiquitously. Transgenic females show a significantly increased survival when subjected to the same PEITC treatment as the wild-type flies. By contrast, transgenic male flies show a significantly lower survival rate. Oviposition activity was enhanced in transgenic flies. The effect was significant in transgenic females reared in the absence of ITCs as well as in the presence of 0.15 mM PEITC or 1 mM AITC. Thus the GSTE7 transgene elicits responses to exposure to ITC allelochemicals which differentially affect life-span and fecundity of male and female flies.
有机异硫氰酸酯（ITCs）是植物产生的化感物质，用于对抗昆虫和其他食草动物。这些化合物是有毒的亲电试剂，可在谷胱甘肽转移酶（GSTs）催化的反应中与细胞内谷胱甘肽失活并结合。黑腹果蝇GSTE7在大肠杆菌中异源表达并纯化用于功能研究。该酶对包括苯乙基异硫氰酸酯（PEITC）和烯丙基异硫氰酸酯（AITC）在内的各种异硫氰酸酯表现出高催化活性，这些异硫氰酸酯在毫摩尔饮食浓度下会对成年黑腹果蝇产生毒性，导致果蝇死亡或寿命缩短。原位杂交显示GSTE7转录本对胚胎有母体贡献，在消化道中合子表达最强。涉及由肌动蛋白启动子控制的GSTE7基因的转基因产生了普遍表达GSTE7转录本的存活果蝇。与野生型果蝇接受相同的PEITC处理时，转基因雌性果蝇的存活率显著提高。相比之下，转基因雄性果蝇的存活率显著降低。转基因果蝇的产卵活性增强。在不存在ITCs以及存在0.15 mM PEITC或1 mM AITC的情况下饲养的转基因雌性果蝇中，这种影响很显著。因此，GSTE7转基因引发了对暴露于ITC化感物质的反应，这些反应对雄性和雌性果蝇的寿命和繁殖力有不同影响。
