Department of Entomology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran.
Australian Infectious Disease Research Centre, School of Biological Sciences, The University of Queensland, Brisbane, QLD, Australia.
J Insect Physiol. 2019 Oct;118:103939. doi: 10.1016/j.jinsphys.2019.103939. Epub 2019 Sep 4.
Following pathogen attack in a host, widespread changes are induced in the host's gene expression, in particular those involved in the immune system, growth and survival. Epigenetic mechanisms have been suggested to be involved in the regulation of these changes through a number of mechanisms. DNA methylation is one of the important epigenetic processes that is carried out by DNA (cytosine-5) methyltransferase (DNMT) and alters expression of target genes. Here, we identified two putative sequences of DNMT (i.e. DNMT1 and DNMT2) from the transcriptome dataset of Helicoverpa armigera that showed high similarity to the homologous sequences in Bombyx mori. Domain architectures of DNMT1 and DNMT2 exhibit the unique pattern of DNMTs that highlights conserved function of these genes in different insects. To see if these genes play any role in bacterial infection, we challenged the fifth instar larvae of H. armigera by injecting Bacillus thuringiensis and Serratia marcescens cells into the hemolymph. Transcript levels of the DNMTs were analyzed by RT-qPCR. The results showed that the expression levels of DNMT1 and DNMT2 increased in the bacteria-injected larvae. Injection of the heat-killed bacteria also induced the expression of the DNMTs, but lower than that of the live bacteria. To determine whether these genes function during bacterial infection, we injected the inhibitor of DNMTs, 5-azacytidine (5-AZA), into the larvae and 24 h later, the bacterial cells were also injected into the larvae. Bacterial replication and larval mortality were analyzed in the treated and control insects. We found that 5-AZA reduced bacterial replication and also mortality of the bacterial-injected larvae regardless of the pathogenic bacterial species. Interestingly, the expression levels of antimicrobial peptides (AMPs) were also modulated following 5-AZA treatment. In conclusion, we showed that upregulation of the DNMTs in H. armigera following bacterial infections modulates AMPs and thereby affects the insect-bacteria interactions.
在宿主受到病原体攻击后，宿主的基因表达会发生广泛变化，特别是那些与免疫系统、生长和存活相关的基因。表观遗传机制被认为通过多种机制参与这些变化的调节。DNA 甲基化是一种重要的表观遗传过程，由 DNA（胞嘧啶-5）甲基转移酶（DNMT）执行，改变靶基因的表达。在这里，我们从棉铃虫转录组数据集鉴定了两个假定的 DNMT 序列（即 DNMT1 和 DNMT2），它们与家蚕同源序列具有高度相似性。DNMT1 和 DNMT2 的结构域结构表现出独特的 DNMT 模式，突出了这些基因在不同昆虫中的保守功能。为了研究这些基因是否在细菌感染中发挥作用，我们通过向血淋巴中注射苏云金芽孢杆菌和粘质沙雷氏菌细胞来挑战棉铃虫的五龄幼虫。通过 RT-qPCR 分析 DNMT 的转录水平。结果表明，在细菌注射的幼虫中，DNMT1 和 DNMT2 的表达水平增加。热杀死的细菌也诱导了 DNMT 的表达，但低于活细菌的表达。为了确定这些基因在细菌感染过程中是否发挥作用，我们向幼虫注射了 DNMT 抑制剂 5-氮杂胞苷（5-AZA），24 小时后，将细菌细胞也注射到幼虫中。在处理和对照昆虫中分析了细菌复制和幼虫死亡率。我们发现 5-AZA 降低了细菌复制，并且无论致病性细菌种类如何，还降低了细菌注射幼虫的死亡率。有趣的是，5-AZA 处理后抗菌肽（AMPs）的表达水平也发生了调节。总之，我们表明，棉铃虫在细菌感染后 DNMTs 的上调调节 AMPs，从而影响昆虫与细菌的相互作用。
