Department of Entomology and Research Center for Plant Medicine, College of Bioresources and Agriculture, National Taiwan University, Taipei, 10617, Taiwan.
Biodiversity Research Center, Academia Sinica, Taipei, 11529, Taiwan.
BMC Genomics. 2021 Nov 3;22(1):792. doi: 10.1186/s12864-021-08096-x.
The biting midge, Forcipomyia taiwana, is one of the most annoying blood-sucking pests in Taiwan. Current chemical control methods only target the adult, not the immature stages (egg to pupa), of F. taiwana. Discovering new or alternative tactics to enhance or replace existing methods are urgently needed to improve the effectiveness of F. taiwana control. The egg is the least understood life stage in this pest species but may offer a novel point of control as addition of NaCl to the egg environment inhibits development. Thus, the objective of this study was to use RNA profiling to better understand the developmental differences between wild-type melanized (black) and NaCl-induced un-melanized (pink), infertile F. taiwana eggs.
After de novo assembly with Trinity, 87,415 non-redundant transcripts (Ft-nr) with an N50 of 1099 were obtained. Of these, 26,247 (30%) transcripts were predicted to have long open reading frames (ORFs, defined here as ≥300 nt) and 15,270 (17.5%) transcripts have at least one predicted functional domain. A comparison between two biological replicates each of black and pink egg samples, although limited in sample size, revealed 5898 differentially expressed genes (DEGs; 40.9% of the transcripts with long ORFs) with ≥2-fold difference. Of these, 2030 were annotated to a Gene Ontology biological process and along with gene expression patterns can be separated into 5 clusters. KEGG pathway analysis revealed that 1589 transcripts could be assigned to 18 significantly enriched pathways in 2 main categories (metabolism and environmental information processing). As expected, most (88.32%) of these DEGs were down-regulated in the pink eggs. Surprisingly, the majority of genes associated with the pigmentation GO term were up-regulated in the pink egg samples. However, the two key terminal genes of the melanin synthesis pathway, laccase2 and DCE/yellow, were significantly down-regulated, and further verified by qRT-PCR.
We have assembled and annotated the first egg transcriptome for F. taiwana, a biting midge. Our results suggest that down-regulation of the laccase2 and DCE/yellow genes might be the mechanism responsible for the NaCl-induced inhibition of melanization of F. taiwana eggs.
刺吸式蚊虫，比如台湾的冈比亚按蚊，是最令人讨厌的吸血害虫之一。目前的化学控制方法只针对成蚊，而不针对冈比亚按蚊的不成熟阶段（从卵到蛹）。为了提高冈比亚按蚊的防治效果，迫切需要发现新的或替代的策略来增强或替代现有的方法。卵是这种害虫中了解最少的生命阶段，但可能是一个新的控制点，因为向卵环境中添加 NaCl 会抑制发育。因此，本研究的目的是使用 RNA 谱分析来更好地了解野生型黑化（黑色）和 NaCl 诱导的非黑化（粉色）、不育冈比亚按蚊卵之间的发育差异。
用 Trinity 从头组装后，获得了 87415 个非冗余转录本（Ft-nr），N50 为 1099。其中，26247 个（30%）转录本被预测具有长开放阅读框（ORF，这里定义为≥300 nt），15270 个（17.5%）转录本具有至少一个预测的功能域。对每个黑色和粉色卵样本的两个生物学重复进行比较，尽管样本量有限，但发现有 5898 个差异表达基因（DEGs；长 ORF 转录本的 40.9%），差异倍数≥2 倍。其中，2030 个被注释到基因本体论生物过程，并根据基因表达模式可分为 5 个簇。KEGG 通路分析显示，1589 个转录本可被分配到 18 个显著富集的通路，分为 2 个主要类别（代谢和环境信息处理）。正如预期的那样，大多数（88.32%）DEGs 在粉色卵中下调。令人惊讶的是，与色素沉着 GO 术语相关的大多数基因在粉色卵样本中上调。然而，黑色素合成途径的两个关键末端基因，漆酶 2 和 DCE/黄色，显著下调，并通过 qRT-PCR 进一步验证。
我们组装并注释了冈比亚按蚊的第一个卵转录组。我们的结果表明，漆酶 2 和 DCE/黄色基因的下调可能是 NaCl 抑制冈比亚按蚊卵黑化的机制。
