State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, 400715, People's Republic of China.
College of Biotechnology, Southwest University, Chongqing, 400715, People's Republic of China.
Parasit Vectors. 2019 Sep 24;12(1):460. doi: 10.1186/s13071-019-3714-2.
Female Aedes aegypti mosquitoes are vectors of arboviruses that cause diverse diseases of public health significance. Blood protein digestion by midgut proteases provides anautogenous mosquitoes with the nutrients essential for oocyte maturation and egg production. Midgut-specific miR-1174 affects the functions of the midgut through its target gene serine hydroxymethyltransferase (SHMT). However, less is known about SHMT-regulated processes in blood digestion by mosquitoes.
RNAi of SHMT was realized by injection of the double-stranded RNA at 16 h post-eclosion. The expression of SHMT at mRNA level and protein level was assayed by real-time PCR and Western blotting, respectively. Statistical analyses were performed with GraphPad7 using Student's t-test.
Here, we confirmed that digestion of blood was inhibited in SHMT RNAi-silenced female A. aegypti mosquitoes. Evidence is also presented that all SHMT-depleted female mosquitoes lost their flight ability and died within 48 h of a blood meal. Furthermore, most examined digestive enzymes responded differently in their transcriptional expression to RNAi depletion of SHMT, with some downregulated, some upregulated and some remaining stable. Phylogenetic analysis showed that transcriptional expression responses to SHMT silence were largely unrelated to the sequence similarity between these enzymes.
Overall, this research shows that SHMT was expressed at a low level in the midgut of Aedes aegypti mosquitoes, but blood-meal digestion was inhibited when SHMT was silenced. Transcriptional expressions of different digestive enzymes were affected in response to SHMT depletion, suggesting that SHMT is required for the blood-meal digestion in the midgut and targeting SHMT could provide an effective strategy for vector mosquito population control.
雌性埃及伊蚊是携带虫媒病毒的媒介，这些病毒会导致多种具有公共卫生意义的疾病。中肠蛋白酶对血液蛋白的消化为卵母细胞成熟和产卵提供了内源性蚊子所需的营养物质。中肠特异性 miR-1174 通过其靶基因丝氨酸羟甲基转移酶 (SHMT) 影响中肠的功能。然而，关于蚊子血液消化中 SHMT 调节过程的了解较少。
在出茧后 16 小时通过注射双链 RNA 实现 SHMT 的 RNAi。通过实时 PCR 和 Western blot 分别测定 SHMT 在 mRNA 水平和蛋白水平的表达。使用 GraphPad7 通过 Student's t-test 进行统计分析。
在这里，我们证实了 SHMT RNAi 沉默的雌性埃及伊蚊中血液消化受到抑制。还有证据表明，所有 SHMT 耗尽的雌性蚊子在吸血后 48 小时内丧失了飞行能力并死亡。此外，大多数检查的消化酶在其转录表达对 SHMT RNAi 耗尽的反应中表现出不同，有些下调，有些上调，有些保持稳定。系统发育分析表明，转录表达对 SHMT 沉默的反应与这些酶之间的序列相似性关系不大。
总的来说，这项研究表明 SHMT 在埃及伊蚊中肠中表达水平较低，但当 SHMT 沉默时，血液消化受到抑制。不同消化酶的转录表达受到 SHMT 耗竭的影响，这表明 SHMT 是中肠血液消化所必需的，靶向 SHMT 可能为蚊虫种群控制提供有效的策略。
