Infanger Li-Chun, Rocheleau Thomas A, Bartholomay Lyric C, Johnson Jody K, Fuchs Jeremy, Higgs Stephen, Chen Cheng-Chen, Christensen Bruce M
Department of Animal Health & Biomedical Sciences, University of Wisconsin-Madison, 1656 Linden Dr., Madison, WI 53706, USA.
Insect Biochem Mol Biol. 2004 Dec;34(12):1329-38. doi: 10.1016/j.ibmb.2004.09.004.
Melanin formation has a significant influence on mosquito vector competence by limiting the development of metazoan parasites. Tyrosine, the rate-limiting substrate of melanin production, can be obtained exogenously or derived from phenylalanine by phenylalanine hydroxylase (PAH). The characteristics of this defense mechanism, such as temporal expression of constituent enzymes involved in the biosynthetic pathway, can vary considerably between mosquito species. We investigated the functional role of PAH in the melanotic encapsulation response in Aedes aegypti and Armigeres subalbatus, two mosquito species with markedly different melanization responses. We used double-stranded RNA (dsRNA) to knock down PAH and observed the phenotypic effects on melanin formation. PAH transcripts were dramatically reduced in both mosquito species after gene knock down. The abundance of PAH proteins was decreased in gene knockdown mosquitoes that were inoculated with Dirofilaria immitis microfilariae (mf) as compared to inoculation controls. A significant reduction of mf melanization also was observed in these knockdown mosquitoes as compared to inoculation controls. Our data suggest that PAH is required for a fully functional melanotic encapsulation response in both mosquito vectors.
黑色素的形成通过限制后生动物寄生虫的发育，对蚊虫的传病媒介能力有重大影响。酪氨酸是黑色素生成的限速底物，可通过外源获取或由苯丙氨酸羟化酶（PAH）将苯丙氨酸转化而来。这种防御机制的特征，如生物合成途径中相关组成酶的时间表达，在不同蚊虫种类间可能有很大差异。我们研究了PAH在埃及伊蚊和骚扰阿蚊这两种黑色素化反应明显不同的蚊虫的黑化包囊反应中的功能作用。我们使用双链RNA（dsRNA）敲低PAH，并观察对黑色素形成的表型影响。基因敲低后，两种蚊虫体内的PAH转录本均显著减少。与接种对照相比，接种犬恶丝虫微丝蚴（mf）的基因敲低蚊虫体内PAH蛋白丰度降低。与接种对照相比，在这些敲低蚊虫中也观察到mf黑化显著减少。我们的数据表明，PAH是两种蚊虫媒介中黑化包囊反应发挥完整功能所必需的。
