Department of Biochemistry, Kansas State University, 141 Chalmers, Manhattan, KS 66506, USA.
Insect Biochem Mol Biol. 2010 Mar;40(3):267-73. doi: 10.1016/j.ibmb.2010.01.004. Epub 2010 Jan 18.
Newly synthesized insect cuticle is soft and pale but becomes stronger (sclerotized) and often darker (pigmented) over several hours or days. The first step in the sclerotization and pigmentation pathways is the hydroxylation of tyrosine to produce 3,4-dihydroxyphenylalanine (DOPA). Tyrosine hydroxylase (TH) is known to catalyze this reaction during pigmentation, but a role for TH in sclerotization has not been documented. The goal of this study was to determine whether TH is required for cuticle sclerotization in the red flour beetle, Tribolium castaneum. We used quantitative RT-PCR to verify that TH expression occurs at the time of cuticle tanning and immunohistochemistry to confirm that TH is expressed in the epithelial cells underlying sclerotized cuticle. In addition, we found that a reduction in TH function (mediated by RNA interference) resulted in a decrease in cuticle pigmentation and a decrease in the hardness of both pigmented and colorless cuticle. These results demonstrate a requirement for TH in sclerotization as well as brown pigmentation of insect cuticle.
新合成的昆虫外骨骼柔软且苍白，但在数小时或数天后会变得更强硬（硬化），并且通常颜色更深（色素沉着）。在硬化和色素沉着途径的第一步是将酪氨酸羟化为产生 3,4-二羟基苯丙氨酸（DOPA）。酪氨酸羟化酶（TH）已知在色素沉着过程中催化此反应，但 TH 在硬化中的作用尚未有记录。本研究的目的是确定 TH 是否是赤拟谷盗（Tribolium castaneum）外骨骼硬化所必需的。我们使用定量 RT-PCR 来验证 TH 在外骨骼鞣制时表达，并使用免疫组织化学来确认 TH 在硬化外骨骼下方的上皮细胞中表达。此外，我们发现 TH 功能降低（通过 RNA 干扰介导）导致外骨骼色素沉着减少，以及有色和无色外骨骼的硬度降低。这些结果表明 TH 在外骨骼硬化以及昆虫外骨骼的棕色色素沉着中是必需的。
