In many arthropod species including insects, the cuticle tanning pathway for both pigmentation and sclerotization begins with tyrosine and is responsible for production of both melanin- and quinoid-type pigments, some of which are major pigments for body coloration. In this study we identified and cloned cDNAs of the yellow mealworm, Tenebrio molitor, encoding seven key enzymes involved in this pathway including tyrosine hydroxylase (TmTH), DOPA decarboxylase (TmDDC), laccase 2 (TmLac2), Yellow-y (TmY-y), arylalkylamine N-acetyltransferase (TmAANAT1), aspartate 1-decarboxylase (TmADC) and N-β-alanyldopamine synthase (Tmebony). Expression profiles of these genes during development were analyzed by real-time PCR, revealing development-specific patterns of expression. Loss of function mediated by RNAi of either 1) TmTH or TmLac2, 2) TmDDC or TmY-y, and 3) TmAANAT1, TmADC or Tmebony resulted in pale/white, light yellow/brown and dark/black adult body coloration, respectively. In addition, there are three distinct layer/regional pigmentation differences in rigid types of adult cuticle, a brownish outer exocuticle (EX), a dark pigmented middle mesocuticle (ME) and a transparent inner endocuticle (EN). Decreases in pigmentation of the EX and/or ME layers were observed after RNAi of TmDDC or TmY-y. In TmADC- or Tmebony-deficient adults, a darker pigmented EX layer was observed. In TmAANAT1-deficient adults, trabeculae formed between the dorsal and ventral elytral cuticles as well as the transparent EN layer became highly pigmented. These results demonstrate that knocking down the level of gene expression of specific enzymes of this tyrosine metabolic pathway leads to abnormal pigmentation in individual layers and substructure of the rigid adult exoskeleton of T. molitor.

中文翻译：

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基因在黄粉虫黄粉虫的成年表皮色素沉着中起作用。

在包括昆虫在内的许多节肢动物物种中，用于色素沉着和硬化的表皮鞣制途径始于酪氨酸，并负责产生黑色素和醌型色素，其中一些是人体着色的主要色素。在这项研究中，我们鉴定并克隆了黄粉虫Tenebrio molitor的cDNA，编码这条途径中涉及的七个关键酶，包括酪氨酸羟化酶（TmTH），DOPA脱羧酶（TmDDC），漆酶2（TmLac2），黄色y（TmY-y）。 ），芳基烷基胺N-乙酰基转移酶（TmAANAT1），天冬氨酸1-脱羧酶（TmADC）和N-β-丙氨酰多巴胺合酶（Tmebony）。通过实时PCR分析了这些基因在发育过程中的表达谱，揭示了发育特异的表达模式。RNAi介导的功能丧失：1）TmTH或TmLac2，2）TmDDC或TmY-y，和3）TmAANAT1，TmADC或Tmebony分别导致成年人的身体呈浅色/白色，浅黄色/棕色和深色/黑色。另外，在成年角质层的硬质类型，外表皮褐色（EX），中层角质层深色（ME）和内层角质透明（EN）中，存在三种明显的层/区域色素沉着差异。TmDDC或TmY-y的RNAi后，观察到EX和/或ME层的色素沉着减少。在TmADC或Tmebony缺乏的成年人中，观察到较深色的EX层。在缺乏TmAANAT1的成年人中，在背侧和腹侧表皮角质层之间形成的小梁以及透明的EN层变得高度着色。