Melanin synthesis genes BgTH and BgDdc affect body color and cuticle permeability in Blattella germanica,Insect Science

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Melanin synthesis genes BgTH and BgDdc affect body color and cuticle permeability in Blattella germanica
Insect Science ( IF 2.9 ) Pub Date : 2022-02-22 , DOI: 10.1111/1744-7917.13024
Tian-Tian Bai ₁ , Xiao-Jin Pei _{1,

2} , Tong-Xian Liu ₁ , Yong-Liang Fan ₁ , Shi-Ze Zhang ₁

Affiliation

Melanin is involved in cuticle pigmentation and sclerotization of insects, which is critical for maintaining structural integrity and functional completeness of insect cuticle. The 2 key enzymes of tyrosine hydroxylase (TH) and dopa decarboxylase (DDC) predicted in melanin biosynthesis are usually conserved in insects. However, it is unclear whether their function is related to epidermal permeability. In this study, we identified and cloned the gene sequences of BgTH and BgDdc from Blattella germanica, and revealed that they both showed a high expression at the molting, and BgTH was abundant in the head and integument while BgDdc was expressed highest in the fat body. Using RNA interference (RNAi), we found that knockdown of BgTH caused molting obstacles in some cockroaches, with the survivors showing pale color and softer integuments, while knockdown of BgDdc was viable and generated an abnormal light brown body color. Desiccation assay showed that the dsBgTH-injected adults died earlier than control groups under a dry atmosphere, but dsBgDdc-injected cockroaches did not. In contrast, when dsRNA-treated cockroaches were reared under a high humidity condition, almost no cockroaches died in all treatments. Furthermore, with eosin Y staining assay, we found that BgTH-RNAi resulted in a higher cuticular permeability, and BgDdc-RNAi also caused slight dye penetration. These results demonstrate that BgTH and BgDdc function in body pigmentation and affect the waterproofing ability of the cuticle, and the reduction of cuticular permeability may be achieved through cuticle melanization.

中文翻译：

黑色素合成基因 BgTH 和 BgDdc 影响德国小蠊体色和角质层通透性

黑色素参与昆虫角质层的色素沉着和硬化，这对于维持昆虫角质层的结构完整性和功能完整性至关重要。预测的黑色素生物合成中的酪氨酸羟化酶（TH）和多巴脱羧酶（DDC）这2种关键酶通常在昆虫中是保守的。然而，尚不清楚它们的功能是否与表皮通透性有关。本研究从德国小蠊中鉴定并克隆了BgTH和BgDdc的基因序列，发现它们均在蜕皮时高表达，BgTH在头部和体表中含量丰富，而BgDdc在脂肪体中表达最高。使用 RNA 干扰 (RNAi)，我们发现BgTH的敲低导致一些蟑螂蜕皮障碍，幸存者颜色苍白，体表较软，而BgDdc的敲低是可行的，并产生异常的浅棕色体色。干燥试验表明，在干燥环境下，注射 ds BgTH的成年蟑螂比对照组早死，但注射 ds BgDdc的蟑螂则没有。相比之下，当 dsRNA 处理的蟑螂在高湿度条件下饲养时，几乎没有蟑螂在所有处理中死亡。此外，通过曙红 Y 染色试验，我们发现BgTH -RNAi 导致更高的表皮通透性，并且BgDdc -RNAi 也引起轻微的染料渗透。这些结果表明BgTH和BgDdc在身体色素沉着中起作用并影响角质层的防水能力，并且角质层渗透性的降低可以通过角质层黑化来实现。

更新日期：2022-02-22

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