Melanin is involved in cuticle pigmentation and sclerotization of insects,which is critical for maintaining structural integrity and functional completeness of insect cuti-cle.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 in-terference(RNAi),we found that knockdown of BgTH caused molting obstacles in some cockroaches,with the survivors showing pale color and softer integuments,while knock-down 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 pen-etration.These results demonstrate that BgTH and BgDdc function in body pigmentation and affect the waterproofing ability of the cuticle,and the reduction of cuticular perme-ability may be achieved through cuticle melanization.

Tian-Tian Bai;Xiao-Jin Pei;Tong-Xian Liu;Yong-Liang Fan;Shi-Ze Zhang

State Key Laboratory of Crop Stress Biology for Arid Areas and Key Laboratory of Integrated Pest Management on Crops in Northwestern Loess Plateau,Ministry of Agriculture,Northwest A&F University,Yangling,Shaanxi,China;Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology and Institute of Insect Science and Technology,School of Life Sciences,South China Normal University,Guangzhou,510631,China

中国昆虫科学（英文版）

[1]Tian-Tian Bai;Xiao-Jin Pei;Tong-Xian Liu;Yong-Liang Fan;Shi-Ze Zhang-.Melanin synthesis genes BgTH and BgDdc affect body color and cuticle permeability in Blattella germanica)[J].中国昆虫科学（英文版）,2022(06):1552-1568

BgTH,BgDdc,Blattella,germanica,sclerotization,cuti,cockroaches,softer,Desiccation,dsBgTH,dsBgDdc,etration,waterproofing,melanization

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