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...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.展开更多
基金supported by the National Natural Science Foundation of China(grant no.31772533)。
文摘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.
