Molecular identification of two prophenoloxidase-activating proteases from the hemocytes of Plutella xylostella (Lepidoptera: Plutellidae) and their transcript abundance changes in response to microbial challenges.
The phenoloxidase (PO) activation system plays an important role in insect innate immunity, particularly in wound healing and pathogen defense. A key member of this system is prophenoloxidase-activating protease (PAP), which is the direct activator of prophenoloxidase (proPO). Despite their importance in the insect PO activation system, content of studies is limited. In this article, we identify two complementary DNAs (cDNAs), PxPAPa and PxPAPb, encoding possible PAPs, from immunized larval hemocytes of the diamondback moth, Plutella xylostella (L.), by RACE method. PxPAPa is 1,149-bp long and encodes a 382-residue open reading frame (ORF) with a predicted 17-residue signal peptide, a clip domain, and a Tryp_Spc domain. PxPAPb is 1,650-bp long and encodes a 440-residue ORF with a predicted 20-residue signal peptide, two clip domains, and a Tryp_Spc domain. PxPAPa and PxPAPb have a high sequence similarity to Manduca sexta (L.) PAP1 and PAP3, respectively. We also examined the transcript patterns of PxPAPa, PxPAPb, and pxPAP3, another clip-domain serine protease gene, response to different microbial challenges by using real-time quantitative polymerase chain reaction. The results show that the transcript abundance of PxPAPa is significantly increased by Micrococcus luteus and Escherichia coli but not Candida albicans. PxPAPb is induced only by Mi. luteus, whereas pxPAP3 could be induced by all the microbes in the test, but the transcript patterns of Mi. luteus, E. coli, and C. albicans are completely different. This study provides new insights into the molecular events that occur during the immune response, particularly melanization cascade that is involved in encapsulation and nodulation of pathogen or parasite invaders via hemocytes in host insects.
Ministry of Agriculture Key Lab of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, 866 Yuhangtang Rd., Hangzhou 310058, China.
Min
M
Shi
Ministry of Agriculture Key Lab of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, 866 Yuhangtang Rd., Hangzhou 310058, China.
Xiao-Yu
XY
Chen
Ministry of Agriculture Key Lab of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, 866 Yuhangtang Rd., Hangzhou 310058, China.
Ni
N
Zhu
Ministry of Agriculture Key Lab of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, 866 Yuhangtang Rd., Hangzhou 310058, China xxchen@zju.edu.cn.
Xue-Xin
XX
Chen
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D006434:Hemocytes / Q000201:enzymology; D054884:Host-Pathogen Interactions / Q000276:immunology; D007113:Immunity, Innate / Q000235:genetics*; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007814:Larva / Q000201:enzymology; D008969:Molecular Sequence Data; D009036:Moths / Q000502:physiology*; D000073718:Pancreatitis-Associated Proteins; D010802:Phylogeny; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*
D019476:Insect Proteins; D000073718:Pancreatitis-Associated Proteins; C000612141:REG3A protein, human; D012697:Serine Endopeptidases; C022435:prephenoloxidase-activating enzyme
clip-domain serine protease; immunity response; transcriptional character