MAPKK Genes In Yesso Scallop(Patinopecten Yessoensis): Gene Structure And Expression Analysis

Mitogen-activated protein kinases (MAPK) signaling pathways transfer extracellular stimuli to the interior of the cell, inducing a series of cellular response and regulating a variety of cellular activities and innate immune responses. Mitogen-activated protein kinase kinases (MKK) can transmit the signals from the upstream MKKK to downstream MAPK. The MKK genes are considered as the hub genes of MAPK signaling pathway. MKK genes in Yesso scallop (Patinopecten yessoensis) were obtained through searching the genome and transcriptome database, and their phylogenetic relationships and expression profiles were analyzed. The results showed that Yesso scallop genome contains a total of five MKK genes (PyMKK), and there is a special Gln repeat region in PyMKK5. The MKK is more conserved between species than between MKK members in a signal species. The expression of all the PyMKKs was detected in scalllop developmental stages (embryos/larvae) and adult tissues. After bacterial infection, the expression level of PyMKK genes experienced significant changes, with significant correlation between some PyMKK members. The main findings are as follows:1 Structure analysis of PyMKKsAfter comprehensive screening in Yesso scallop genome and transcriptome database, five MKK genes (PyMKK1/2, PyMKK4, PyMKK5, PyMKK3/6 and PyMKK7) were identified and characterized. The open reading frames of PyMKK1/2, PyMKK4, PyMKK5, PyMKK3/6 and PyMKK7 was 1206,1143,1401,1107 and 927 bp, encoding 401,380,466,368 and 308 amino acids, respectively. The predicted molecular weight of these PyMKKs was 44.40,43.69,53.21,41.69 and 35.21 kDa, and the predicted isoelectricpoints (pI) was 6.35,6.28,5.44,7.05 and 8.20, respectively. Phylogenetic analysis indicated that PyMKK genes were firstly clustered with other shellfish MKKs, followed by clustering with MKKs in vertebrates. The gene structures of PyMKKs were highly conserved, with characteristic MKK domains, successfully predicted in the corresponding position. There are two, two, one, one and one MAPK docking sites in PyMKK1/2, PyMKK4, PyMKK5, PyMKK3/6 and PyMKK7, respectively; four, one and one 14-3-3 protein family role domains in PyMKK1/2, PyMKK5 and PyMKK3/6, respectively. Other structurally conserved motifs had also been predicted, including GxGxxGxV motifs (parcelling ATP a, y-phosphate groups), HRD KxxN (providing a proton acceptor catalyzed loop, chelating Mg2+), VAIVK, DFG and APE motifs (regulating binding ATP and MKK), PB1 (Phox and Beml) domains belong to MKK5 (mediating dimerization of proteins to realize signal transduction).2 Spatiotemporal expression and analysis of PyMKKs involved in immune defense of the Yesso scallopThree distinct expression patterns were detected among the PyMKKs during different developmental stages. PyMKK genes expression levels was relatively low in umbo larvae and eyespots larvae. In adult scallops, PyMKKs were highly expressed in mantle, gill, muscle and hemolymph, and expression in hepatopancreas, gonad, foot and eye was relatively lower. The expression patterns of PyMKKs after Vibrio anguillarum and Micrococcus luteus infection suggested their involvement in the innate immune response. The expression of PyMKKs after V. anguillarum infection experienced a more dramatic change than after M. luteus infection. For each PyMKK, the expression changing pattern after V. anguillarum and M. luteus infection was similar at each examined time point, except at 24h after infection. These results suggest that PyMKK may play roles in immune response of scallops. This research enriches the understanding of marine shellfish MKK and MAPK signaling pathways, and providing the basis information for further functional study of MKK in shellfish immune reaction.