IAPs Gene Expansion in the Scallop Patinopecten yessoensis and Their Expression Profiles After Exposure to the Toxic Dinoflagellate.

Xiaomei Zhu,Xiaoli Hu,Xiaomei Chen,Naina Hu,Shi Wang,Fengmei Zhang,Yinghui Wang,Xiaoting Dai,Zhenmin Bao,Shanshan Lian

doi:10.3389/fphys.2021.633301

Abstract

Inhibitors of apoptosis proteins (IAPs) are conserved regulators involved in cell cycle, cell migration, cell death, immunity and inflammation, should be due to the fact that they can assist with the ability to cope with different kinds of extrinsic or intrinsic stresses. Bivalve molluscs are well adapted to highly complex marine environments. As free-living filter feeders that may take toxic dinoflagellates as food, bivalves can accumulate and put up with significant levels of paralytic shellfish toxins (PSTs). PSTs absorption and accumulation could have a deleterious effect on bivalves, causing negative impact on their feeding and digestion capabilities. In the present study, we analyzed IAP genes (PyIAPs) in Yesso scallop (Patinopecten yessoensis), a major fishery and aquaculture species in China. Forty-seven PyIAPs from five sub-families were identified, and almost half of the PyIAP genes were localized in clusters on two chromosomes. Several sites under positive selection was revealed in the significantly expanded sub-families BIRC4 and BIRC5. After exposure to PST-producing dinoflagellates, Alexandrium catenella, fourteen PyIAPs showed significant responses in hepatopancreas and kidney, and more than eighty-five percent of them were from the expanded sub-families BIRC4 and BIRC5. The regulation pattern of PyIAPs was similar between the two tissues, with more than half exhibited expression suppression within three days after exposure. In contrast to hepatopancreas, more acute changes of PyIAPs expression could be detected in kidney, suggesting the possible involvement of these PyIAPs in tissue-specific PST tolerance. These findings also imply the adaptive expansion of bivalve IAP genes in response to algae derived biotoxins.

Highlights

Apoptosis is a form of programmed cell death, which can be triggered by intrinsic cellular genotoxic stress, or by extrinsic signals such as the ligand binding with cell surface death receptors (Pistritto et al, 2016)
A total of 47 IAP genes were identified from the whole genome of P. yessoensis and they were classified into the five subfamilies, including BIRC1, BIRC4, BIRC5, BIRC6 and BIRC7 (Table 1)
Six BIRC1 members and nine BIRC4 members were identified for PyIAPs, with the rest three classified into BIRC6 and BIRC7 subfamilies, respectively

Summary

Introduction

Apoptosis is a form of programmed cell death, which can be triggered by intrinsic cellular genotoxic stress, or by extrinsic signals such as the ligand binding with cell surface death receptors (Pistritto et al, 2016). In cope with different kinds of stresses, organisms could recruit multiple apoptosis regulators in order to balance between the pro- with anti-apoptotic mechanisms, inhibitors of IAPs in Yesso Scallop P. yessoensis apoptosis proteins (IAPs) for example (Grzybowska-Izydorczyk and Smolewski, 2008). IAPs, known as baculovirus IAP repeat (BIR)-containing proteins (BIRCs), are functionally conserved in metazoans (Fulda and Vucic, 2012). IAP homologous genes could be widely found in insects, birds, fishes, mammals, and viruses (Luque et al, 2002), the IAP gene family vary a lot in gene numbers among species. In human, a total of eight IAP members known as BIRC1-8 were identified through functional screening and homology searching (Salvesen and Duckett, 2002; Vucic, 2008). There are only seven, four and three IAP members were found in sea urchins (Robertson et al, 2006), fruit flies (Jones et al, 2000; Domingues and Ryoo, 2012), sea anemone (Sullivan et al, 2006), respectively, and more than forty IAP members were reported in bivalve mollusc Crassostrea gigas (Zhang et al, 2012), suggesting the adaptive lineage-specific gene gain and loss events

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