A Rhodopsin-Like Gene May Be Associated With the Light-Sensitivity of Adult Pacific Oyster Crassostrea gigas.

Changlu Wu,Lei Wei,Qiuyun Jiang,Xiaotong Wang,Wen Guo,Zhongqiang Cai,Wenchao Yu,Jiao Wang,Cheng He,Jun Chen

doi:10.3389/fphys.2018.00221

Changlu Wu, Lei Wei + Show 8 more

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https://doi.org/10.3389/fphys.2018.00221

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Abstract

Light-sensitivity is important for mollusc survival, as it plays a vital role in reproduction and predator avoidance. Light-sensitivity has been demonstrated in the adult Pacific oyster Crassostrea gigas, but the genes associated with light-sensitivity remain unclear. In the present study, we designed experiments to identify the genes associated with light-sensitivity in adult oysters. First, we assessed the Pacific oyster genome and identified 368 genes annotated with the terms associated with light-sensitivity. Second, the function of the four rhodopsin-like superfamily member genes was tested by using RNAi. The results showed that the highest level of mRNA expression of the vision-related genes was in the mantle; however, this finding is not true for all oyster genes. Interestingly, we also found four rhodopsin-like superfamily member genes expressed at an very high level in the mantle tissue. In the RNAi experiment, when one of rhodopsin-like superfamily member genes (CGI_1001253) was inhibited, the light-sensitivity capacity of the injected oysters was significantly reduced, suggesting that CGI_10012534 may be associated with light-sensitivity in the adult Pacific oyster.

Highlights

Until recently, four classes of molluscs (Gastropoda, Bivalvia, Polyplacophora, and Cephalopoda) have been demonstrated as possessing light sensitive organs (Serb and Eernisse, 2008)
We demonstrated that adult oysters are light-sensitive (Wu et al, 2015), but the genes associated with light-sensitivity remain uncertain
It has been previously assumed that the adult oyster did not need the ability to sense light, because oysters have a sessile lifestyle after larva settlement and metamorphosis (Zhang et al, 2012)

Summary

Introduction

Four classes of molluscs (Gastropoda, Bivalvia, Polyplacophora, and Cephalopoda) have been demonstrated as possessing light sensitive organs (Serb and Eernisse, 2008). Light-sensitive organs play an important role in reproduction and predator avoidance for the above molluscs (Wu et al, 2015). Eyes from molluscan lineages could be used to study convergence and parallel patterns of eye evolution (Nilsson and Kelber, 2007; Serb and Eernisse, 2008). Light-sensitivity in oyster larvae has previously been confirmed (Magalhães et al, 2014; Xu et al, 2015; Wheeler et al, 2017). After the occurrence of eyespot, the oyster larvae use their left shell to fix on the surface of rocks and other solid surfaces, and they no longer move after attachment. Light-sensitivity does not significantly impact the movement of adult oysters, it may play

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