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

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.

Bivalve mollusc circadian clock genes can run at tidal frequency

“…Tidal expression of Cghiomt may shape the temporal action of melatonin in a tidal manner. Similarly, a tidal rhythmicity of the Cgrhodopsin-likes 1-3, which are homologues of the rhodopsin involved in light signal transduction [32], is observed. One can be argued that this tidal rhythmicity is explained by a tidal periodicity of light availability to the gills inside the palleal cavity, as a result of the valve opening tidal rhythm.…”

“…To investigate the expression of the circadian clock genes in the field, oysters were collected at the same location as for the behavioural study (figure 3 [31], and three rhodopsin-likes genes (Cgrhodopsin-like 1, 2, 3) are known to be associated with light perception [32]. The statistical analysis (figure 3c) using the RAIN algorithm [28] indicated a significant tidal rhythm for five circadian clock genes: Cgclock, Cgbmal1, Cgtim1, Cgror and Cgrev-erb, which peaked during high tide slack.…”

Effects of Light Intensity and Wavelength on the Phototaxis of the Crassostrea gigas (♂) and Crassostrea sikamea (♀) Hybrid Larvae

“…The promotion of red light on eyespot larvae settling was also proposed in the study of C. gigas (Kim et al, 2021). Recently, four rhodopsin-like superfamily genes were identified in the genomic study of C. gigas (Wu et al, 2018), which provided us with another perspective on it.…”

The evo‐devo of molluscs: Insights from a genomic perspective

“…It was further found that gene duplications via retroposition produce intronless opsins (which may be a general feature of G‐protein‐coupled receptors; Brosius, 1999) probably for enhancement of transcription efficiency and generation of new opsin variants by modifications at functional sites may broaden the spectral sensitivity of scallop eyes (Li et al, 2017). It was found that even in the bivalve mollusc without noticeable eyes, vision‐related genes are largely preserved in the genome and such preservation may confer the light‐sensitivity capacity of the animal as validated by an RNA interference experiment (Wu et al, 2018).…”