RNA Interference by Ingested Dsrna-Expressing Bacteria to Study Porphyrin Pigmentation in Crassostrea gigas

Abstract

Porphyrins are a widespread group of pigments in nature which are believed to contribute to shell colors in mollusks. Previous studies have provided candidate genes for porphyrin shell coloration, however, the linkage analysis between functional genes and porphyrin pigmentation remains unclear in mollusks. RNA interference is a powerful molecular tool for analyzing the loss of functions of genes in vivo and alter gene expression. In this study, we used unicellular alga Platymonas subcordiformis and Nitzschia closterium f. minutissima as vectors to feed oysters with Escherichia coli strain HT115 engineered to express double-stranded RNAs targeting specific genes involved in porphyrin synthesis. A strain of Crassostrea gigas with orange shell was used to target key haem pathway genes expression using the aforementioned approach. We show here that feeding the oysters with E. coli, containing dsRNA targeting pigmentation genes, can cause changes in the color of the newly deposited shell. For example, the RNAi knockdown of CgALAS and CgPBGD resulted in the loss of uroporphyrin pigmentation from the shell due to the accumulation of the pigment in the oyster’s mantle. The study probed the crucial role of ALAS and PBGD genes potential functions of uroporphyrin production and shell color pigmentation in C. gigas.

De novo genome and transcriptome assembly of Kelletia kelletii, a coastal gastropod and fisheries species exhibiting a northern range expansion

“…The abundance of purine and pyrimidine metabolizing genes has similarly been observed in Macrobrachium olfersi (Jaramillo et al, 2016). Additionally, the high expression of genes related to porphyrin-containing compound metabolism (these compounds contribute to shell pigmentation in other mollusks such as Crassostrea gigas) suggests their involvement in the development of K. kelletii shells (Hu et al, 2021; Figure 7). When comparing the K. kelletii genome annotations and transcriptome HSP gene family counts, we observed a higher number of gene counts for the HSP60/Chaperonin, HSP70, and HSP90 families within the transcriptome, potentially due to alternative splicing that generated multiple viable isoforms.…”

Evolutionary loss of shell pigmentation, pattern, and eye structure in deep‐sea snails in the dysphotic zone

“…2020; Hu et al. 2021a,b). Porphyrin shell pigments are thus not derived from the snail's diet and are instead synthesized by enzymes whose presence and expression are genetically controlled.…”

Toward invasive mussel genetic biocontrol: Approaches, challenges, and perspectives

“…RNAi-based gene knockdown has been tested in a variety of aquatic organisms, such as sea lamprey ( Petromyzon marinus 40 ) and oysters ( Crassostrea gigas 41 , 42 , 43 , 44 , 45 and Crassostrea virginica 46 ). One representative study on RNAi knockdown in bivalves was conducted on C. gigas ; these oysters were injected with HIF-α -targeted long dsRNAs, and after the injection, the knock-down of HIF -α resulted in the production of reactive oxygen species (ROS).…”