Starch supplementation modulates amylase enzymatic properties and amylase B mRNA level in the digestive gland of the Pacific oyster Crassostrea gigas

Abstract

In the oyster Crassostrea gigas consumption-related traits, amylase properties and growth were found to be linked through genotypes that differed for polymorphism in the two amylase genes AMYA and AMYB. Modulation of AMYA mRNA level had already been observed in response to food availability, whereas the functional role of AMYB was still unknown. To improve knowledge about the regulation of amylase expression in C. gigas and the respective roles of the two genes, we made an assay of amylase expression at mRNA and enzymatic levels in the digestive gland of oysters that had received dietary supplements of starch. After 18 days, a significant increase of translatable mRNA for AMYB was observed, with a correlated increase in Michaelis-Menten constant Km values and a decrease in total amylase activity. This modulation is the first evidence of observable functioning of AMYB in digestive processes. Amylase B is suggested to display a higher Km than amylase A, offering a means of adapting to high substrate concentrations. The highest starch supplement level (10 mgL(-1)) induced alteration in oyster physiology. The 1 mgL(-1) treatment should be tested as a practical food supplement that could lead to growth benefits for oysters.

Disruption of amylase genes by RNA interference affects reproduction in the Pacific oyster Crassostrea gigas

“…In experiment 1, disruption of reproductive parameters was observed after two dsRNA injections: a slower gametogenesis and a lower reproductive effort that may originate from a disturbance in energy balance linked to the assimilation machinery. This hypothesis is favored over a direct perturbation of the reproductive cascade because no abnormal cytological appearance of germ cells was observed here, in contrast to situations when specific reproductive genes are silenced (Fabioux et al, 2009;Huvet et al, 2012).…”

“…Amplifications of actin and elongation factor 1 cDNA were performed in order to confirm the steady-state level of reference gene expression, providing an internal control for gene expression. Actin and elongation factor 1 primers were those used by Huvet et al (2012) and Fabioux et al (2004), respectively. The calculation of relative AMYA and AMYB mRNA levels was normalized to actin, as no significant differences in C q values were observed for actin between treatments (F=1.65, P=0.201; CV=2.9%) whereas some were noted for elongation factor 1 (F=3.47, P=0.049).…”

“…Food was demonstrated to constitute an external regulatory factor for amylase expression in oyster digestive glands, differently affecting the mRNA expression of both genes. Indeed, AMYA was observed to be regulated at the mRNA level when food varied quantitatively , whereas AMYB was regulated by starch concentration in the food (Huvet et al, 2012); these variations affected amylase enzymatic properties, activity and apparent Michaelis-Menten constant. Associations between amylase expression, growth and consumption-related traits were previously established by studying contrasting genotypes (Prudence et al, 2006;Huvet et al, 2008).…”

Molecular characterization and expression pattern of an α-amylase gene (HcAmy) from the freshwater pearl mussel, Hyriopsis cumingii

“…For instance, the seasonal expression pattern of the α-amylase gene in the bivalve Pecten maximus coincides with the development of phytoplankton blooms (Le Pennec and Le Pennec, 2002). The dietary supplementation of starch upregulated the expression level of the α-amylase gene (AMYB) in the digestive gland of the Pacific oyster C. gigas (Huvet et al, 2012).…”

“…However, knowledge about the molecular characteristics of the α-amylase gene in freshwater mollusks remains limited (Areekijseree et al, 2004). α-Amylase expression is influenced by intrinsic factors, such as hormones and biogenic amines (Giard et al, 1998;Nachman et al, 1999), and extraneous factors, such as food availability (Le Pennec and Le Pennec, 2002;Fernandez-Reiriz et al, 2005;Huvet et al, 2012). However, there is a paucity of information about the effect of the re-feeding regime on the α-amylase expression of bivalves after a period of starvation (Ibarrola et al, 1998;Supannapong et al, 2008).…”