Effect of Heat Starvation Stress on Physiological Immunity and Metabolism of <i>Mizuhopecten yessoensis</i>

Mizuhopecten yessoensis is an economical maricultural bivalve mollusk in China and Japan. Due to the high mortality rate, academics have paid more attention to the effects of the environment recently. However, little is known about the physiological, immune, and metabolic effects of M. yessoensis under starvation stress at high temperatures. Herein, transcriptomic libraries of hemolymph and striated adductor muscle from feeding and starved M. yessoensis were constructed. The results showed that the immune indexes decreased in the concentration of M. yessoensis blood cells and liver lysozyme activity at 15 d, M. yessoensis fertility and liver ACP at 30 d of starvation stress, and T-AOC and BCA at 45 d of starvation stress. A total of 853.85 M clean reads were obtained from 20 libraries, with an average total mapping ratio of 83.38% to the reference genome. Based on an examination of the genes that differ in expression between the fasted and feeding groups, 27 up- and 41 down-regulated DEGs were identified in hemolymph, while the numbers in striated adductor muscle were 426 up- and 255 down-regulated. Determined by GO annotation and KEGG pathway mapping, annotations and categories of the DEGs presented diverse biological functions and processes. KEGG analysis showed that most downregulated DEGs in striated muscle were enriched in the pathways involved in metabolism. Genes encoding the enzymes, including eno, pgk, gapA, tpiA, fbp, pgi, and pgm in the gluconeogenesis pathway, were down-regulated, which was indicative of the negative effect of long-term starvation on gluconeogenesis. The down-regulation of PGD and tktA genes in the pentose phosphate pathway suggested that the carbohydrate decomposition and utilization were decreased in starved scallops. Together, the findings demonstrated the influences of food deprivation on carbohydrate metabolism and other processes in M. yessoensis. These results provide foundational information for further understanding of metabolism, especially carbohydrate metabolism of scallops under starvation, which may potentially benefit healthy aquaculture

KEGG annotation of putative proteins.

<p>A, Cellular Processes; B, Enviromental Information Processing; C, Genetic Information Processing; D, Metabolism; E, Organismal Systems.</p

GO (Gene Ontology) categorization (Biological process, Cellular component and Molecular function) of unigenes in sea cucumber.

<p>Each annotated sequence is assigned at least one GO term. The x-axis represents GO subcategories. The left y-axis indicates the percentage of genes. The right y-axis indicates the number of DEGs.</p

Key DEGs associated with cellular processes.

<p>Key DEGs associated with cellular processes.</p

Significantly enriched GO terms in DEGs.

<p>Significantly enriched GO terms in DEGs.</p

Enriched pathways in DEGs.

<p>Enriched pathways in DEGs.</p

Transcriptome analysis of the sea cucumber (<i>Apostichopus japonicus</i>) with variation in individual growth

<div><p>The sea cucumber (<i>Apostichopus japonicus</i>) is an economically important aquaculture species in China. However, the serious individual growth variation often caused financial losses to farmers and the genetic mechanisms are poorly understood. In the present study, the extensively analysis at the transcriptome level for individual growth variation in sea cucumber was carried out. A total of 118946 unigenes were assembled from 255861 transcripts, with N50 of 1700. Of all unigenes, about 23% were identified with at least one significant match to known databases. In all four pair of comparison, 1840 genes were found to be expressed differently. Global hypometabolism was found to be occurred in the slow growing population, based on which the hypothesis was raised that growth retardation in individual growth variation of sea cucumber is one type of dormancy which is used to be against to adverse circumstances. Besides, the pathways such as ECM-receptor interaction and focal adhesion were enriched in the maintenance of cell and tissue structure and communication. Further, 76645 SSRs, 765242 SNPs and 146886 ins-dels were detected in the current study providing an extensive set of data for future studies of genetic mapping and selective breeding. In summary, these results will provides deep insight into the molecular basis of individual growth variation in marine invertebrates, and be valuable for understanding the physiological differences of growth process.</p></div

Distribution of SSR motifs.

<p>Different colors represent different repeat types.</p

KOG classification of putative proteins.

<p>KOG classification of putative proteins.</p