Cloning of skeletal myosin heavy chain gene family from adult pleopod muscle and whole larvae of shrimps

Transcriptome Analysis Reveals the Tolerance Mechanism of Mantis Shrimp (Oratosquilla oratoria) under a Lipopolysaccharide Challenge

Lipopolysaccharide (LPS), a major cell wall component of Gram-negative bacteria, is considered to lead to some disease development in commercial crustaceans. However, mantis shrimps Oratosquilla oratoria (Crustacea: Stomatopoda) have a strong vitality and ability to resist disease. To study the tolerance mechanism of mantis shrimp, transcriptome analyses were conducted in hepatopancreas of O. oratoria under LPS challenge investigation. Totally, 84 547 044 clean reads were obtained from transcriptomes (43 159 230 in OP (control), 41 387 814 in OL (treatment), respectively). Unigenes, the longest transcript of each gene, with a total length of 68 318 880 bp and the total number of 100 978 were obtained. 8369 (8.28%) of unigenes were successfully annotated in all databases and 54 888 (54.35%) were annotated in at least one database. Finally, 1012 differentially expressed genes (DEGs) including 439 and 573 showed significantly upregulated and downregulated were determined between OL and OP, respectively. Moreover, those DEGs only expressed in OL or OP accounted for 8.99%. The functional classification based on GO and KEGG indicated that the common enrichment categories for the DEGs are "amino sugar metabolic" and "cellular homeostasis" and that the progress of nutrient metabolic and homeostasis in cells is important in facing variable environmental conditions. Protein-protein interaction analysis elucidated proteins, β-actin (ACTB_G1), T-complex protein subunits (TCPs), heat shock proteins (HSPs), hydroxysteroid dehydrogenase-like protein 2 (HSDL2), kinesin family member 5 (KIF5), methylglutaconyl-CoA hydratase (AUH), and myosin heavy chain (MYH) may play key roles in response to an LPS challenge. This study laid a foundation to further investigate the possible adaptation way that O. oratoria survives in a bacterial challenge.

Genome-Wide Identification and Expression Profiles of Myosin Genes in the Pacific White Shrimp, Litopenaeus vannamei

As the main structural protein of muscle fiber, myosin is essential for multiple cellular processes or functions, especially for muscle composition and development. Although the shrimp possess a well-developed muscular system, the knowledge about the myosin family in shrimp is far from understood. In this study, we performed comprehensive analysis on the myosin genes in the genome of the Pacific white shrimp, Litopenaeus vannamei. A total of 29 myosin genes were identified, which were classified into 14 subfamilies. Among them, Myo2 subfamily was significantly expanded in the penaeid shrimp genome. Most of the Myo2 subfamily genes were primarily expressed in abdominal muscle, which suggested that Myo2 subfamily genes might be responsible for the well-developed muscular system of the penaeid shrimp. In situ hybridization detection showed that the slow-type muscle myosin gene was mainly localized in pleopod muscle and superficial ventral muscle of the shrimp. This study provides valuable insights into the evolutionary and functional characterization of myosin genes in shrimps, which provides clues for us to understand the well-developed muscular system of shrimp.

The role of delta-1-pyrroline-5-carboxylate dehydrogenase (P5CDh) in the Pacific white shrimp (Litopenaeus vannamei) during biotic and abiotic stress

Proline (Pro) metabolism is intimately associated with stress adaptation. The catabolism of Pro includes two dehydrogenation reactions catalyzed by proline dehydrogenase (ProDH) and Δ¹-pyrroline-5-carboxylate dehydrogenase (P5CDh). P5CDh is a mitochondrial matrix NAD⁺-dependent dehydrogenase that is critical in preventing P5C-Pro intensive cycling and avoiding ROS production from electron run-off. Little is known about the roles of P5CDh in invertebrates, however. We cloned the P5CDh sequence in the Pacific white shrimp, Litopenaeus vannamei, and found that LvP5CDh is expressed predominantly in pleopod, hepatopancreas and gill. Subcellular localization analysis revealed that LvP5CDh protein was mainly found in the cytoplasm. In addition, overexpressing LvP5CDh in cells reduced ROS formation and inhibited apoptosis induced by LC₅₀ Cd²⁺. Shrimp were exposed to various stress factors including infection with Vibrio alginolyticus, (½ LC₅₀ and LC₅₀) Cd²⁺, acid (pH 5.6) and alkali stress (pH 9.3). Both biotic and abiotic stress resulted in increased LvP5CDh expression and Pro accumulation; V. alginolyticus infection, pH 9.3 and LC₅₀ Cd²⁺ stress apparently stimulated the Glu pathway of Pro synthesis, while pH 5.6 and ½ LC₅₀ Cd²⁺ stress promoted the Orn pathway of Pro synthesis. Silencing of Lvp53 in shrimp attenuated LvP5CDh expression during Cd²⁺ stress, but had no effect on LvP5CDh mRNA levels if no Cd²⁺ stress was imposed. Our study contributes to the functional characterization of LvP5CDh in biotic and abiotic stress and reveals it to protect against ROS generation, damage to the cell, including the mitochondria, and apoptosis. Thus, LvP5CDh plays a critical role in immune defense and antioxidant responses.

Changes in free amino acid concentrations and associated gene expression profiles in the abdominal muscle of kuruma shrimp Marsupenaeus japonicus acclimated at different salinities

Shrimps inhabiting the coastal water can survive in a wide range of salinity. However, the molecular mechanisms involved in their acclimation to different environmental salinities have remained largely unknown. In the present study, we acclimated kuruma shrimp Marsupenaeus japonicus at 1.7 %, 3.4 % and 4.0 % salinities. After acclimating for 6, 12, 24 and 72 h, we determined free amino acid concentrations in their abdominal muscle, and performed RNA-seq analysis on this muscle. The concentrations of free amino acids were clearly altered depending on salinity after acclimating for 24 h. Glutamine and alanine concentrations were markedly increased following the increase of salinity. In association with such changes, many genes related to amino acid metabolism changed their expression levels. In particular, the increase of the expression level of the gene encoding glutamate-ammonia ligase which functions in the glutamine metabolism appeared to be relevant to the increased glutamine concentration at high salinity. Furthermore, the alanine concentration increased at high salinity was likely to be associated with the decrease in the expression levels of the alanine-glyoxylate transaminase gene. Thus, there is a possibility that changes in the concentration of free amino acids for osmoregulation in kuruma shrimp are regulated by changes in the expression levels of genes related to amino acid metabolism.

Shared gene structures and clusters of mutually exclusive spliced exons within the metazoan muscle myosin heavy chain genes

Multicellular animals possess two to three different types of muscle tissues. Striated muscles have considerable ultrastructural similarity and contain a core set of proteins including the muscle myosin heavy chain (Mhc) protein. The ATPase activity of this myosin motor protein largely dictates muscle performance at the molecular level. Two different solutions to adjusting myosin properties to different muscle subtypes have been identified so far: Vertebrates and nematodes contain many independent differentially expressed Mhc genes while arthropods have single Mhc genes with clusters of mutually exclusive spliced exons (MXEs). The availability of hundreds of metazoan genomes now allowed us to study whether the ancient bilateria already contained MXEs, how MXE complexity subsequently evolved, and whether additional scenarios to control contractile properties in different muscles could be proposed, By reconstructing the Mhc genes from 116 metazoans we showed that all intron positions within the motor domain coding regions are conserved in all bilateria analysed. The last common ancestor of the bilateria already contained a cluster of MXEs coding for part of the loop-2 actin-binding sequence. Subsequently the protostomes and later the arthropods gained many further clusters while MXEs got completely lost independently in several branches (vertebrates and nematodes) and species (for example the annelid Helobdella robusta and the salmon louse Lepeophtheirus salmonis). Several bilateria have been found to encode multiple Mhc genes that might all or in part contain clusters of MXEs. Notable examples are a cluster of six tandemly arrayed Mhc genes, of which two contain MXEs, in the owl limpet Lottia gigantea and four Mhc genes with three encoding MXEs in the predatory mite Metaseiulus occidentalis. Our analysis showed that similar solutions to provide different myosin isoforms (multiple genes or clusters of MXEs or both) have independently been developed several times within bilaterian evolution.