Date Published: June 13, 2018
Publisher: Public Library of Science
Author(s): Lulu Yan, Chao Zhao, Jun Zhang, Lihua Qiu, Zuozhi Chen, Peng Xu.
Sthenoteuthis oualaniensis (SA) is an important squid species in the South China Sea. Based on SA samples collected in 2016, SA was divided into the “dwarf” form (DF) and “medium” form (MF). To understand the changes in gastrointestinal function in SA during sexual maturation, we undertook transcriptomic analyses of the stomach and intestine tissues of the mature and immature DF and MF of SA using the deep-sequencing platform Illumina HiSeq™. We exploited a high-throughput method to delineate differentially expressed genes (DEGs) in the DF and MF of SA. A total of 135464 unigenes (68627 unigenes of the DG and 66837 unigenes of the MF) were generated. We identified 7965 and 4051 relative DEGs in the intestine and stomach tissues of the mature DF of SA compared with those of the immature DF of SA; and 22138 and 18460 DEGs in the intestine and stomach of the mature MF of SA compared with those of the immature MF of SA. Gastrointestinal function related to the metabolism of lipids, amino acids, glucose, and energy were changed in SA during sexual maturation. This work is the first to identify a set of genes associated with gastrointestinal function during sexual maturation in SA.
Sthenoteuthis oualaniensis (SA; “purpleback flying squid”) is distributed widely along the equator throughout the Indo-Pacific region (40°N to 40°S) [1, 2]. SA is considered to be the most abundant large squid of commercial importance in the region . Within this wide distribution, SA is also known to have a wide ecological amplitude and complex population structure . Two major forms of this species occur in the southern South China Sea based on their morphological characteristics: ‘dwarf’ and ‘medium’. The larger medium form (MF) exhibits a dorsal photophore whereas the dwarf form (DF) does not. [3, 4]. These two forms are also distinct in terms of genetics and morphology. The population structure, sex ratios, sexual maturity, and mortality of the MF and DF have been studied [3, 5].
We employed sequencing technology to compare the transcriptome of common tissues (intestine and stomach) between the mature and immature DFs and MFs of SA. A set of DEGs was found which suggested that gonadal development can cause a dramatic change in the intestines and stomachs of the DF and MF of SA. This work is the first attempt to identify the genes essential to the function of the intestine and stomach during sexual maturation. We employed RNA-Seq to measure the expression of the genes and pathways related to the metabolism of lipids, amino acids, glucose, and energy.
This was the first study of the changes in gastrointestinal function in the DF and MF of SA during maturation using next-generation sequencing technology. A total of 965, 4051, 22138 and 18460 DEGs were altered significantly for PC1, PC2, PC3 and PC4, respectively. Several upregulated and downregulated genes involved in the metabolism of lipids, amino acids, glycogen, and energy were identified. We inferred that sexual maturity may promote lipid metabolism, affect the glycolytic pathway, and absorb energy via oxidative phosphorylation in the intestine and stomach of SA. These results highlight a complex network of nutritional and energy-based metabolic pathways in the intestine and stomach of the DF and MF of SA, and could form the basis of future research.