The Sry‐related high mobility group box (Sox) genes family is a group of transcription factors playing crucial roles during reproduction and development. At least 50% amino acid sequences of Sox protein family are similarity to the sex‐determining region on the Y chromosome (Sry). The sox family exists throughout the invertebrates and vertebrates and plays an important role in sex determination and differentiation, gonadal development, neurogenesis, formation of multiple tissues and organs, early embryonic development, chondrocyte differentiation, cardio‐vascular system, and other features in fish. The full characters of sox genes at the genome‐wide level have been reported in many fish species, due to the rapid development of high‐throughput DNA sequencing technique and massive accumulation of genomic data. Here, the research progress of fish sox gene family is reviewed to provide the latest information for the research in this field.

The order Acipenseriformes, which includes sturgeons and paddlefishes, represents “living fossils” with complex genomes that are good models for understanding whole-genome duplication (WGD) and ploidy evolution in fishes. Here, we sequenced and assembled the first high-quality chromosome-level genome for the complex octoploid Acipenser sinensis (Chinese sturgeon), a critically endangered species that also represents a poorly understood ploidy group in Acipenseriformes. Our results show that A. sinensis is a complex autooctoploid species containing four kinds of octovalents (8n), a hexavalent (6n), two tetravalents (4n), and a divalent (2n). An analysis taking into account delayed rediploidization reveals that the octoploid genome composition of Chinese sturgeon results from two rounds of homologous WGDs, and further provides insights into the timing of its ploidy evolution. This study provides the first octoploid genome resource of Acipenseriformes for understanding ploidy compositions and evolutionary trajectories of polyploidy fishes.

In this study, the effects of different feeding frequencies on the growth and the expression of genes in the GH/IGF axis were assessed in juvenile Chinese sturgeon. The newly hatched Chinese sturgeons were bred for 38 days at three different feeding frequencies groups (feeding frequency of two times a day, TWD; three times a day, THD; and four times a day, FOD), and the expression levels of the GH/IGF axis responses to feeding frequency were determined by quantitative real-time PCR. In addition, the full-length of the Coding Sequences of IGF I and IGF II genes (489-bp and 660-bp, respectively), were cloned and analyzed from Chinese sturgeon the first time. Multiple sequence alignments of IGFs revealed that Chinese sturgeon are high sequence identity to IGFs from other species. The phylogenetic relationships based on the IGF I and IGF II amino acid sequences were consistent with the traditional classification. After 38 days of growth, the three different feeding frequencies groups of Chinese sturgeon had no significant difference of body length, body weight, specific growth rate, the survival rate, the rate of weight gain and the condition factor. However, the relative expression of Chinese sturgeon GH in the pituitary decreased with increasing feeding frequency. The relative expression of Chinese sturgeon GHR in liver and skeletal muscle was deceased with increasing feeding frequency, while the relative expression of GHR in stomach and intestines at THD group was significantly higher than that of at TWD group and FOD group (p < 0.05). The relative expression of Chinese sturgeon IGF I in liver increased significantly with increasing feeding frequency (p < 0.05). The relative expression of IGF I in stomach and skeletal muscle was similar at the three groups. The relative expression of IGF I in intestines was significantly higher at FOD group than at TWD group and THD group (p < 0.05). The relative expression of Chinese sturgeon IGF II in liver at TWD group was significantly higher than that at THD group and FOD group (p < 0.05). However, the relative expression of IGF II in stomach, intestines and skeletal muscle at THD group was higher than that at TWD group and FOD group. Based on these previous studies that liver IGF I is regarded as a biomarker of growth performance, this result suggested that the juvenile Chinese sturgeon is better for growth when feeding four times daily compared to twice and thrice daily.

Elongases of very-long-chain fatty acids (Elovls) are critical rate-limiting enzymes that are involved in LC-PUFA biosynthesis through catalyzing the two-carbon elongation of a pre-existing fatty acyl chain. Thus far, several Elovls have been extensively studied in teleost. However, the functional and physiological roles of Elovls in chondrichthyans have rarely been reported. In this study, we identified and characterized elovl2 from the endangered Chinese sturgeon (Acipenser sinensis) by whole genome scanning. The results show that the coding sequence of elovl2 was 894 bp in length, for a putative protein of 297 amnio acids. Comparative genomic analyses indicated that Chinese sturgeon elovl2 was evolutionarily conserved. Functional characterization in yeast demonstrated that the Chinese sturgeon Elovl2 could efficiently elongate C₂₀ (ARA and EPA) and C₂₂ (22:4n-6 and 22:5n-3) substrates, confirming its critical roles in LC-PUFA biosynthesis. Spatial and temporal expression analyses showed high elovl2 mRNA levels were detected in the liver and brain and showed an increase trend both in embryonic and post-hatching stages. Interestingly, diets with vegetable oils as lipid sources could significantly induce the high expression of elovl2 in Chinese sturgeon, implying that the endogenous LC-PUFA biosynthesis pathway was stimulated by lack of LC-PUFA in their diets. Our findings will enhance our understanding about the evolutionary and functional roles of elovl2 and provide novel insights into the LC-PUFA biosynthesis mechanism in vertebrates.

Chinese sturgeon (Acipenser sinensis) has been listed as a critically endangered species on the IUCN Red List and is an endemic fish of China. Five sets of duplex polymerase chain reactions (PCR) assays were developed with 10 tetranucleotide microsatellites for Chinese sturgeon. The size of CS57, ZHX43, ZHX69, AS105, ZHX51, AS074, ZHX2, AS078, AS026 and AS073 products in 184 Chinese sturgeon individuals ranged from 257–305, 191–241, 251–285, 172–244, 236–260, 169–209, 194–234, 92–176, 165–257 and 120–164, respectively. The observed allele number of the 10 microsatellites ranged from 7 to 16, and the total number of alleles was 106. The number of alleles per individual in CS57, ZHX43, AS105, AS074, AS078 and AS026 was 1–4. The number of alleles per individual in ZHX69, ZHX51, ZHX2 and AS073 was 2–4. The mean number of alleles per locus per individual ranged from 2.01–3.76. The expected heterozygosity (H_E), observed heterozygosity (H_O), polymorphic information content (PIC) and Shannon-Weiner diversity index (H′) ranged from 0.582 to 0.899, from 0.676 to 1, from 0.518 to 0.886 and from 1.034 to 2.34, respectively. Despite many advantages, the use of microsatellites as genetic analysis tools can be limited by the cost of the associated experiment. To solve this problem, this set of five duplex PCRs will provide tools that are more helpful, less expensive and less time consuming than others used for genetic analyses in Chinese sturgeon.

This study investigated the effects of vitamin E supplementation on growth performance, antioxidant capacity, and hepatic lipid metabolism in one-year-old juvenile Chinese sturgeon (Acipenser sinensis). A total of 270 fish (initial weight 1.37 ± 0.04 kg) were allocated into 9 fiberglass tanks and fed isonitrogenous and isolipidic diets with graded concentrations of vitamin E (DL-α-tocopherol acetate) including, 0, 1000, and 2000 mg/kg, respectively, for 2 months. Results showed that 1000 mg/kg vitamin E significantly improved growth performance and decreased hepatosomatic index. Dietary vitamin E supplementation significantly reduced the hepatic crude protein and crude lipid levels, withnot significantly affecting moisture and crude ash. Dietary vitamin E led to significant increases in plasma high-density lipoprotein cholesterol and vitamin E levels, while decreasing plasma low-density lipoprotein cholesterol. Additionally, it raised liver vitamin E content and reduced hepatic triglycerides, total cholesterol, crude protein, and crude lipid levels. Vitamin E also significantly downregulated mRNA levels of lipogenesis-related genes (ACC1, acetyl-CoA carboxylase 1; FASN, fatty acid synthase; and PPARγ, peroxisome proliferator activated receptor γ) and inhibited the enzyme activities of ACC1 and FASN, while upregulating lipolysis-related genes (HSL, hormone-sensitive lipase; CPT1, carnitine palmitoyltransferase 1α, and PPARα, peroxisome proliferator activated receptor α) and enhancing the activities of HSL and CPT1α. Furthermore, vitamin E supplementation significantly improved plasma reduced glutathione and superoxide dismutase activities, lowered plasma reactive oxygen species, malondialdehyde levels, and hepatic malondialdehyde contents, and upregulated mRNA levels of hepatic Nrf2 (nuclear factor-erythroid 2 related factor 2), Keap1 (Kelch-like epichlorohydrin associating protein 1), and CuZnSOD (copper/zinc superoxide dismutase). In conclusion, dietary 1000 mg/kg vitamin E supplementation could improve growth performance, enhance antioxidant capacity, and reduce liver fat deposition, indicating its potential as a beneficial dietary additive for promoting health and lipid regulation in juvenile Chinese sturgeon.