Identification of Sex-Specific Markers Reveals Male Heterogametic Sex Determination in Pseudobagrus ussuriensis

Abstract

Comprehending sex determination mechanism is a first step for developing sex control breeding biotechnologies in fish. Pseudobagrus ussuriensis, one of bagrid catfishes in Bagridae, had been observed to have about threefold size dimorphism between males and females, but its sex determination mechanism had been unknown. In this study, we firstly used the amplified fragment length polymorphism (AFLP)-based screening approach to isolate a male-specific DNA fragment and thereby identified a 10,569 bp of male-specific sequence and a 10,365 bp of female-related sequence by genome walking in the bagrid catfish, in which a substantial genetic differentiation with 96.35 % nucleotide identity was revealed between them. Subsequently, a high differentiating region of 650 bp with only 70.26 % nucleotide identity was found from the corresponding two sequences, and three primer pairs of male-specific marker, male and female-shared marker with different length products in male and female genomes, and female-related marker were designed. Significantly, when these markers were used to identify genetic sex of the bagrid catfish, only male individuals was detected to amplify the male-specific marker fragment, and female-related marker was discovered to produce dosage association in females and in males. Our current data provide significant genetic evidence that P. ussuriensis has heterogametic XY sex chromosomes in males and homogametic XX sex chromosomes in females. Therefore, sex determination mechanism of P. ussuriensis is male heterogametic XX/XY system.

Extra Microchromosomes Play Male Determination Role in Polyploid Gibel Carp

“…The reasons might derive from two characteristics. One might be that only a lower genetic differentiation exists between this male-specific sequence and the corresponding female-homologous sequence, as reported in other fish species (Dan et al, 2013;Pan et al, 2015). Another might be related to the LTR retrotransposon sequence and various repetitive sequences (Figure 5): perhaps it is the complicated retrotransposon and repetitive sequences and their accumulation (Estep et al 2013) in the polyploid gibel carp, especially after two rounds of polyploidy (Li et al, 2014b), that leads to the difficulty in discrimination.…”

“…To detect genomic differences between the female and male offspring of DA♀ 3 A♂, bulked segregant analysis (BSA) through AFLP was carried out as described previously (Pan et al 2015). Nine female and nine male individuals were used to make three respective pools, and a total of 256 EcoRI/MseI primer combinations were screened in the six pools (male pools one, two, and three; and female pools four, five, and six).…”

“…To screen the genetic difference between females and males, we employed an AFLP-based screening approach (Pan et al 2015) using 256 EcoRI/MseI primer combinations (Table S1). All the primer combinations produced almost identical AFLP patterns between pools of males (pools one, two, and three) and pools of females (pools four, five, and six), except the E15/M5 primer combination, which was able to be used to produce a male-specific AFLP band ( Figure 1A).…”

“…The amplified fragment length polymorphism (AFLP) procedure was performed as described previously (Vos et al 1995;Wang et al 2009) with five main procedures: (1) digestion of DNA with endonucleases EcoRI and MseI and subsequent ligation of adaptors, (2) amplification of the resulting fragments using preselective primers with one selective nucleotide, (3) amplification of the diluted products using selective primers with three selective nucleotides, (4) electrophoretic separation of the fragments in 6% denatured polyacrylamide gels, and (5) visualization of the fragments via silver staining. The sequences of the adapters and the primers are summarized in Supplemental Material, Table S1.To detect genomic differences between the female and male offspring of DA♀ 3 A♂, bulked segregant analysis (BSA) through AFLP was carried out as described previously (Pan et al 2015). Nine female and nine male individuals were used to make three respective pools, and a total of 256 EcoRI/MseI primer combinations were screened in the six pools (male pools one, two, and three; and female pools four, five, and six).…”

Induction of meiotic gynogenesis in bagrid catfish (Pseudobagrus ussuriensis) with homologous sperm and its confirmation for female homogamety

“…Pseudobagrus ussuriensis, which is widely distributed in East Asia, is the largest of the bagrid catfish species (Pan, Li, Zhou, Qiang & Gui, ). With its chewy flesh and appealing taste, this fish is well liked by Chinese consumers (Wang et al., ).…”