Abstract. Testicular transcriptomes were analyzed to characterize the
differentially expressed genes between mulard and Pekin ducks, which will
help establish gene expression datasets to assist in further determination
of the mechanisms of genetic sterility in mulard ducks. Paraffin sections
were made to compare the developmental differences in testis tissue between
mulard and Pekin ducks. Comparative transcriptome sequencing of testis
tissues was performed, and the expression of candidate genes was verified by
quantitative reverse transcription-polymerase chain reaction (qRT-PCR). In
mulard ducks, spermatogonia and spermatocytes were arranged in a disordered
manner, and no mature sperm were observed in the testis tissue. However,
different stages of development of sperm were observed in seminiferous
tubules in the testis tissue of Pekin ducks. A total of 43.84 Gb of clean
reads were assembled into 193 535 UniGenes. Of these, 2131 transcripts
exhibited differential expression (false discover rate <0.001 and
fold change ≥2), including 997 upregulated and 1134 downregulated
transcripts in mulard ducks as compared to those in Pekin duck testis
tissues. Several upregulated genes were related to reproductive functions,
including ryanodine receptor 2 (RYR2), calmodulin (CALM), argininosuccinate
synthase and delta-1-pyrroline-5-carboxylate synthetase ALDH18A1 (P5CS).
Downregulated transcripts included the testis-specific
serine/threonine-protein kinase 3, aquaporin-7 (AQP7) and glycerol kinase
GlpK (GK). The 10 related transcripts involved in the developmental biological
process were identified by GO (Gene Ontology) annotation. The KEGG (Kyoto
Encyclopedia of Genes and Genomes) pathways indicated that peroxisome
proliferator-activated receptors (PPARs) and calcium signaling pathways were
significantly (P<0.001) associated with normal testis physiology.
The differential expression of select genes implicated in reproductive
processes was verified by qRT-PCR, which was consistent with the expression
trend of transcriptome sequencing (RNA-seq). Differentially expressed candidate genes RYR2, CALM, P5CS,
AQP7 and GK were identified by transcriptional analysis in mulard and Pekin
duck testes. These were important for the normal development of the male
duck reproductive system. These data provide a framework for the further
exploration of the molecular and genetic mechanisms of sterility in mulard
ducks.
Highlights. The mulard duck is an intergeneric sterile hybrid
offspring resulting from mating between Muscovy and Pekin ducks. The
transcriptomes of testis tissue from mulard and Pekin ducks were
systematically characterized, and differentially expressed genes were screened, in
order to gain insights into potential gonad gene expression mechanisms
contributing to genetic sterility in mulard ducks.
The Effect of High-fat Diet and Exercise on KISS-1/GPR54 Expression in Testis of Growing Rats