Abstract
Members of the testis-specific serine/threonine kinases (Tssk) family play critical roles in spermatogenesis in vertebrates. But in mollusks, research on Tssk family is still lagging. In this study, we systematically identified Tssk family based on the genomic and transcriptomic data from a commercially important scallop Argopecten irradians and detected the spatiotemporal expression in adult gonads. Five members were identified, with the gene length varying from 1,068 to 10,729 bp and the protein length ranging from 294 to 731 aa. All the Tssks possess a serine/threonine protein kinase catalytic (S_TKc) domain. Phylogenetic analysis revealed existence of four homologs of vertebrate Tssk1/2, Tssk3, Tssk4, Tssk5, and absence of Tssk6 in the scallop. The remaining gene (Tssk7) formed an independent clade with Tssks of other mollusks and arthropods, indicating that it may be a new member of Tssk family unique to protostomes. By investigating the expression of Tssks in four developmental stages of testes and ovaries, we found all five Tssks were primarily expressed in mature testis. In situ hybridization experiment revealed the five Tssks were localized in the spermatids and spermatozoa. The testis-predominant expression of Tssk family suggests Tssks may play pivotal roles in spermiogenesis in the scallop. Our study provides basic information on the characteristics and expression profiles of Tssk family of A. irradians. To our knowledge, it represents the first comprehensive analysis of Tssk family in mollusks.
Highlights
Spermatogenesis is a complicated but well-organized process that universally exists in the animal kingdom
Aiming at better understanding and future control of spermatogenesis in simultaneous hermaphrodites, we systematically identified and characterized five testis-specific serine/threonine kinases (Tssk) genes from the genome and transcriptomes of A. irradians and analyzed their temporal and spatial expression patterns in adult gonads
Five members of the Tssk family were identified in the genome of A. irradians, which were named as Tssk1/2, Tssk3, Tssk4, Tssk5, and Tssk7
Summary
Spermatogenesis is a complicated but well-organized process that universally exists in the animal kingdom. It can be divided into three main phases: (1) proliferative phase, in which spermatogonia undergo mitotic division and produce a large number of spermatocytes; (2) meiotic phase, in which haploid spermatids are generated; and (3) spermiogenesis phase, in Expression Profiling of Scallop Tssks which spermatids differentiate into spermatozoa. A large number of serine/threonine kinases and tyrosine kinases have been demonstrated to be expressed at various stages of sperm development (Jenardhanan and Mathur, 2014). Study on these kinases can help to understand the machinery of spermatogenesis
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