Molecular Characterization, Tissue Distribution and Localization of Larimichthys crocea Kif3a and Kif3b and Expression Analysis of Their Genes During Spermiogenesis

KIF3A and KIF3B are two N-terminal motor proteins belonging to the kinesin-II superfamily that play essential roles in spermiogenesis.To understand the roles played by KIF3 A/3B during spermatogenesis of large yellow croaker Larimichthys crocea,we studied the testis characteristics at different developmental stages of L.crocea,and determined the spatiotemporal expression patterns of kif3a and kif3b during spermiogenesis.Quantitative real-time PCR(qR T-PCR)showed that the overall trends of kif3 a/3 b m RNA abundance during testis development are similar.From stage Ⅱ to stage V,kif3a/3b m RNA abundances first increased and then fell after reaching a peak at stage IV.Interestingly,the m RNA abundances of both genes at stage V were higher than those at stages Ⅱ and Ⅲ.In addition,it is worth of noting that kif3 b m RNA abundance was higher than that of kif3a at all stages.Fluorescence in situ hybridization results revealed that kif3a/3b m RNA abundance dynamics were consistent with the migration of mitochondria,the deformation of nucleus,and the formation of tail.The m RNA hybridization signals of both genes first appeared either around the nuclear periphery or on the side of the nuclei,then appeared at one side of nuclei,and finally were mainly on the tail during spermiogenesis.Our findings contributed to better understanding the molecular mechanisms of spermiogenesis in fish;and suggested that KIF3A and KIF3B may participate in the intracellular transport of mitochondria,nuclear deformation,and the formation of tail during the spermiogenesis in L.crocea.

Expression Characteristics and Putative Functions of KIF3A/KIF3B During Spermiogenesis of Phascolosoma esculenta

The microtubule(MT)-associated proteins KIF3A and KIF3B are ubiquitously expressed in a wide range of taxa.This study investigated the functions of these proteins in spermiogenesis,which involves various MT-dependent processes,in Phasco-losoma esculenta.We cloned the complete cDNA of Pe-KIF3A/3B.Structural predictions showed that Pe-KIF3A/3B are composed of a highly conserved motor domain,a coiled-coil domain,and a tail domain.Real-time quantitative PCR showed that Pe-kif3a/3b are expressed in all tissues evaluated,with the highest levels in sperm masses.Fluorescence in situ hybridization and immunofluo-rescence were employed to analyze the dynamic expression patterns of KIF3A/3B during spermiogenesis.Pe-KIF3A/3B consistently co-localized with MTs at all stages of spermiogenesis,indicating their potential functions in cargo trafficking.Pe-KIF3A/3B co-localized with mitochondria,suggesting that they may mediate mitochondrial movement.In late-stage spermatids and mature sperm,co-localization was detected in the midpiece,suggesting that Pe-KIF3A/3B could facilitate midpiece formation.The co-localization of Pe-KIF3A and Pe-KIF3B at all stages of spermiogenesis suggests their function as the heterodimeric KIF3AB.Basing on the ob-served temporal and spatial expression patterns of Pe-KIF3A/3B,MTs,and mitochondria in our study,we suggest that heterodimer KIF3AB has a potential role in acrosome biogenesis,sperm head remodeling,enflagellation,and mitochondrial migration during spermiogenesis in P.esculenta.In addition,our study on the morphological characteristics of spermatogenic cells provided fundamental data on the reproductive biology of P.esculenta.