Immunocytochemical and Ultrastructural Analyses of the Function of the Ubiquitin-Proteasome System During Spermiogenesis with the Use of the Inhibitors of Proteasome Proteolytic Activity in the Alga, Chara vulgaris1

Abstract

Spermiogenesis in Chara vulgaris and in animals share many common features, including exchange of nucleohistones into nucleoprotamines, remodeling and extreme condensation of chromatin, formation of flagellae and of microtubule manchette, and decrease in cytoplasm volume. In C. vulgaris, spermiogenesis is not preceded by meiosis since this alga is a haplobiont. In the present work we showed that in early spermiogenesis characterized by a significant metabolic activity of spermatids, the inhibitors of proteasomes did not visibly change their ultrastructure but significantly prolonged this process. At late stages of spermiogenesis, MG-132 and epoxomicin dramatically changed the structure of nuclei: regular fibrillar and lamellar structure of chromatin was disturbed and clusters of grains corresponding to aggresomes appeared, but the nucleus shape and cytoplasm structure were the same as in the controls. Immunocytochemical studies revealed that these inhibitors blocked disappearance of histones from nuclei while the structures corresponding to aggresomes were clusters of undegraded ubiquitinated histones, since they gave positive immunosignals indicating the presence of ubiquitin and histones.

Transcriptomic analysis of the differentiating ovary of the protogynous ricefield eel Monopterus albus

“…In mammals, Wnt/β-catenin pathway has been shown to be crucial for ovarian differentiation, and β-catenin , is considered as a female-like gene [ 48 ]. In teleosts such as rainbow trout and zebrafish, studies have also implicated Wnt/β-catenin signaling pathway in gonad differentiation [ 49 , 50 ].…”

Gene expression analysis at the onset of sex differentiation in turbot (Scophthalmus maximus)

“…Ctnnb1 is another female-like gene with a critical function in female differentiation in mammals, antagonizing sox9 and blocking testis development, thus promoting ovarian development [ 68 ]. Ctnnb1 is the key downstream component of the canonical wnt signaling pathway and our results are in agreement with a conserved female function of this pathway, which has also been shown in zebrafish [ 69 ] and rainbow trout [ 70 ].…”

“…Among the genes which presented sex dependent temperature effects, ctnnb1 , piwi2 , sf1 and sox6 showed higher expression at low temperatures in males. Among these, ctnnb1 is remarkable because it not only occupies a downstream position in the wnt pathway [ 87 ], which needs to be up-regulated for the development of an ovary in zebrafish [ 68 ], but also because it showed temperature-dependent expression differences in our study at 90 dpf, the onset of SD. Genes found upstream in the wnt signalling pathway are likely regulated by temperature and responsible for this increase in ctnnb1 expression in turbot.…”

Blocking the Bromodomains Function Contributes to Disturbances in Alga Chara vulgaris Spermatids Differentiation

“…Bromodomains bind acetylated lysines, which are present in various proteins i.e., histones playing an important role in chromatin organization during spermiogenesis [27]. The results of previous immunofluorescent and ultrastructural analyses showed that blocking the removal of histones, during the exchange of these proteins into protamines, hindered the proper course of spermiogenesis [3,28]. The studies of spermatogenesis concerning Brdt gene in two fish species, which have different methods of nuclear protein exchange, revealed variations in this gene expression which could indicate a different role of Brdt protein [29].…”