Vol 49, No 5 (2018)

Callus is an integrated system formed both exogenously (as a result of proliferation of surface cells of different plant tissues) and endogenously (deep in tissues). Initially, callus consists of homogeneous cells gradually transforming into a system of groups of heterogeneous cells with species-specific morphogenetic potencies, which are realized via various pathways of morphogenesis. In this review, issues associated with studying the formation of calli in in vitro cultures of immature anthers and embryos of cultivated cereals are analyzed. Distinguishing the critical stages of callusogenesis is proposed. The features of hemmorhizogenesis in vitro as a type of organogenesis in calli are considered. The concept of the versatility of the processes of plant morphogenesis in vivo, in situ, and in vitro proposed by T.B. Batygina (1987, 1999, 2012, 2014) is confirmed. The prospects of the approach to calli as model systems for studying various problems of plant developmental biology are discussed.

Patterns of mitotic cells’ distribution and activation of the MAP-kinase cascade during the regeneration of Xenopus laevis tadpole tails were studied before and during the refractory period. It is known that the tadpoles of Xenopus laevis are able to fully restore the full structure of the tail after amputation. However, in the refractory period (stage 45–47), the ability to regenerate is significantly reduced, until its complete absence. The mechanisms of this phenomenon are still poorly understood. We conducted a comparative analysis of the average number of mitotic cells on 0–4 days post amputation in normally regenerating tails and in tails amputated during the refractory period. A significant decrease in the number of proliferating cells throughout the surface of the tail in the refractory period compared with their sharp increase in the blastema area in normally regenerating tadpoles was shown. In addition, we detected activation of the MAP-kinase cascade (dpERK1/2) during normal regeneration and demonstrated its full inhibition during the refractory period. At the same time, in the distal part of the tail amputated in the refractory period, activation of the expression of the regenerative marker gene Fgf20 was not detected. Thus, we can conclude that the blocking of the regenerative capacity in tadpoles during the refractory period is accompanied by a sharp suppression of the mitotic activity of the cells and a misregulation of the activation of the Fgf–MAP-kinase cascade in the tail after amputation.

The distribution of the Pax2+ transcription factor in the optic nerve after a mechanical eye injury on the side of damage and in the contralateral nerve has been studied in the trout Oncorhynchus mykiss. It has been found that injury of the optic nerve in this fish species causes Pax2+ reactive astrocytes involved in the initial stages of optic nerve axon regeneration to increase in number, especially in the area of the head and the proximal part of the optic nerve. As the optic nerve in trout is damaged, a significant growth of the heterogeneous population of Pax6+ cells occurs in the brain divisions that have direct retinal inputs, diencephalon, and optic tectum. A part of the Pax6+ cells have an undifferentiated phenotype and are a component of reactive neurogenic niches located in the periventricular zone and parenchymal regions of the brain. Another population of Pax6+ cells has the radial glial phenotype and appears as a result of activation of the constitutive neurogenic domains also within the newly formed reactive neurogenic niches. Thus, due to the optic nerve injury, a pronounced neurogenic response associated with the appearance of reactive neurogenic niches and radial glia arises both in the brain divisions with direct retinal projections and in those lacking the retinal projections as well as in remote regions. The results obtained indicate that the damage to the optic nerve causes an increased reactive neurogenesis in the brain of adult trout.

Preimplantation genetic testing (PGT) is a modern method of detection of chromosomal and genetic abnormalities in a human embryo before its transfer to the uterus. The genetic material is obtained by embryo biopsy. Here, we attempted to evaluate the efficiency of a method of noninvasive biopsy—aspiration of the blastocoel contents (blastocentesis) of human embryos. In this study, a biopsy was carried out human embryos with low morphological characteristics (3–4 CC according to Gardner grading) on day 6–7 of development. DNA obtained from the aspirate, as well as from the blastocyst, was analyzed by QF-PCR (quantitative fluorescent polymerase chain reaction) after whole genome amplification. In total, 24 blastocysts and aspirate samples obtained from them were analyzed; assayable DNA was found in seven (29%) aspirate samples from the blastocyst cavity, and this DNA was identical to blastocyst DNA in five (71%) cases. Thus, it was shown that, using aspiration of the blastocoel fluid of the human embryo, it is possible to obtain DNA suitable for analysis by molecular genetic methods. The features and advantages of the use of multiplex QF-PCR method combined with whole genome amplification for studying DNA obtained during aspiration of the blastocoel fluid are discussed. The prospects of DNA obtainment by the noninvasive biopsy method for preimplantation genetic testing (PGT) in the routine practice of infertility treatment and prevention of chromosomal and genetic abnormalities in newborns are considered.