BIOCHEMICAL STUDY OF DNA AND RNA IN OVARY OF TELEOST: A REVIEW

Abstract

RNA/DNA ratios is a fast and reliable method which is used for assessment of fish condition, especially for the short-term study. This technique is based on the assumption that RNA content in cells varies according to the amount of protein synthesis in organisms, but the level of DNA content remains almost the same. Well-developed and healthy fishes demonstrate high RNA/DNA ratios while poorly developed and healthy ones show low RNA/DNA ratios. Non-coding RNAs (ncRNAs) were shown to play various regulatory roles, for example, in reproduction. Thus, an effective reproduction in teleost fishes was correlated with complete realization of the reproduction process, but there are not many publications concerning the role of ncRNAs presence and regulation in mature and immature gonads of fish. RNA content and RNA/DNA ratios proved themselves to be reliable parameters for estimation of growth rate and feeding conditions of fishes in their natural habitats. With the help of meta-analysis of scientific papers published it could be demonstrated that RNA/DNA ratios in larvae of fishes are influenced by starvation and the influence increases with starvation time

            In teleost fishes, the ovaries constitute one of the most dynamic organs, which have nucleic acids acting as major components in their development, functioning, and proliferation. In this review, an attempt has been made to provide an insight into the biochemistry and biological importance of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in the development of ovaries in teleost fishes. DNA content is quite constant and forms an accurate index of cell number, while RNA content depends upon the metabolic activity and protein synthesis. MicroRNAs (miRNAs) are short RNA molecules which act as gene expression regulators at the post-transcriptional level. There is growing recognition that miRNAs act as important regulators of many biological activities including reproductive function. By utilizing expression analysis of miRNAs from fish ovaries, numerous studies have demonstrated the presence of miRNAs in the fish ovary and their regulation during folliculogenesis and hormonal stimulation. Several recent studies using CRISPR/Cas9 gene knockout technique have identified the importance of miR-202 and miR-200 family members located on chromosome 23 for ovarian development, oogenesis, and ovulation in fish species.