DNA Repair Repertoire of the Enigmatic Hydra

Abstract

Since its discovery by Abraham Trembley in 1744, hydra has been a popular research organism. Features like spectacular regeneration capacity, peculiar tissue dynamics, continuous pattern formation, unique evolutionary position, and an apparent lack of organismal senescence make hydra an intriguing animal to study. While a large body of work has taken place, particularly in the domain of evolutionary developmental biology of hydra, in recent years, the focus has shifted to molecular mechanisms underlying various phenomena. DNA repair is a fundamental cellular process that helps to maintain integrity of the genome through multiple repair pathways found across taxa, from archaea to higher animals. DNA repair capacity and senescence are known to be closely associated, with mutations in several repair pathways leading to premature ageing phenotypes. Analysis of DNA repair in an animal like hydra could offer clues into several aspects including hydra’s purported lack of organismal ageing, evolution of DNA repair systems in metazoa, and alternative functions of repair proteins. We review here the different DNA repair mechanisms known so far in hydra. Hydra genes from various DNA repair pathways show very high similarity with their vertebrate orthologues, indicating conservation at the level of sequence, structure, and function. Notably, most hydra repair genes are more similar to deuterostome counterparts than to common model invertebrates, hinting at ancient evolutionary origins of repair pathways and further highlighting the relevance of organisms like hydra as model systems. It appears that hydra has the full repertoire of DNA repair pathways, which are employed in stress as well as normal physiological conditions and may have a link with its observed lack of senescence. The close correspondence of hydra repair genes with higher vertebrates further demonstrates the need for deeper studies of various repair components, their interconnections, and functions in this early metazoan.

New Insights on the Diurnal Mechanism of Calcification in the Stony Coral, Stylophora pistillata

“…However, further physiology and molecular analyses are required to elucidate the mechanism controlling ROS-related damage. Furthermore, the increase in UV radiation results in DNA damage (Sinha and Häder, 2002;Petruseva et al, 2014), which may be the trigger for the over-representation of "DNA repair" terms during the night as observed here and previously suggested in the Hydra (Barve et al, 2021).…”

Hydra’s Lasting Partnership with Microbes: The Key for Escaping Senescence?

“…Looking at the DNA repair mechanisms, Hydra is not much different from other animals. Hydra genes encoding DNA repair pathways matched confidently with their vertebrate orthologues, indicating conservation at the level of sequence, structure, and function [36]. When genomic DNA of UV-exposed Hydra was checked for repair of cyclobutane pyrimidine dimers (CPDs) [36], most of the CPDs were found to be repaired by 72 h, confirming that Hydra repairs damaged DNA.…”

“…Hydra genes encoding DNA repair pathways matched confidently with their vertebrate orthologues, indicating conservation at the level of sequence, structure, and function [36]. When genomic DNA of UV-exposed Hydra was checked for repair of cyclobutane pyrimidine dimers (CPDs) [36], most of the CPDs were found to be repaired by 72 h, confirming that Hydra repairs damaged DNA. A high expression level of DNA repair protein XPF in the multipotent gamete-producing interstitial stem cells and the presence of the base excision repair (BER) and nucleotide excision repair (NER) pathway point to an effective toolbox for DNA repair and maintenance of genome integrity.…”

Involvement of Nucleotide Excision Repair and Rec-Dependent Pathway Genes for UV Radiation Resistance in Deinococcus irradiatisoli 17bor-2

“…The NER pathway, which is highly conserved among organisms from bacteria to humans, plays a crucial role in this context [ 16 ]. NER (nucleotide excision repair) primarily focuses on fixing severe DNA distortions that disrupt the helical structure of the molecule, including those produced by UV radiation.…”