A Spotlight on Rad52 in Cyanidiophytina (Rhodophyta):A Relic in Algal Heritage

RADiation sensitive52 (RAD52) protein catalyzes the pairing between two homologous DNA sequences double-strand break repair and meiotic recombination, mediating RAD51 loading onto single-stranded DNA ends, and initiating homologous recombination and catalyzing DNA annealing. This article reports for the first time the presence of RAD52 homologs in the thermo-acidophilic Cyanidiophyceae whose genomes have undergone extensive sequencing. Database mining, phylogenetic inference, prediction of protein structure and evaluation of gene expression were performed in order to determine the functionality of RAD52 protein in Cyanidiophyceae. Our findings support that RAD52 gene and protein have an ancient origin, though it has been subsequently lost in all green algae and land plants. Its current function in Cyanidiophytina could be related to stress damage response for thriving in hot and acidic environments as well as to the genetic variability of these algae, in which – conversely to extant Rhodophyta - sexual mating was never observed.