Frequency of the RAD51 (radiation sensitive 51) recombinase in species and hybrids of Brachiaria and relationship with genetic variability.
2016
PAULA, C. M. P. de | LIMA, D. C. | SOUZA SOBRINHO, F. de | TECHIO, V. H.
Abstract : This study identified and compared the frequency of homology and recombination hotspots in sexual diploid and tetraploid species, apomictic tetraploids and hybrids of Brachiaria, by immunolocalization of the radiation sensitive 51 (RAD51). Roots were fixed in 4% paraformaldehyde. We applied primary antibody (Rat anti-Arabidopsis thaliana RAD51) and detected with a secondary antibody (Goat anti-rat IgG FITC). The analysis of this protein showed diffuse signals at leptotene. In zygotene, signals of RAD51 were identified in unpaired chromosomes or partially paired and adjacent signals of RAD51 in paired chromosomes, confirming its close involvement with the search for chromosomal homology. During pachytene, RAD51 signals were located between chromosome axes in recombination hotspots. The mean number of recombination signals was greater in apomictic species of Brachiaria (B. decumbens, 85.80 and B. brizantha, 83.87), this higher frequency of signals can be related to the mode of reproduction of the species. The artificially tetraploidized B. ruziziensis showed a mean number of RAD51 signals similar the diploid B. ruziziensis, as a result of the polyploidization. The hybrids presented an overlap of the mean number of RAD51 signals compared to diploid and tetraploid of B. ruziziensis. This non-additivity of genomes is possibly an adaptation to genomic stress caused by hybridization and polyploidy.
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