SEIJO Jose Guillermo
congresos y reuniones científicas
Chromosome bearing rDNA loci involved in meiotic chromosome abnormalities
SCARPIN, J.; CHALUP, L.; ROBLEDO, G; V.G. SOLÍS NEFFA; SEIJO J G
Congreso; Chromosome bearing rDNA loci involved in meiotic chromosome abnormalities; 2016
Lathyrus macrostachys (2n = 14) is a South American endemic species. An initial screening of some populations of this species showed many chromosome irregularities during meiosis in spite of the reported high stability of its karyotype. Chromosomes located outside of the metaphase plate, bridges and multiple spindles are among the most frequent irregularities observed that led to the formation of aneuploid microspores. On this basis, a population study of the meiotic behavior was conducted and FISH with 45S and 5S rDNA was used in pollen mother cells (PMC) in order to shed light on the mechanisms that cause the irregularities and the chromosomes involved in aberrant meiotic behavior. The study was conducted in 3 populations from NE Argentina. The results obtained here revealed that those chromosomes bearing either 45S or 5S rDNA loci were involved in the chromosome abnormalities observed in higher frequency than expected by chance. The 45S rDNA loci were mainly involved in the formation of bridges, while the 5S rDNA loci were associated to the chromosomes located outside of the metaphase plate, in first and second divisions. These chromosomes were further correlated with the occurrence of multiple spindles in the second division. Silver staining revealed that all additional microcells observed in tetrad stage and 88.19% of micro pollen grains had nucleoli. All the data confirm that the chromosomes with rDNA loci are involved in the generation of aneuploid pollen grains. The association between the meiotic bridges and SAT chromosomes may be related to the fact that in many instances the fibrillar center of nucleoli is formed by the rDNA genes of 4 chromatids that may remain entangled as the first division progresses, giving rise to bridges. However, to explain the relationship between the chromosomes bearing the 5S rDNA loci and the observed chromosomes located outside of the metaphase plate, more research is needed.