Organization of satellite DNAs in the genome of the grasshopper Abracris flavolineata with emphasis on supernumerary chromosomes: a structural, functional, and evolutionary approach

Author(s)

Diogo Milani

• Document type: Master's Dissertation
• Press: Rio Claro. 2017-03-20.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Rio Claro
• Defense date: 2017-03-02
• Advisor: Diogo Cavalcanti Cabral de Mello

Abstract

Satellite DNAs (satDNA) are sequences usually repeated hundred to thousand times tandemly arrayed, enriched in heterochromatin from specific region or chromosomes, including B chromosomes. Here, we isolated the first satDNA in the grasshopper Abracris flavolineata, named AflaSAT-1. The sequence was characterized by integration of cytogenetic, molecular and genomics approaches, aiming to understand the structural organization, evolution in A and B chromosomes and possible transcriptional activity. The AflaSAT-1 is shared with other grasshopper species, but it was evidently amplified in A. flavolineata forming detectable clustered arrays. AflaSAT-1 presented low variability at interpopulational level; but monomers from B chromosome observed in individuals from Rio Claro/SP were more variable presenting four exclusive mutations, reflecting the common higher mutational rate in this chromosome. Genomic structural analysis revealed distinct organization for the satDNA, with its alternative association with other satDNA, named AflaSAT-2. The chromosomal analysis showed that both satDNAs were also interglimed to each other, forming large blocks in centromeres of almost all chromosomes (except the smallest pair), but in the B chromosome only a small centromeric signal was noticed in individuals from Rio Claro/SP. Chromosomal distribution for AflaSAT-1 revealed variability, at populational level, with absence of marks, additional clusters and heteromorphism. This variation was coincidentally followed by variability in copy number, suggesting dynamic expansion or elimination of repeats. Finally, AflaSAT-1 was constitutively transcriptionally active in five tissues of adults, in distinct life cycle phases, and both in carrier and non-B chromosome carriers. (AU)

• FAPESP's process: 15/05246-3 - Satellite DNA organization in the genome of the grasshopper Abracris flavolineata with emphasis in the supernumerary chromosomes: a structural, functional and evolutionary approach
• Grantee: Diogo Milani
• Support Opportunities: Scholarships in Brazil - Master