DNA sizing, composition and origin of induced micronuclei of Zea mays L.

• Ano de defesa: 2021
• Autor(a) principal: Tostes, Nathália Vállery
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Milho - Melhoramento genético; Mutagênese; Sequenciamento de nucleotídeo; Micromanipulação; DNA
• Link de acesso: https://locus.ufv.br//handle/123456789/28757

Micronuclei (MN) are constituted of chromatin, which originated from DNA damages induced by mutagens. The mutagens promote a clastogenic effect characterized by chromosome structure damage, and/or an aneugenic effect with the loss of a whole chromosome. Due to their origin, MN are distinct in relation to genomic origin and composition. In plant mutagenesis, centromeric, telomeric and rDNA sequences were identified in MN composition. We aimed to investigate the DNA sizing, composition and origin of induced Zea mays MN after methyl methanesulfonate (MMS) treatment. Using image cytometry, we showed that the MN have distinct DNA sizing, predominantly between 0.5 – 1.5 pg. These values indicated that the MN were generated from different chromosome fragments. The variability of MN composition was confirmed by fluorescence signal variation of 180-bp knob and Grande LTR-retrotransposon sequences. Therefore, these sequences, especially the Grande LTR-retrotransposon sequence that is rich in guanine, can be considered hotspots of MMS damage and, consequently, for MN formation. The different MN origins were also revealed by a probe pool produced from two individual microdissected MN. Each microdissected MN was originated from different chromosome fragments consisting of DNA sequences of all Z. mays chromosomes. Altogether, our results showed the variability of Z. mays MN from several chromosome fragments formed after MMS treatment. Therefore, our findings demonstrated the extent of the genotoxic damage promoted by MMS in Z. mays genome. We provided insights concerning the structure of MN and methodologies that can be employed in plant mutagenesis research. Keywords: Mutagenesis. Maize. DNA content. Microdissection. Repetitive DNA sequences.