Metabolic and physiological aspects associated with differential aluminum tolerance in maize

• Autor(a) principal: Silva, Marcelle Ferreira
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: https://locus.ufv.br//handle/123456789/28839
• topic: Milho - Genética - Efeito do alumínio; Stress (Fisiologia); Citratos; Ecofisiologia Vegetal

Maize (Zea mays) is a major crop cultivated worldwide with several uses including animal feeding human consumption and alcohol production. Notably, it is mostly cultivated in tropical and subtropical regions, where acid soils are prevalent. In those acidic soils, the toxicity triggered by aluminum (Al), in special Al 3+ , is the main factor limiting agricultural production. In this context, strategies aiming at developing stress-resistant crops could increase productive capacity and reduce yield penalty. Al tolerance in maize has been associated with organic acid (OA) exudation, mediated mainly by the membrane transporter family MATE (MULTIDRUG AND TOXIC COMPOUND EXTRUSION). Which are responsible for citrate exudation to rizosphere in an OA/H + antiport in root cells in response to Al toxicity. In this study, we used five genotypes derived from Al-intermediate tolerant (L3) and Al-sensitive (L53) genotypes with differential expression of the gene MATE that culminated with differential Al tolerance. Given that OA is intimately related with tricarboxilic acid cycle the metabolic consequences of this differential Al-tolerance were investigated. Higher Al content was observed in Al treated samples in all genotypes comparing with its respective controls. Interestingly, Al treated seedlings of tolerant genotypes showed higher increase in Al content than seedling of sensitive ones. This fact aside, higher accumulation of Al was observed in roots of genotypes with lower OA exudation. Moreover, this change in Al uptake and transport also lead to significant changes in mineral elements content including calcium and magnesium. Histochemical evaluation of hydrogen peroxide (H 2 O 2 ) and superoxide (O 2- ) in roots indicate that accumulation of those reactive oxygen species was actually higher in absence of Al and that it was similar in presence of Al for tolerant genotypes, suggesting that cell division was less affected in those genotypes. Al tolerant genotypes were characterized by minor disturbances in primary metabolism (i.e. photosynthesis and respiration) while the sensitive genotypes, with little if any OA exudation, were characterized by Al-damage effects (i.e. root and shoot growth) since the first hours of Al exposure. Although our findings indicate that different organs of the same species can present distinct Al resistance and/or tolerance mechanisms they were collectively able to provide a better understanding of the mechanisms used by maize genotypes to avoid or to minimize Al toxicity. Keywords: Citrate exudation. Abiotic stress. Root growth. ZmMATE1