Caracterização de plantas de arroz mutantes no gene FRD-like em relação à homeostase de ferro e toxicidade por alumínio

Abstract

Rice is one of the most produced and consumed cereals by great part of the population. It is an excellent energy source, making it an important cereal mainly in developing countries. Regardless of whether rice adapts to different soil and climate conditions, its growth is affected by several abiotic factors, notably iron (Fe) deficiency and aluminum (Al) toxicity. Fe is an essential micronutrient that participates in several physiological processes, such as nitrogen fixation, hormone production and DNA synthesis. Plants submitted to Fe deficiency levels present two strategies: rhizosphere acidification and subsequent Fe2+ uptake, performed by most of the plants, and the release of phytosiderophores that function as Fe3+ chelators and later chelated Fe3+ uptake, used only by grasses. Al is also a limiting factor for the development of rice plants, being one of the most abundant elements on earth. The toxicity of Al manifests itself in different ways, notably in the inhibition of the root elongation that affects the uptake of water and nutrients. This reduces growth levels and increases susceptibility to environmental stressors. In this project, we selected 200 seeds of Oryza sativa ssp. japonica cv. Nipponbare and 200 seeds of a mutant lineage in the FRD-like gene. The seeds were grown under a hydroponic system for 20 days, then were submitted to different conditions: control (nutritive solution), Al excess (nutritive solution with the addition of 450 μM AlCl3) and Fe deficiency (nutritive solution without Fe added - 0 μM Fe-EDTA). After 14, 21 and 28 days of treatment, plants harvestings of the two strains began in order to analyze plant height, root length, root and shoot dry weight, total chlorophyll levels and the expression of genes related with Fe homeostasis and Al toxicity, in order to characterize physiologically and molecularly mutant rice plants in the FRD-like gene (locus Os12g0106600, a member of the MATE family) in relation to their role in the absorption and transport of Fe and in Al toxicity tolerance. After data collection and statistical analysis, it was noticed that the shoots of the wild line shows, over the 28 days, significantly higher differences in practically all different conditions. The root length stood out in the medium without Fe, with significantly higher differences in the mutant lineage. However, the root dry weight fluctuated during the 28 days, in the different media, being the wild lineage the only one that showed significantly higher differences, mainly in the control conditions. The analysis of gene expression was not carried out due to the Covid-19 pandemic that caused the laboratories closing and avoid the continuity of the project. In summary, the wild plants adapt better when subjected to Al toxicity and Fe deficiency. This research was useful to begin to understand the mechanisms of stress tolerance, Fe translocation processes and the response to Al toxicity, but the conclusion of this project will have a fundamental role in genetic improvement programs aimed at the biofortification of rice grains.

Date of Award	10 Nov 2021
Original language	Portuguese
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Raul Antonio Sperotto (Supervisor)