Estratégias de melhoramento para o menor acúmulo de arsênio em grãos de arroz irrigado

Abstract

Rice (Oryza sativa) is a staple food for more than half of the world population, a cause of concern, since its quality is being threatened by the accumulation of arsenic (As) in its grains. Arsenic is a highly toxic and carcinogenic metalloid. In nature, arsenic may be present as organic or inorganic forms. Inorganics such as arsenate and arsenite are considered to be significantly more toxic than organic ones. Among the factors that contribute to arsenic accumulation is the paddy rice cultivation system, wich is the most common, since under anaerobic conditions the mobility and bioavailability of As(III) is favored. As(III) and silicon (Si) share the same carriers and OsLSI2, responsible for both Si and As(III) efflux, plays a fundamental role in the accumulation of this element. To mitigate the problem of exposure to As through rice consumption, new cultivars that absorb and accumulate lower amounts of this element must be developed. Thus, the objective of this work was to characterize rice genotypes for the accumulation of arsenic in grains and to perform the OsLsi2 gene edition. The characterization of 93 rice genotypes of the japonica and indica subspecies were carried out in order to observe the accumulation of arsenic in both brown and polished (white) grains. The accumulation of arsenic in the grains were obtained through the use of inductively coupled plasma mass spectrometry (ICPMS). The genotypes Basmati 370, BRS Querencia, EMPASC 101, EMPASC 104, EMPASC 105, IRGA 424 CL, IRAT 124, IRGA 420, Jasmine 85, SC 173, SC 460, SCS 112, SCS 117 CL, SCS 114 AndoSan and Tetep presented the lowest levels of arsenic and are indicated to be used in breeding programs to obtain genotypes with low accumulation of this element. To interrupt the efflux of arsenic in rice plants, the OsLsi2 gene was edited. The CRISPR / Cas9 system was the tool used for the editing attempt. The transformation of the rice plants was indirectly made trough infection by Agrobacterium tumefaciens.The CRISPR/Cas9:OsLsi2 construct was inserted into Agrobacterium tumefaciens and subsequently these were used to infect 310 mesocotyls. PCR will be tested 51 possibly transformed plants to confirm the insertion of the CRISPR/Cas9:OsLsi2 construct.