Perfil transcricional e regulação de genes relacionados a autofagia em plântulas de arroz cultivadas sob excesso de ferro

Abstract

Rice (Oryza sativa L.) is one of the most cultivated and consumed cereals in the world. The predominant cultivation system is by flooding, which makes iron more available for uptake, causing stress on plants and interfering with the productive potential of genotypes. Iron is an essential micronutrient for plants, however when in excess it causes toxicity. Direct toxicity occurs due to excessive absorption and subsequent accumulation of iron in plant tissues. Indirect toxicity results from the limited absorption by plants of various nutrients. Rice has two strategies for absorbing iron, strategy I is based on the reduction of ferric iron to ferrous iron and strategy II is on chelation of iron. Many studies have been developed to identify and characterize the genes that encode proteins involved in iron uptake, transport and accumulation of Fe in the plant. These studies seek to outline strategies to solve the different problems related to Fe in the plant, such as deficiency in dryland cultivation, toxicity and low accumulation of this element in the grain. In this study the focus was given to the high availability of Fe in the soil and seeks to identify and characterize new mechanisms of tolerance to Fe toxicity in rice. Autophagy is the main route of degradation and recycling of cytoplasmic material. This process is mainly involved with stress adaptation and immune response, as well as promoting programmed cell death in different situations. Recent studies have revealed the importance of autophagy in tolerance to different abiotic stresses. However, there is still no information in the literature relating autophagy to Fe toxicity. In this context, this study aimed to characterize the regulation and transcriptional activation profile of OsATG (associated with autophagy) genes in rice seedlings subjected to iron toxicity (FeT). The cultivars EPAGRI 108 (tolerant) and BR IRGA 409 (sensitive) were subjected to treatment for excess iron for five days, after shoot and root were collected. RNA was extracted, converted to cDNA and after the relative expressions of the genes OsATG3a, OsATG4a, OsATG5, OsATG7, OsATG8a, OsATG10b, OsATG12, OsATG16b and OsATG18a were evaluated, the promoters of these genes were also analyzed. OsATG genes were induced in the tolerant genotype and repressed in the sensitive genotype. In addition, OsATGs gene promoters are rich in W-box cis regulatory elements targeted by WRKYs transcription factors. These results indicate that OsATGs genes are involved in FeT response and these genes are transcriptionally regulated by WRKY transcription factors. This study provides early insights into the involvement of autophagy in FeT tolerance.