Expression of OsFRDL1, a MATE gene family member, indicates its involvement in aluminum response in rice

In soils under acidic conditions, Aluminum (Al) is solubilized to its ionic form, which is toxic to plants. Al rapidly inhibits root elongation, water and nutrient uptake, resulting in crop yield reduction. Members of the MATE family are responsible for citrate transport and Al detoxification in different species. In rice, the OsFRDL1 gene (MATE family) is homologous to the HvAACT1 and SbMATE, which are involved in Al tolerance in barley and sorghum, respectively. Silencing OsFRDL1 showed that it is not involved in Al tolerance in rice. However, the OsFRDL1 expression was not accessed in rice genotypes contrasting for Al tolerance. Thus, in this study, four Brazilian rice genotypes were evaluated in response to Al treatment in different time of exposition and OsFRDL1 expression was analyzed. The analyzed cultivars displayed different responses to Al dose x time. Al affected root growth in all analyzed genotypes, however, a minor negative effect that only occurred after 72 and 48 hours of exposure was detected in Farroupilha and BRS Curinga cultivars, respectively. In contrast, BR-IRGA 410 and IAS 12-9 showed a negative effect in root growth from the first hours of exposure to Al. Two cultivars differing in Al tolerance were used for gene expression analysis. The expression of OsFRDL1 was highly increased in Al-tolerant cultivar Farroupilha than in the Al-sensitive cultivar BR IRGA 410. This results indicates that OsFRDL1 is regulated by Al. This finding suggests that OsFRDL1 is involved in Al stress response, however seems to be insufficient in controlling Al tolerance