Abstract

Aluminum (Al) toxicity is a significant challenge for plant growth and productivity in acid soils, which comprise nearly half of the world's arable land. To combat Al stress, plants have evolved various tolerance mechanisms. Rye (Secale cereale L.) is one of the most Al-resistant cereals, largely due to its ability to exude organic acids, such as citrate and malate, from its roots. This study explores the role of the mitochondrial fumarase gene (mFUM) in Al-induced stress in rye and other Secale species, as well as in Brachypodium distachyon, a model grass. We isolated mFUM genes from two B. distachyon lines-Al-tolerant ABR8 and Al-sensitive ABR1 (BdFUM)-and from three S. cereale cultivars (Al-tolerant Ail & eacute;s, Petkus, and Imperial; ScFUM) and an Al-sensitive inbred line of S. cereale (Riodeva). Both BdFUM and ScFUM consist of 17 exons and 16 introns, with the ScFUM gene mapped to chromosome 4R in rye. Phylogenetic analysis confirmed that ScFUM is orthologous to other mitochondrial fumarase genes in the Poaceae family. Expression analysis revealed higher levels of BdFUM and ScFUM mRNAs in roots compared to leaves, with Al-tolerant lines showing elevated expression levels in both treated and untreated plants. Additionally, mFUM expression was repressed in response to Al stress in the roots of both tolerant and sensitive lines, suggesting a complex regulatory mechanism involving multiple genes from the tricarboxylic acid cycle in response to Al toxicity. These findings enhance our understanding of the Al tolerance molecular mechanisms in cereals and the development of resilient crop varieties.