Pectin methylesterase gene and aluminum tolerance in Secale cereale

Abstract

Pectin methylesterases (PME) are involved in plant responses to abiotic stress, including aluminum (Al) tolerance in acid soils. In these lands, soluble Al (Al3+) inhibits root elongation and limits plant growth. Rye (Secale cereale L.) is one of the most Al-tolerant cereal crops. We isolated the ScPME gene, encoding a group 2 PME, in three Al-tolerant rye cultivars (Ailés, Imperial and Petkus) and one sensitive inbred rye line (Riodeva). This gene, which has two exons and one intron, was located on the long arm of chromosome 2R and encoded a putative PME with all the characteristic domains of group 2 PME proteins. Exon 1 was more variable than exon 2 among both different ryes and different Poaceae species. The phylogenetic relationships obtained using cDNA and protein sequences indicated that the ScPME protein is orthologous to other group 2 PME proteins from different Poaceae species. The Al induces the production of pectins in the root apices of tolerant Petkus but reduces it in the sensitive Riodeva. Expression of the ScPME gene occurred mainly in the roots and was very low in leaves. Moreover, the amount of this mRNA in roots not treated with Al was greater in the tolerant Petkus than in the sensitive Riodeva. ScPME mRNA levels decreased in response to Al stress in the roots of Petkus after 24h of treatment. In the case of Riodeva PME transcription was induced after 24h of stress. These results suggest that ScPME gene could be related with Al tolerance in rye.