Department of Plant Sciences

The apoplast is known to play a predominant role in the expression of manganese (Mn) toxicity in cowpea (Vigna unguiculata [L.] Walp). The initial rapid symplastic molecular changes leading to Mn tolerance or triggering proteomic and metabolomic apoplastic processes leading to Mn toxicity in cowpea are currently poorly understood. Therefore, the focus was on the identification of early excess Mn-induced genotypic differences in the leaf-gene expression of the Mn-tolerant cowpea cv. TVu 1987 and the Mn-sensitive cowpea cv. TVu 91. Furthermore, the beneficial mineral element silicon (Si), known to improve Mn tolerance in plants, was included in the experiments in order to detect modifications in gene expression leading to enhanced Si-mediated Mn tolerance in the Mn-sensitive cowpea genotype. Thus, the PCR-based Suppression Subtractive Hybridization technique (SSH) enabled a creation of cultivar and treatment specific subtractive cDNA libraries. The results showed that short-term elevated Mn supply induced large-scale changes in the transcriptome of both cowpea cultivars. Furthermore, the coexistence of a Mn-combined but also broad constitutive impact of Si on the transcriptome level could be demonstrated for the Mn-sensitive cowpea gentoype. These results call for a more in-depth analysis of genotypic differences in the excess Mn response on the transcriptome level including a comprehensive selection of further candidate genes. Therefore, an expanded transcriptomic assay, including the selection of differentially expressed candidate genes and the investigation of their genotype specific expression pattern by quantitative Real-Time PCR (qRT-PCR), might reveal further insights into the symplastic processes triggering Mn tolerance through apoplastic processes in cowpea.