Transcriptomic Analysis of Transgenic Tobacco Plants Overexpressing a Mitochondrial Uncoupling Protein (UCP)

Uncoupling proteins (UCP) are mitochondrial transporters that uncouple respiration from ATP synthesis. UCPs have been show to protect plants against oxidative stress and overexpression of the Arabidopsis thaliana UCP1 (AtUCP1) in transgenic tobacco resulted in increased tolerance to different abiotic stresses. To unravel the possible molecular mechanisms associated with the improved stress tolerance of the AtUCP1-overexpressors, an RNA sequencing-based transcriptome analysis was performed using Illumina MiSeq. For this, two transgenic lines presenting different levels of AtUCP1 expression were employed. RNA-Seq generated more than 1.1 million sequence reads for each sample, which resulted in ~34.000 assembled contigs. A total of 816 differentially expressed genes were detected between the AtUCP1 lines and untransformed plants, among which 239 were up-regulated and 577 were down-regulated (p≤0.001). The up-regulated genes (fold change ≥2) were associated with different functional categories: ATP binding was dominant in the main category “molecular function”, while oxidation-reduction process /pentose-phosphate shunt were dominant in the main category “biological process”. Moreover, chloroplast envelop was prominent in the category “cellular component”. A number of stress responsive genes, especially those associated with heat, oxidative and cold stresses, were identified within the set of up-regulated genes, indicating that UCP overexpression triggers plant stress response probably through retrograde signaling.