Transcriptome Analysis Reveals Dynamic Cultivar-Dependent Patterns of Gene Expression in Potato Spindle Tuber Viroid-Infected Pepper

Potato spindle tuber viroid (PSTVd) infects various plants. PSTVd pathogenesis is associated with interference with the cellular metabolism and defense signaling pathways via direct interaction with host factors or via the transcriptional or post-transcriptional modulation of gene expression. To better understand host defense mechanisms to PSTVd infection, we analyzed the gene expression in two pepper cultivars, Capsicum annuum Kurtovska kapia (KK) and Djulunska shipka (DS), which exhibit mild symptoms of PSTVd infection. Deep sequencing-based transcriptome analysis revealed differential gene expression upon infection, with some genes displaying contrasting expression patterns in KK and DS plants. More genes were downregulated in DS plants upon infection than in KK plants, which could underlie the more severe symptoms seen in DS plants. Gene ontology enrichment analysis revealed that most of the downregulated differentially expressed genes in both cultivars were enriched in the gene ontology term photosynthesis. The genes upregulated in DS plants fell in the biological process of gene ontology term defense response. We validated the expression of six overlapping differentially expressed genes that are involved in photosynthesis, plant hormone signaling, and defense pathways by quantitative polymerase chain reaction. The observed differences in the responses of the two cultivars to PSTVd infection expand the understanding of the fine-tuning of plant gene expression that is needed to overcome the infection

High-temperature effect on genes engaged in DNA methylation and affected by DNA methylation in Arabidopsis

© 2015 Elsevier Masson SAS. Along with its essential role in the maintenance of genome integrity, DNA methylation takes part in regulation of genes which are important for plant development and stress response. In plants, DNA methylation process can be directed by small RNAs in process known as RNA-directed DNA methylation (RdDM) involving two plant-specific RNA polymerases - PolIV and PolV. The aim of the present study was to investigate the effect of heat stress on the expression of genes encoding key players in DNA methylation - DNA methyltransferase (MET1, CMT3, and DRM2), the largest subunits of PoIIV and PolV (NRPD1 and NRPE1 respectively) and the DNA demethylase ROS1. We also examined the high-temperature effect on two protein-coding genes - At3g50770 and At5g43260 whose promoters contain transposon insertions and are affected by DNA-methylation, as well as on the AtSN1, a SINE-like retrotransposon. To assess the involvement of PolIV and PolV in heat stress response, the promoter methylation status and transcript levels of these genes were compared between wild type and double mutant lacking NRPD1 and NRPE1. The results demonstrate coordinated up-regulation of the DRM2, NRPD1 and NRPE1 in response to high temperature and suggest that PolIV and/or PolV might be required for the induction of DRM2 expression under heat stress. The ROS1 expression was confirmed to be suppressed in the mutant lacking active PolIV and PolV that might be a consequence of abolished DNA methylation. The increased expression of At3g50770 in response to elevated temperature correlated with reduced promoter DNA methylation, while the stress response of At5g43260 did not show inverse correlation between promoter methylation and gene expression. Our results also imply that PolIV and/or PolV could regulate gene expression under stress conditions not only through RdDM but also by acting in other regulatory processes

Transposon-associated polymorphisms of stress-responsive gene promoters in selected accessions of Arabidopsis thaliana

Genetic diversity caused by transposable element movement can play an important role in plant adaptation to local environments. Regarding genes, transposon-induced alleles were mostly related to gene bodies and a few of them to promoter regions. In this study, promoter regions of 9 stress-related genes were searched for transposable element insertions in 12 natural accessions of Arabidopsis thaliana. The promoter screening was performed via PCR amplification with primers designed to flank transposable element insertions in the promoter regions of the reference accession Col-0. Transposable element-associated insertion/deletion (indel) polymorphisms were identified in 7 of the 12 promoter loci across studied accessions that can be developed further as molecular markers. The transposable element absence in the promoter regions of orthologous genes in A. lyrata indicated that the insertion of these transposable elements in A. thaliana lineage had occurred after its divergence from A. lyrata. Sequence analysis of the promoter regions of CML41 (Calmodulin-like protein 41) and CHAP (chaperone protein dnaJ-related) confirmed the indel polymorphic sites in four accessions - Col-0, Wassilewskija, Shahdara, and Pirin. The observed indel polymorphism of the CHAP promoter region was associated with specific gene expression profiles in the different accessions grown at a normal and elevated temperature in a plant growth chamber. The collected data can be a starting point for gene expression profiling studies under conditions resembling the natural habitats of accessions