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.
In the present study we have identified hydroxy-plastochromanol in plants for the first time. This compound was found both in low light and high light-grown Arabidopsis plants, however, under high light stress its level was considerably increased. Hydroxy-plastochromanol accumulated also during ageing of leaves of low light-grown plants, similarly as in the case of other prenyllipids. Our results indicate that hydroxy-plastochromanol found in leaves is probably formed as a result of plastochromanol oxidation by singlet oxygen generated in photosystem II during photosynthesis. These data also support the hypothesis that plastochromanol is an efficient antioxidant in vivo, similarly as tocopherols and plastoquinol.