Deciphering the reactive oxygen species signaling network in Arabidopsis thaliana
Using forward and reverse genetics, scientists from IMBB together with collaborators from The Netherlands (Prof. J. Hille) have isolated a number of mutants with increased tolerance or sensitivity to oxidative stress caused by the fungal AAL-toxin, aminotriazole (AT), and paraquat (PQ) (Gechev et al. 2008; Qureshi et al. 2011; Mehterov et al. 2012; Gechev, Mehterov, et al. 2013; Qureshi et al. 2013; Petrov et al. 2013).
The oxidative stress-related phenotype of two of them is shown below (Figure 1). The mutants obtained by the forward genetics approach are being cloned. High throughput transcriptional profiling (RNA-seq, multi-parallel qRT-PCR, microarrays) and metabolomics (GC-MS of primary metabolites, LC-MS of secondary metabolites) techniques are employed to unravel the processes and pathways responsible for the altered stress tolerance in these mutants and to identify downstream genes in the signaling cascade.
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In another line of research, the leaf- and tissue-specific translatomes of A. thaliana were analyzed before and after oxidative stress, using a set of transgenic Arabidopsis lines expressing a FLAG-tagged ribosomal protein to immunopurify polysome-bound mRNAs (Benina et al. 2015). The translation of 171 ROS-responsive genes mRNAs was determined for five cell types: mesophyll, bundle sheath, phloem companion, epidermal and guard cells. Cell type-specific translation patterns were detected for a number of genes, including genes encoding transcription factors, which provides insights about the cell-specific responses and functions during oxidative stress.
Molecular mechanisms of desiccation tolerance in Haberlea rhodopensis
H. rhodopensis is a desiccation-tolerant species endemic to the Balkan Peninsula (Figure 2) (Gechev, Benina, et al. 2013). In addition to extreme drought, it can withstand low temperature stress as well (Benina et al. 2013). Furthermore, dark-induced senescence is significantly delayed in this species. Physiological approaches combined with high-throughput transcriptional profiling (RNA-seq) and metabolomics (GC-MS and LC-MS) are utilized to understand the mechanisms behind these phenomena.
In addition, comparative transcriptomics and metabolomics with other model species (Arabidopsis thaliana, Thellungiella halophila) and relatives (Gloxinia perennis) are carried out (Benina et al. 2013). Recently, scientists from IMBB in collaboration with the Medical University of Plovdiv and the Max Planck Institute of Plant Physiology (Potsdam-Golm) have initiated a more detailed study of secondary metabolites in H. rhodopensis to address the observed medicinal properties of its extracts (Gechev et al. 2014).
