Hydroxyproline-rich glycoproteins (HRGPs) are one of the most complex families of macromolecules found in plants, due to the diversity of glycans decorating the protein backbone, as well as the heterogeneity of the protein backbones. While this diversity is responsible for a wide array of physiological functions associated with HRGPs, it hinders attempts for homology-based identification. Current approaches, based on identifying sequences with characteristic motifs and biased amino acid composition, are limited to prototypical sequences. Ragp is an R package for mining and analysis of HRGPs, with emphasis on arabinogalactan proteins. The ragp filtering pipeline exploits one of the HRGPs key features, the presence of hydroxyprolines which represent glycosylation sites. Main package features include prediction of proline hydroxylation sites, amino acid motif and bias analyses, efficient communication with web servers for prediction of N-terminal signal peptides, glycosylphosphatidylinositol modification sites and disordered regions and the ability to annotate sequences through hmmscan and subsequent GO enrichment, based on predicted Pfam domains. As such, ragp extends R’s rich ecosystem for high-throughput sequence data analyses. The ragp R package is available under the MIT Open Source license and is freely available to download from GitHub at: https://github.com/missuse/ragp.

Chicory (Cichorium intybus L.) produces bitter sesquiterpene lactones (STLs). Some enzymes in the biosynthetic pathway towards these compounds have been characterized.However, the genomic organization and tissue specificity of their biosynthesis is largely unknown. Concentrations of two sesquiterpene lactones and expression of genes involved in the first dedicated biosynthetic step were measured in different chicory tissues. BAC clones containing different genes encoding germacrene A synthase were sequenced, and revealed several tightly linked paralogs. Promoters of genes encoding two germacrene A synthases were fused to GFP and expressed in plants regenerated from transformed chicory hairy root cultures. Highest expression was observed in the epidermis of leaves and external root tissue. This work opens the possibility to select for chicory germplasm diversified in STL content, and to study their role in chicory in defence and physiology.

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ᮀ Herbicide phosphinothricin (PPT) inhibits glutamine synthetase (GS), a key enzyme in nitrogen assimilation, thus causing ammonia accumulation, glutamine depletion and eventually plant death. However, the growth response of Lotus corniculatus L. plants immersed in solutions with a broad range of PPT concentrations is biphasic, with pronounced stimulating effect on biomass production at concentrations ≤ 50 μM and growth inhibition at higher concentrations. The growth stimulation at low PPT concentrations is a result of activation of chloroplastic isoform GS2, while the growth suppression is caused by inhibition of both cytosolic GS1 and GS2 at higher PPT concentrations. Since the results are obtained in cell-free system (e.g. protein extracts), to which the principles of homeostasis are not applicable, this PPT effect is an unambiguous example of direct stimulation hormesis. A detailed molecular mechanism of concentration-dependent interaction of both PPT and a related GS inhibitor, methionine sulfoximine, with GS holoenzymes is proposed. The mechanism is in concurrence with all experimental and literature data.

Salt demonstrates various osmotic and ionic effects on vascular plant growth, development and function, but very few data can be found on how salt affects non-tracheophytes. To explore this, gametophytes of two moss – Bryum argenteum Hedw. and Atrichum undulatum (Hedw.) P. Beauv., and three fern species – Asplenium viride Britton, Ceterach officinarum DC, and Phyllitis scolopendrium (L.) Newman, were treated for 3 days with different NaCl concentrations in growth medium under in vitro controlled conditions. Subsequently, these plants recovered for 18 days on NaCl-free medium, after which the following parameters were measured for mosses: presence of secondary protonema and shoots, protonemal radius and index of multiplication. Survival, chlorophyll a, b, total and a/b ratio were determined as well as total phenolic content, both for ferns and mosses. All species tolerated 50 and 100 mM of NaCl-enriched media, quite well. On higher salt concentrations in the substrata, measured morphological parameters and chlorophyll content were reduced. In general, mosses exhibited higher NaCl tolerance than ferns. Change of phenolic content in ferns suggests these plants use antioxidative properties of phenolics as a mechanism of salt tolerance, in contrast with mosses whose phenolic content was stable.