Polyamines mitigate the destructive impacts of salinity stress by enhancing photosynthetic capacity, antioxidant defense system and upregulation of calvin cycle-related genes in rapeseed (Brassica napus L.).

Salinity is widespread environmental stress that poses great obstacles to rapeseed development and growth. Polyamines are key plant growth regulators that play a pivotal role in regulating salt tolerance. Rapeseed (Brassica napus L.) seedlings were treated by spermine (Spm) and spermidine (Spd) versus untreated control under salt stress conditions. It was detected that the Spd-treated plants had significantly elevated chlorophyll and proline content and maintained higher photosystem II (PSII) activity than those treated with Spm as well as untreated control under salt-stressed conditions. Similarly, Spd alleviated the devastating effects of NaCl stress on CO2 assimilation and significantly elevated Rubisco activity (ribulose 1,5-bisphosphate carboxylase/oxygenase). The application of Spd also enhanced the activities of different antioxidant enzymes under NaCl stress. It modulated their respective transcription levels, including ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), and dehydroascorbate reductase (DHAR). In addition, exogenously sprayed Spd enhanced the polyamine pathway as observed by upregulated transcription of polyamine oxidase (PAO) and diamine oxidase (DAO). The Spd application enhanced expressions of Calvin cycle enzyme related genes such as Rubisco small subunit, Rubisco large subunit, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), 3-phosphoglyceric acid kinase (PGK), triose-3-phosphate isomerase (TPI), fructose-1,6-bisphosphate aldolase (FBA), sedoheptulose-1,7-bisphosphatase (SBPase), and fructose-1,6-bisphosphate phosphatase (FBPase). Consequently, this study demonstrates that exogenous application of Spd has a valuable role in regulating antioxidant enzyme activity, polyamine pathway, and Calvin cycle enzyme-related genes to alleviate salt stress damage in the plants.

Exogenous melatonin enhances the reactive oxygen species metabolism, antioxidant defense-related gene expression, and photosynthetic capacity of Phaseolus vulgaris L. to confer salt stress tolerance.

Melatonin (MT) has been reported to regulate certain plant physiological processes and promote tolerance to different environmental stresses such as salinity. Green bean (Phaseolus vulgaris L. cv. Royal Nel) seedlings were exposed to 200 mM NaCl with or without pre-treatment with 150 µM MT. Salt stress led to a lower chlorophyll content, a reduced photosynthetic activity, increased reactive oxygen species (ROS) contents, and decreased photosystem II (PSII) activity. The application of exogenous MT to green bean seedlings under salt stress improved photosynthetic activity and alleviated the oxidative damages by enhancing the activity of antioxidant enzymes. The expression of catalase (CAT1), glutathione reductase (GR), superoxide dismutase (CuZnSOD1), ascorbate peroxidase (APX), Peroxiredoxin Q (PrxQ), and 2-cysteine peroxiredoxin (2-Cys-Prx) encoding genes was significantly increased under salt stress in green bean seedling compared with the untreated control. However, plants treated with exogenous MT and NaCl had 28.8, 21.1, 26.1, 20, 26.2, and 22.4% higher CuZnSOD, CAT1, APX, GR, PrxQ, and 2-Cys-Prx transcript levels, respectively, compared to NaCl stress alone. Our study revealed the protective mechanisms mediated by exogenous MT application in NaCl stress alleviation and our findings could be used in the management of green bean cultivation in salinity-prone soils.

Investigating molecular evolutionary forces and phylogenetic relationships among melatonin precursor-encoding genes of different plant species.

A total of 53 plant species accessions from different geographic regions, including four melatonin precursor-coding genes obtained from Arachis hypogaea (ASMT1, 2, 3 and T5H) underwent extensive molecular evolutionary analyses. Evolutionary relationships were inferred and showed that dichotomous bifurcating trees did not reflect the true phylogeny since reticulate events took place due likely to recombination. Thus, a phylogenetic network was reconstructed for each type of enzyme and highlighted the presence of such incompatibilities. GARD algorithm pointed out that ASMT1, 2, and 3-coding gene sequences contained recombination sites with significant topological incongruence on both sides of the breakpoints (for ASMT1, and 2), while only on one side of the breakpoints for ASMT3. In contrast, no statistically recombination signal was recorded in T5H-coding gene. Furthermore, gene duplication was localized in the ancestor of a monophyletic group of Populus accessions. Selection pressure was assessed using several statistical models incorporated in HyPhy package through the datamonkey web server. It was demonstrated that numerous individual sites and tree branches experienced predominantly purifying selection. In contrast, the BUSTED model evidenced a gene-wide episodic diversifying selection in the phylogeny of only three enzyme-coding genes (ASMT, and 2, and T5H). Likewise, it was shown that Mixed Effects Model of Episodic Selection (MEME) model detected only episodic positively selected sites in all four melatonin enzymes-coding genes; whereas, REL model failed to detect neither positive nor negative selection in tested individual sites of ASMT3-coding gene.

A Proteomic Approach to Investigate the Drought Response in the Orphan Crop Eragrostis tef.

The orphan crop, Eragrostis tef, was subjected to controlled drought conditions to observe the physiological parameters and proteins changing in response to dehydration stress. Physiological measurements involving electrolyte leakage, chlorophyll fluorescence and ultra-structural analysis showed tef plants tolerated water loss to 50% relative water content (RWC) before adverse effects in leaf tissues were observed. Proteomic analysis using isobaric tag for relative and absolute quantification (iTRAQ) mass spectrometry and appropriate database searching enabled the detection of 5727 proteins, of which 211 proteins, including a number of spliced variants, were found to be differentially regulated with the imposed stress conditions. Validation of the iTRAQ dataset was done with selected stress-related proteins, fructose-bisphosphate aldolase (FBA) and the protective antioxidant proteins, monodehydroascorbate reductase (MDHAR) and peroxidase (POX). Western blot analyses confirmed protein presence and showed increased protein abundance levels during water deficit while enzymatic activity for FBA, MDHAR and POX increased at selected RWC points. Gene ontology (GO)-term enrichment and analysis revealed terms involved in biotic and abiotic stress response, signaling, transport, cellular homeostasis and pentose metabolic processes, to be enriched in tef upregulated proteins, while terms linked to reactive oxygen species (ROS)-producing processes under water-deficit, such as photosynthesis and associated light harvesting reactions, manganese transport and homeostasis, the synthesis of sugars and cell wall catabolism and modification, to be enriched in tef downregulated proteins.

Molecular and biochemical characterisation of a novel type II peroxiredoxin (XvPrx2) from the resurrection plant Xerophyta viscosa.

A type II peroxiredoxin gene (XvPrx2) was isolated from a Xerophyta viscosa (Baker) cDNA cold-stress library. The polypeptide displayed significant similarity to other plant type II peroxiredoxins, with the conserved amino acid motif (PGAFTPTCS) proposed to constitute the active site of the enzyme. Northern blot analyses showed that XvPrx2 gene was stress-inducible in response to abiotic stresses while gel analyses revealed that XvPrx2 homologues exist within the X. viscosa proteome. Using a yellow fluorescent reporter protein, the XvPrx2 protein localised to the cytosol. A mutated protein (XvV7) was generated by converting the valine at position 76 to a cysteine and an in vitro DNA protection assay showed that, in the presence of either XvPrx2 or XvV7, DNA protection occurred. In addition, an in vivo assay showed that increased protection was conferred to Escherichia coli cells overexpressing either XvPrx2 or XvV7. The XvPrx2 activity was maximal with DTT as electron donor and H2O2 as substrate. Using E. coli thioredoxin, a 2-15-fold lower enzyme activity was observed. The XvPrx2 activity with glutathione was significantly lower and glutaredoxin had no measurable effect on this reaction. The XvV7 protein displayed significantly lower activity compared with XvPrx2 for all substrates assessed.

Boosting the globalization of plant proteomics through INPPO: current developments and future prospects.

The International Plant Proteomics Organization (INPPO) is a non-profit-organization consisting of people who are involved or interested in plant proteomics. INPPO is constantly growing in volume and activity, which is mostly due to the realization among plant proteomics researchers worldwide for the need of such a global platform. Their active participation resulted in the rapid growth within the first year of INPPO's official launch in 2011 via its website (www.inppo.com) and publication of the 'Viewpoint paper' in a special issue of PROTEOMICS (May 2011). Here, we will be highlighting the progress achieved in the year 2011 and the future targets for the year 2012 and onwards. INPPO has achieved a successful administrative structure, the Core Committee (CC; composed of President, Vice-President, and General Secretaries), Executive Council (EC), and General Body (GB) to achieve INPPO objectives. Various committees and subcommittees are in the process of being functionalized via discussion amongst scientists around the globe. INPPO's primary aim to popularize the plant proteomics research in biological sciences has also been recognized by PROTEOMICS where a section dedicated to plant proteomics has been introduced starting January 2012, following the very first issue of this journal devoted to plant proteomics in May 2011. To disseminate organizational activities to the scientific community, INPPO has launched a biannual (in January and July) newsletter entitled 'INPPO Express: News & Views' with the first issue published in January 2012. INPPO is also planning to have several activities in 2012, including programs within the Education Outreach committee in different countries, and the development of research ideas and proposals with priority on crop and horticultural plants, while keeping tight interactions with proteomics programs on model plants such as Arabidopsis thaliana, rice, and Medicago truncatula. Altogether, the INPPO progress and upcoming activities are because of immense support, dedication, and hard work of all members of the INPPO community, and also due to the wide encouragement and support from the communities (scientific and non-scientific).