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In Tunisia, drought stress is a major environmental factor limiting crop production and causing relatively low and unstable faba bean yields. In the present study, we explored the putative role of spermidine (0.5, 1, 1.5 and 2 mM) in ameliorating the effects of drought stress induced by polyethylene glycol (PEG-6000, −0.58 MPa) in faba bean seedlings. Drought stress reduced photosynthetic performance, chlorophyll and relative water content in leaves of faba bean variety Badii. Moreover, drought increased proline, electrolyte leakage and malondialdehyde content by inducing reactive oxygen species (hydrogen peroxide) generation in leaves. However, applying spermidine increased the activities of catalase, superoxide dismutase, ascorbate peroxidase and guaiacol peroxidase. The results show that the application of spermidine especially at a rate of 1.5 mM effectively reduces oxidative damage and alleviates negative effects caused by drought stress. In addition, exogenous spermidine increased the expression of polyamine biosynthetic enzymes’ genes (VfADC, VfSAMDC and VfSPDS), and reduced the expression of VfSPMS suggesting that exogenous spermidine can regulate polyamines’ metabolic status under drought challenge, and consequently may enhance drought stress tolerance in faba bean. Real-time quantitative polymerase chain reaction analysis revealed that some drought responsive genes (VfNAC, VfHSP, VfNCED, VfLEA, VfCAT, VfAPX, VfRD22, VfMYB, VfDHN, VfERF, VfSOD and VfWRKY) from various metabolic pathways were differentially expressed under drought stress. Overall, these genes were more abundantly transcribed in the spermidine-treated plants compared to untreated suggesting an important role of spermidine in modulating faba bean drought stress response and tolerance.

Drought and salinity are the most important environmental constraints affecting faba bean (Vicia faba L.) development and crop yield in Tunisia and other Mediterranean countries. Through using different strategies, associating in silico analysis of gene expression and qRT-PCR, this study aims at identifying key genes of faba bean molecular pathways potentially involved in salt and drought response. The impact of these stresses on several physiological and biochemical parameters were investigated in two genotypes (Bachar and Giza 3). To uncover abiotic stress-related genes and better understand the mechanisms of salt and drought stress tolerance in faba bean, a total of 25 faba bean genes were identified through in silico analysis. These genes were associated with important cellular processes such as transcription regulation, signal transport, kinases, phytohormonal signaling, and defense/stress responses. Most of the studied candidates were expressed at various levels in different organs including leaves, roots, flowers, stems, cotyledons, and seeds suggesting a potential role in the growth and development of faba bean plants. Furthermore, qRT-PCR was used to study gene expression profiles in leaves and roots of Bachar and Giza 3 plants under salt and drought stresses, and ABA treatment. The results showed that selected transcripts were differentially expressed under various treatments in both genotypes suggesting their important roles in abiotic stress tolerance responses. The osmotic-responsive genes identified in this study may be considered as potential candidates with a further application as stress selection markers for the creation of faba bean stress-tolerant varieties in various breeding programs. KeywordsIn silico analysis • Faba bean • Gene expression • Osmotic stress • qRT-PCR • Salt stress Communicated by B. Zheng.

Proteomic analysis was performed to investigate the differentially abundant proteins (DAPs) in barley roots during the tillering stage. Bioinformatic tools were used to interpret the biological function, the pathway analysis and the visualisation of the network amongst the identified proteins. A total of 72 DAPs (33 upregulated and 39 downregulated) among a total of 2580 proteins were identified in response to compost treatment, suggesting multiple pathways of primary and secondary metabolism, such as carbohydrates and energy metabolism, phenylpropanoid pathway, glycolysis pathway, protein synthesis and degradation, redox homeostasis, RNA processing, stress response, cytoskeleton organisation, and phytohormone metabolic pathways. The expression of DAPs was further validated by qRT-PCR. The effects on barley plant development, such as the promotion of root growth and biomass increase, were associated with a change in energy metabolism and protein synthesis. The activation of enzymes involved in redox homeostasis and the regulation of stress response proteins suggest a protective effect of compost, consequently improving barley growth and stress acclimation through the reduction of the environmental impact of productive agriculture. Overall, these results may facilitate a better understanding of the molecular mechanism of compost-promoted plant growth and provide valuable information for the identification of critical genes/proteins in barley as potential targets of compost.

Composts are an emerging biofertilizers used in agronomy that can improve crop performance, but much less is known regarding their modes of action. The current study aimed to investigate the differentially abundant proteins (DAPs) in barley leaves associated with growth promotion induced by application of date palm waste compost. Morphophysiological measurements revealed that compost induced a significant increase in plant height, chlorophyll content, gas exchange parameters and plant biomass. LC-MS/MS analyses indicate that compost induced global changes in the proteome of barley leaves. A total of 62 DAPs (26 upregulated and 36 downregulated) among a total of 2233 proteins were identified in response to compost application. The expression of DAPs was further validated based on qRT-PCR. Compost application showed altered abundance of several proteins related to abiotic stress, plant defense, redox homeostasis, transport, tricarboxylic acid cycle, carbohydrate, amino acid, energy and protein metabolism. Furthermore, proteins related to metabolic processes of phytohormone, DNA methylation and secondary metabolites were induced. These results indicate that barley responds to compost application by complex metabolism pathways and may result in a positive alteration in a physiological and metabolic barley plant state which consequently could lead to improved growth and stress adaptation observed in compost-treated plants.