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Cucumber mosaic cucumovirus (CMV) is a deadly plant virus that results in crop-yield losses with serious economic consequences. In recent years, environmentally friendly components have been developed to manage crop diseases as alternatives to chemical pesticides, including the use of natural compounds such as glycine betaine (GB) and chitosan (CHT), either alone or in combination. In the present study, the leaves of the cucumber plants were foliar-sprayed with GB and CHT—either alone or in combination—to evaluate their ability to induce resistance against CMV. The results showed a significant reduction in disease severity and CMV accumulation in plants treated with GB and CHT, either alone or in combination, compared to untreated plants (challenge control). In every treatment, growth indices, leaf chlorophylls content, phytohormones (i.e., indole acetic acid, gibberellic acid, salicylic acid and jasmonic acid), endogenous osmoprotectants (i.e., proline, soluble sugars and glycine betaine), non-enzymatic antioxidants (i.e., ascorbic acid, glutathione and phenols) and enzymatic antioxidants (i.e., superoxide dismutase, peroxidase, polyphenol oxidase, catalase, lipoxygenase, ascorbate peroxidase, glutathione reductase, chitinase and β-1,3 glucanase) of virus-infected plants were significantly increased. On the other hand, malondialdehyde and abscisic acid contents have been significantly reduced. Based on a gene expression study, all treated plants exhibited increased expression levels of some regulatory defense genes such as PR1 and PAL1. In conclusion, the combination of GB and CHT is the most effective treatment in alleviated virus infection. To our knowledge, this is the first report to demonstrate the induction of systemic resistance against CMV by using GB.

Root Hairs (RHs) growth is influenced by endogenous and by external environmental signals that coordinately regulate its final cell size. We have recently determined that RH growth was unexpectedly boosted when Arabidopsis thaliana seedlings are cultivated at low temperatures. It was proposed that RH growth plasticity in response to low temperature was linked to a reduced nutrient availability in the media. Here, we explore the molecular basis of this RH growth response by using a Genome Wide Association Study (GWAS) approach using Arabidopsis thaliana natural accessions. We identify the poorly characterized PEROXIDASE 62 (PRX62) and a related protein PRX69 as key proteins under moderate low temperature stress. Strikingly, a cell wall protein extensin (EXT) reporter reveals the effect of peroxidase activity on EXT cell wall association at 10 °C in the RH apical zone. Collectively, our results indicate that PRX62, and to a lesser extent PRX69, are key apoplastic PRXs that modulate ROS-homeostasis and cell wall EXT-insolubilization linked to RH elongation at low temperature. Arabidopsis root hair growth is enhanced at low temperatures. Here the authors show that the class III peroxidases PRX62 and PRX69 modulate ROS homeostasis and cell wall characteristics, and promote root hair elongation at low temperature.

Melatonin is a pleiotropic signal molecule that plays critical roles in regulating plant growth and development, as well as providing physiological protections against various environmental stresses. Nonetheless, the mechanisms for melatonin-mediated pollen thermotolerance remain largely unknown. In this study, we report that irrigation treatment with melatonin (20 µM) effectively ameliorated high temperature-induced inactivation of pollen and inhibition of pollen germination in tomato (Solanum lycopersicum) plants. Melatonin alleviated reactive oxygen species production in tomato anthers under high temperature by the up-regulation of the transcription and activities of several antioxidant enzymes. Transmission electron micrograph results showed that high temperature-induced pollen abortion is associated with a premature degeneration of the tapetum cells and the formation of defective pollen grains with degenerated nuclei at the early uninuclear microspore stage, whilst melatonin protected degradation of organelles by enhancing the expression of heat shock protein genes to refold unfolded proteins and the expression of autophagy-related genes and formation of autophagosomes to degrade denatured proteins. These findings suggest a novel function of melatonin to protect pollen activity under high temperature and support the potential effects of melatonin on reproductive development of plants.

As one of the largest gene families, F-box domain proteins have been found to play important roles in abiotic stress responses via the ubiquitin pathway. TaFBA1 encodes a homologous F-box protein contained in E3 ubiquitin ligases. In our previous study, we found that the overexpression of TaFBA1 enhanced drought tolerance in transgenic plants. To investigate the mechanisms involved, in this study, we investigated the tolerance of the transgenic plants to oxidative stress. Methyl viologen was used to induce oxidative stress conditions. Real-time PCR and western blot analysis revealed that TaFBA1 expression was up-regulated by oxidative stress treatments. Under oxidative stress conditions, the transgenic tobacco plants showed a higher germination rate, higher root length and less growth inhibition than wild type (WT). The enhanced oxidative stress tolerance of the transgenic plants was also indicated by lower reactive oxygen species (ROS) accumulation, malondialdehyde (MDA) content and cell membrane damage under oxidative stress compared with WT. Higher activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POD), were observed in the transgenic plants than those in WT, which may be related to the upregulated expression of some antioxidant genes via the overexpression of TaFBA1. In others, some stress responsive elements were found in the promoter region of TaFBA1, and TaFBA1 was located in the nucleus, cytoplasm and plasma membrane. These results suggest that TaFBA1 plays an important role in the oxidative stress tolerance of plants. This is important for understanding the functions of F-box proteins in plants' tolerance to multiple stress conditions.

Background Class Ⅲ peroxidases (PODs) are widely involved in multiple physiological processes, including lignin biosynthesis and stress responses. However, there are no reports on the identification and function of POD family in Hippophae rhamnoides subsp. sinensis Rousi. Results In this study, we identified 71 non-redundant HrPODs . Based on phylogenetic analysis, these genes were classified into 7 subgroups. Then, we analyzed the conserved domains of HrPODs proteins and found that they contain highly conserved domain. We also investigated their expression patterns in three developmental stages of sea buckthorn fruit, and the results showed that most of them were highly expressed in early stage. The GO and KEGG functional enrichment analysis showed that they widely involved in oxidative stress response and phenylpropanoid biosynthesis, respectively. According to the Pearson correlation analysis of HrPODs expression with lignin content and peroxidase activity, we further screened five HrPODs that may be involved in fruit texture quality by regulating lignin biosynthesis during fruit development. Sea buckthorn is usually distributed in arid areas with higher salt and alkaline content, and our findings showed that the different degrees of drought, salt, or alkali treatment can also affect the expression of these genes and lignin content during the germination stage. These results will help us better investigate the role of HrPODs in lignin biosynthesis to provide certain theoretical foundation in ideal berry breeding and broad spectrum stress resistance in cultivated sea buckthorn. Conclusion In this study, the findings not only provide us with a comprehensive identification and analysis of HrPODs from a bioinformatics perspective, but also preliminary intimation that the POD family may be tightly associated with fruit texture quality and abiotic stress response. These results will help us better investigate the role of HrPODs in lingin biosynthesis, enrich the theoretical research on the formation of sea buckthorn texture quality and understand the roles of HrPODs in abiotic stress resistance in cultivated sea buckthorn.

Oxidative stress and the antioxidant response induced by high environmental ammonia (HEA) were investigated in the liver and gills of three freshwater teleosts differing in their sensitivities to ammonia. The highly ammonia-sensitive salmonid Oncorhynchus mykiss (rainbow trout), the less ammonia sensitive cyprinid Cyprinus carpio (common carp) and the highly ammonia-resistant cyprinid Carassius auratus (goldfish) were exposed to 1 mM ammonia (as NH4HCO3) for 0 h (control), 3 h, 12 h, 24 h, 48 h, 84 h and 180 h. Results show that HEA exposure increased ammonia accumulation significantly in the liver of all the three fish species from 24 h-48 h onwards which was associated with an increment in oxidative stress, evidenced by elevation of xanthine oxidase activity and levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA). Unlike in trout, H2O2 and MDA accumulation in carp and goldfish liver was restored to control levels (84 h-180 h); which was accompanied by a concomitant increase in superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase activity and reduced ascorbate content. Many of these defence parameters remained unaffected in trout liver, while components of the glutathione redox cycle (reduced glutathione, glutathione peroxidase and glutathione reductase) enhanced to a greater extent. The present findings suggest that trout rely mainly on glutathione dependent defensive mechanism while carp utilize SOD, CAT and ascorbate as anti-oxidative sentinels. Hepatic cells of goldfish appear to utilize each of these protective systems, and showed more effective anti-oxidative compensatory responses towards HEA than carp, while trout were least effective. The present work also indicates that HEA exposure resulted in a relatively mild oxidative stress in the gills of all three species. This probably explains the almost complete lack of anti-oxidative responses in branchial tissue. This research suggests that oxidative stress, as well as the antioxidant potential clearly differ between salmonid and cyprinid species.

The conversion of lignocellulosic biomass into bioethanol or biochemical products requires a crucial pretreatment process to breakdown the recalcitrant lignin structure. This research focuses on the isolation and characterization of a lignin-degrading bacterial strain from a decaying oil palm empty fruit bunch (OPEFB). The isolated strain, identified as S treptomyces sp. S6, grew in a minimal medium with Kraft lignin (KL) as the sole carbon source. Several known ligninolytic enzyme assays were performed, and lignin peroxidase (LiP), laccase (Lac), dye-decolorizing peroxidase (DyP) and aryl-alcohol oxidase (AAO) activities were detected. A 55.3% reduction in the molecular weight (Mw) of KL was observed after 7 days of incubation with Streptomyces sp. S6 based on gel-permeation chromatography (GPC). Gas chromatography-mass spectrometry (GC-MS) also successfully highlighted the production of lignin-derived aromatic compounds, such as 3-methyl-butanoic acid, guaiacol derivatives, and 4,6-dimethyl-dodecane, after treatment of KL with strain S6. Finally, draft genome analysis of Streptomyces sp. S6 also revealed the presence of strong lignin degradation machinery and identified various candidate genes responsible for lignin depolymerization, as well as for the mineralization of the lower molecular weight compounds, confirming the lignin degradation capability of the bacterial strain.

Drought tolerance is a complex trait in plants that involves different biochemical mechanisms. During two years of study (2019–2020), the responses of 64 arugula genotypes to drought stress were evaluated in a randomized complete block design with three replications under field conditions. Several metabolic traits were evaluated, i.e. relative water content, photosynthetic pigments (chlorophyll and carotenoids), proline, malondialdehyde, enzymatic antioxidants (catalase, ascorbate peroxidase, and peroxidase), total phenolic and flavonoid contents and seed yield. On average, the drought stress significantly increased the proline content (24%), catalase (42%), peroxidase (60%) and malondialdehyde activities (116%) over the two years of study. As a result of the drought stress, the seed yield (18%), relative water content (19.5%) and amount of photosynthetic pigments (chlorophyll and carotenoids) dropped significantly. However, the total phenolic and flavonoid contents showed no significant changes. Under drought stress, the highest seed yields were seen in the G 50 , G 57 , G 54 , G 55 and G 60 genotypes, while the lowest value was observed in the G 16 genotype (94 g plant −1 ). According to the findings, when compared to the drought-sensitive genotypes, the drought-tolerant arugula genotypes were marked with higher levels of proline accumulation and antioxidant enzyme activity. Correlation analysis indicated the positive effects of peroxidase, catalase and proline on seed yield under drought conditions. These traits can be considered for the selection of drought-tolerant genotypes in breeding programs.

The elucidation of heat tolerance mechanisms is required to combat the challenges of global warming. This study aimed to determine the antioxidant enzyme responses to heat stress, at the enzymatic activity and gene expression levels, and to investigate the antioxidative alterations associated with heat tolerance in the stems and roots of squashes using three genotypes differing in heat tolerance. Plants of heat-tolerant “C. moschata”, thermolabile “C. maxima” and moderately heat-tolerant interspecific inbred line “Maxchata” genotypes were exposed to moderate (37 °C) and severe (42 °C) heat shocks. “C. moschata” exhibited comparatively little oxidative damage, with the lowest hydrogen peroxide (H2O2), superoxide (O2−) and malondialdehyde (MDA) contents in the roots compared to stems, followed by “Maxchata”. The enzyme activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POD) were found to be increased with heat stress in tolerant genotypes. The significant inductions of FeSOD, MnSOD, APX2, CAT1 and CAT3 isoforms in tolerant genotypes suggested their participation in heat tolerance. The differential isoform patterns of SOD, APX and CAT between stems and roots also indicated their tissue specificity. Furthermore, despite the sequence similarity of the studied antioxidant genes among “C. maxima” and “Maxchata”, most of these genes were highly induced under heat stress in “Maxchata”, which contributed to its heat tolerance. This phenomenon also indicated the involvement of other unknown genetic and/or epigenetic factors in controlling the expression of these antioxidant genes in squashes, which demands further exploration.

Selenium (Se) is a nutritional trace mineral essential for various aspects of human health that exerts its effects mainly through its incorporation into selenoproteins as the amino acid, selenocysteine. Twenty-five selenoprotein genes have been identified in humans and several selenoproteins are broadly classified as antioxidant enzymes. As progress is made on characterizing the individual members of this protein family, however, it is becoming clear that their properties and functions are quite diverse. This review summarizes recent insights into properties of individual selenoproteins such as tissue distribution, subcellular localization, and regulation of expression. Also discussed are potential roles the different selenoproteins play in human health and disease.