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Sodium chloride (NaCl) induced expression of a jacalin-related mannose-binding lectin (JRL) gene in leaves, roots, and callus cultures of Populus euphratica (salt-resistant poplar). To explore the mechanism of the PeJRL in salinity tolerance, the full length of PeJRL was cloned from P. euphratica and was transformed into Arabidopsis. PeJRL was localized to the cytoplasm in mesophyll cells. Overexpression of PeJRL in Arabidopsis significantly improved the salt tolerance of transgenic plants, in terms of seed germination, root growth, and electrolyte leakage during seedling establishment. Under NaCl stress, transgenic plants retained K+ and limited the accumulation of Na+. PeJRL-transgenic lines increased Na+ extrusion, which was associated with the upward regulation of SOS1, AHA1, and AHA2 genes encoding plasma membrane Na+/proton (H+) antiporter and H+-pumps. The activated H+-ATPases in PeJRL-overexpressed plants restricted the channel-mediated loss of K+ that was activated by NaCl-induced depolarization. Under salt stress, PeJRL–transgenic Arabidopsis maintained reactive oxygen species (ROS) homeostasis by activating the antioxidant enzymes and reducing the production of O2− through downregulation of NADPH oxidases. Of note, the PeJRL-transgenic Arabidopsis repressed abscisic acid (ABA) biosynthesis, thus reducing the ABA-elicited ROS production and the oxidative damage during the period of salt stress. A schematic model was proposed to show the mediation of PeJRL on ABA response, and ionic and ROS homeostasis under NaCl stress. [ABSTRACT FROM AUTHOR]

Phospholipase Dα (PLDα), which produces signaling molecules phosphatidic acid (PA), has been shown to play a critical role in plants adapting to salt environments. However, it is unclear whether phospholipase Dδ (PLDδ) can mediate the salt response in higher plants. PePLDδ was isolated from salt-resistant Populus euphratica and transferred to Arabidopsis thaliana to testify the salt tolerance of transgenic plants. The NaCl treatment (130 mM) reduced the root growth and whole-plant fresh weight of wild-type (WT) A. thaliana, vector controls (VC) and PePLDδ-overexpressed lines, although a less pronounced effect was observed in transgenic plants. Under salt treatment, PePLDδ-transgenic Arabidopsis exhibited lower electrolyte leakage, malondialdehyde content and H2O2 levels than WT and VC, resulting from the activated antioxidant enzymes and upregulated transcripts of genes encoding superoxide dismutase, ascorbic acid peroxidase and peroxidase. In addition, PePLDδ-overexpressed plants increased the transcription of genes encoding the plasma membrane Na+/H+ antiporter (AtSOS1) and H+-ATPase (AtAHA2), which enabled transgenic plants to proceed with Na+ extrusion and reduce K+ loss under salinity. The capacity to regulate reactive oxygen species (ROS) and K+/Na+ homeostasis was associated with the abundance of specific PA species in plants overexpressing PePLDδ. PePLDδ-transgenic plants retained a typically higher abundance of PA species, 34:2 (16:0–18:2), 34:3 (16:0–18:3), 36:4 (18:2–18:2), 36:5 (18:2–18:3) and 36:6 (18:3–18:3), under control and saline conditions. It is noteworthy that PA species 34:2 (16:0–18:2), 34:3 (16:0–18:3), 36:4 (18:2–18:2) and 36:5 (18:2–18:3) markedly increased in response to NaCl in transgenic plants. In conclusion, we suppose that PePLDδ-derived PA enhanced the salinity tolerance by regulating ROS and K+/Na+ homeostasis in Arabidopsis. [ABSTRACT FROM AUTHOR]

Phytoremediation offers a great potential for affordable remediation of heavy metal (HM)−polluted soil and water. Screening and identifying candidate genes related to HM uptake and transport is prerequisite for improvement of phytoremediation by genetic engineering. Using the cadmium (Cd)−hypersensitive Populus euphratica , an annexin encoding gene facilitating Cd enrichment was identified in this study. With a 12 h exposure to CdCl 2 (50–100 μM), P. euphratica cells down-regulated transcripts of annexin1 (PeANN1). PeANN1 was homologue to Arabidopsis annexin1 (AtANN1) and localized mainly to the plasma membrane (PM) and cytosol. Compared with wild type and Atann1 mutant, PeANN1 overexpression in Arabidopsis resulted in a more pronounced decline in survival rate and root length after a long-term Cd stress (10 d, 50 μM), due to a higher cadmium accumulation in roots. PeANN1 −transgenic roots exhibited enhanced influx conductance of Cd2+ under cadmium shock (30 min, 50 μM) and short-term stress (12 h, 50 μM). Noteworthy, the PeANN1-facilitated Cd2+ influx was significantly inhibited by a calcium-permeable channel (CaPC) inhibitor (GdCl 3) but was promoted by 1 mM H 2 O 2 , indicating that Cd2+ entered root cells via radical-activated CaPCs in the PM. Therefore, PeANN1 can serve as a candidate gene for improvement of phytoremediation by genetic engineering. ga1 ● The Cd-sensitive P. euphratica declined annexin 1 (ANN1) transcription upon Cd stress. ● PeANN1 increased Cd accumulation in root cells of transgenic Arabidopsis. ● PeANN1 facilitated Cd2+ influx through calcium-permeable channels in the root PM. ● H 2 O 2 promotes influx of Cd2+ and calcium in transgenic roots overexpressing PeANN1. [ABSTRACT FROM AUTHOR]