As a gas signal molecule, hydrogen sulfide (H2S) can enhance plant stress resistance. Here, cucumber (Cucumis sativus ‘Xinchun NO. 4’) explants were used to investigate the role of H2S in adventitious root development under salt stress. The results show that sodium chloride (NaCl) at 10 mM produced moderate salt stress. The 100 µM sodium hydrosulfide (NaHS) treatment, a H2S donor, increased root number and root length by 38.37% and 66.75%, respectively, indicating that H2S effectively promoted the occurrence of adventitious roots in cucumber explants under salt stress. The results show that under salt stress, NaHS treatment reduced free proline content and increased the soluble sugar and soluble protein content during rooting. Meanwhile, NaHS treatment enhanced the activities of antioxidant enzymes [peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT)], increased the content of ascorbic (ASA) and glutathione (GSH), reduced the content of hydrogen peroxide (H2O2) and the rate of superoxide radical (O2−) production, and decreased relative electrical conductivity (REC) and the content of malondialdehyde (MDA). However, the NaHS scavenger hypotaurine (HT) reversed the above effects of NaHS under salt stress. In summary, H2S promoted adventitious root development under salt stress through regulating osmotic substance content and enhancing antioxidant ability in explants.
Calmodulin-binding transcription activator (CAMTA) plays an important regulatory role in plant growth, development, and stress response. This study identified the phylogenetic relationships of the CAMTA family in 42 plant species using a genome-wide search approach. Subsequently, the evolutionary relationships, gene structures, and conservative structural domain of CAMTA3/SR1 in different plants were analyzed. Meanwhile, in the promoter region, the cis-acting elements, protein clustering interaction, and tissue-specific expression of CAMTA3/SR1 in tomato were identified. The results show that SlCAMTA3/SR1 genes possess numerous cis-acting elements related to hormones, light response, and stress in the promoter regions. SlCAMTA3 might act together with other Ca2+ signaling components to regulate Ca2+-related biological processes. Then, the expression pattern of SlCAMTA3/SR1 was also investigated by quantitative real-time PCR (qRT-PCR) analysis. The results show that SlCAMTA3/SR1 might respond positively to various abiotic stresses, especially Cd stress. The expression of SlCAMTA3/SR1 was scarcely detected in tomato leaf at the seedling and flowering stages, whereas SlCAMTA3/SR1 was highly expressed in the root at the seedling stage. In addition, SlCAMTA3/SR1 had the highest expression levels in flowers at the reproductive stage. Here, we provide a basic reference for further studies about the functions of CAMTA3/SR1 proteins in plants.
Ethylene (ETH), as a key plant hormone, plays critical roles in various processes of plant growth and development. ETH has been reported to induce adventitious rooting. Moreover, our previous studies have shown that exogenous ETH may induce plant adventitious root development in cucumber (Cucumis sativus L.). However, the key genes involved in this process are still unclear. To explore the key genes in ETH-induced adventitious root development, we employed a transcriptome technique and revealed 1415 differentially expressed genes (DEGs), with 687 DEGs up-regulated and 728 DEGs down-regulated. Using Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, we further identified critical pathways that were involved in ETH-induced adventitious root development, including carbon metabolism (starch and sucrose metabolism, glycolysis/gluconeogenesis, citrate cycle (TCA cycle), oxidative phosphorylation, fatty acid biosynthesis, and fatty acid degradation), secondary metabolism (phenylalanine metabolism and flavonoid biosynthesis) and plant hormone signal transduction. In carbon metabolism, ETH reduced the content of sucrose, glucose, starch, the activity of sucrose synthase (SS), sucrose–phosphate synthase (SPS) and hexokinase (HK), and the expressions of CsHK2, pyruvate kinase 2 (CsPK2), and CsCYP86A1, whereas it enhanced the expressions of β-amylase 1 (CsBAM1) and β-amylase 3 (CsBAM3). In secondary metabolism, the transcript levels of phenylalanine ammonia-lyase (CsPAL) and flavonoid 3′-monooxygenase (CsF3′M) were negatively regulated, and that of primary-amine oxidase (CsPAO) was positively regulated by ETH. Additionally, the indole-3-acetic acid (IAA) content and the expressions of auxin and ETH signaling transduction-related genes (auxin transporter-like protein 5 (CsLAX5), CsGH3.17, CsSUAR50, and CsERS) were suppressed, whereas the abscisic acid (ABA) content and the expressions of ABA and BR signaling transduction-related genes (CsPYL1, CsPYL5, CsPYL8, BRI1-associated kinase 1 (CsBAK1), and CsXTH3) were promoted by ETH. Furthermore, the mRNA levels of these genes were confirmed by real-time PCR (RT-qPCR). These results indicate that genes related to carbon metabolism, secondary metabolite biosynthesis, and plant hormone signaling transduction are involved in ETH-induced adventitious root development. This work identified the key pathways and genes in ETH-induced adventitious rooting in cucumber, which may provide new insights into ETH-induced adventitious root development and will be useful for investigating the molecular roles of key genes in this process in further studies.
Abscisic acid (ABA) affects many important plant processes, such as seed germination, root elongation and stomatal movement. However, little information is available about the relationship between ABA and sugar synthesis during adventitious root formation. The aim of this study was to evaluate the effect of ABA on adventitious root formation in cucumber and whether the effect of this plant hormone on sugar synthesis could be included as a causative factor for adventitious root development. We determined the contents of glucose, sucrose, starch, total sugar and sugar-related enzymes, including sucrose synthase (SS), sucrose phosphate synthase (SPS), hexokinase (HK) and pyruvate kinase (PK) activities in ABA treatment. We also quantified the relative expression of sucrose or glucose synthesis genes during this process. Increasing ABA concentrations significantly improved adventitious root formation, with the most considerable effect at 0.05 μM. Compared to the control, ABA treatment showed higher glucose, sucrose, starch and total sugar contents. Moreover, ABA treatment increased glucose-6-phosphate (G6P), fructose-6-phosphate (F6P) and glucose-1-phosphate (G1P) contents in cucumber explants during adventitious root development, which was followed by an increase of activities of sucrose-related enzymes SS and SPS, glucose-related enzymes HK and PK. ABA, meanwhile, upregulated the expression levels of sucrose or glucose synthesis-related genes, including CsSuSy1, CsSuSy6, CsHK1 and CsHK3. These results suggest that ABA may promote adventitious root development by increasing the contents of glucose, sucrose, starch, total sugar, G6P, F6P and G1P, the activities of SS, SPS, HK, SPS and the expression levels of CsSuSy1, CsSuSy6, CsHK1 and CsHK3 genes. These findings provide evidence for the physiological role of ABA during adventitious root formation and provide a new understanding of the possible relationship between ABA and sugar synthesis during adventitious rooting in plants.
The impacts of global warming on the grassland carbon cycle are increasingly severe. To explore the spatiotemporal variation in grassland soil organic carbon (SOC) and its response to climate change in Gansu Province, in this study, we designed five future-climate-scenario simulations (2019–2048), based on the baseline (1989–2018), according to the IPCC Fifth Assessment Report. The CENTURY biogeochemistry model was used to estimate the SOC of Gansu Province. One-way ANOVA and an error analysis were used to verify the model. Meanwhile, a Pearson coefficient diagram was used to analyze the main influencing factors of SOC. The results revealed that there was a good agreement between the observed and predicted SOC. The quarterly and inter-annual SOC trends of the five future-climate-scenario simulations were similar to those of the baseline simulation. The most extensive SOC storage occurred in the central Gannan region, in the simulation B scenario (temperature increase of 2 °C, no change in precipitation, and double the CO2 concentration). Temperature had a significant negative effect on SOC. Precipitation had a weak impact on SOC. The results indicate that SOC was more sensitive to temperature than to precipitation.
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