Ectopic over-expression of HaFT-1, a 14-3-3 protein from Haloxylon ammodendron, enhances acquired thermotolerance in transgenic Arabidopsis.

Haloxylon ammodendron, an important shrub utilized for afforestation in desert areas, can withstand harsh ecological conditions such as drought, high salt and extreme heat. A better understanding of the stress adaptation mechanisms of H. ammodendron is vital for ecological improvement in desert areas. In this study, the role of the H. ammodendron 14-3-3 protein HaFT-1 in thermotolerance was investigated. qRT-PCR analysis showed that heat stress (HS) priming (the first HS) enhanced the expression of HaFT-1 during the second HS and subsequent recovery phase. The subcellular localization of YFP-HaFT-1 fusion protein was mainly detected in cytoplasm. HaFT-1 overexpression increased the germination rate of transgenic Arabidopsis seeds, and the survival rate of HaFT-1 overexpression seedlings was higher than that of wild-type (WT) Arabidopsis after priming-and-triggering and non-primed control treatments. Cell death staining showed that HaFT-1 overexpression lines exhibited significantly reduced cell death during HS compared to WT. Transcriptome analysis showed that genes associated with energy generation, protein metabolism, proline metabolism, autophagy, chlorophyll metabolism and reactive oxygen species (ROS) scavenging were important to the thermotolerance of HS-primed HaFT-1 transgenic plants. Growth physiology analysis indicated that priming-and-triggering treatment of Arabidopsis seedlings overexpressing HaFT-1 increased proline content and strengthened ROS scavenging activity. These results demonstrated that overexpression of HaFT-1 increased not only HS priming but also tolerance to the second HS of transgenic Arabidopsis, suggesting that HaFT-1 is a positive regulator in acquired thermotolerance.

Metabolomic Analysis of the Response of Haloxylon ammodendron and Haloxylon persicum to Drought.

Haloxylon ammodendron and Haloxylon persicum, as typical desert plants in arid areas, show strong drought tolerance and environmental adaptability and are therefore ideal model plants for studying the molecular mechanisms of drought tolerance. A metabolomic analysis of H. ammodendron and H. persicum in their natural environment is lacking, and their metabolic response to drought therefore remains unclear. To elucidate the response of H. ammodendron and H. persicum to drought at the metabolic level, a non-targeted metabolomics analysis was carried out herein. Under a dry environment, H. ammodendron exhibited 296 and 252 differentially expressed metabolites (DEMs) in the positive and negative ion modes, respectively, whereas 452 and 354 DEMs were identified in the positive and negative ion modes in H. persicum, respectively. The results indicated that H. ammodendron responds to drought by increasing the content of organic nitrogen compounds and lignans, neolignans, and related compounds, and reducing the content of alkaloids and derivatives. By contrast, H. persicum adapts to the dry environment by increasing the content of organic acids and their derivatives and reducing the content of lignans, neolignans, and related compounds. In addition, H. ammodendron and H. persicum improved their osmoregulation ability, reactive oxygen species detoxification ability, and cell membrane stability by regulating the key metabolic pathways and anabolism of associated metabolites. This is the first metabolomics report on the response of H. ammodendron and H. persicum to drought in their natural environment, providing a foundation for the further study of their regulatory mechanisms under drought stress.

Combined Metabolome and Transcriptome Analysis Highlights the Host's Influence on Cistanche deserticola Metabolite Accumulation.

The medicinal plant Cistanche deserticola Ma (Orobanchaceae) is a holoparasitic angiosperm that takes life-essential materials from Haloxylon ammodendron (C. A. Mey.) Bunge (Amaranthaceae) roots. Although many experiments have been conducted to improve the quality of C. deserticola, little attention has been paid to the host's influence on metabolite accumulation. In this study, transcriptomic and metabolomic analyses were performed to unveil the host's role in C. deserticola's metabolite accumulation, especially of phenylethanoid glycosides (PhGs). The results indicate that parasitism by C. deserticola causes significant changes in H. ammodendron roots in relation to metabolites and genes linked to phenylalanine metabolism, tryptophan metabolism and phenylpropanoid biosynthesis pathways, which provide precursors for PhGs. Correlation analysis of genes and metabolites further confirms that C. deserticola's parasitism affects PhG biosynthesis in H. ammodendron roots. Then we found specific upregulation of glycosyltransferases in haustoria which connect the parasites and hosts. It was shown that C. deserticola absorbs PhG precursors from the host and that glycosylation takes place in the haustorium. We mainly discuss how the host resists C. deserticola parasitism and how this medicinal parasite exploits its unfavorable position and takes advantage of host-derived metabolites. Our study highlights that the status of the host plant affects not only the production but also the quality of Cistanches Herba, which provides a practical direction for medicinal plant cultivation.

Soil calcium prompts organic carbon accumulation after decadal saline-water irrigation in the Taklamakan desert.

Soil organic carbon (SOC), as a crucial measure of soil quality, is typically low in arid regions due to salinization, which is a global issue. How soil organic carbon changes with salinization is not a simple concept, as high salinity simultaneously affects plant inputs and microbial decomposition, which exert opposite effects on SOC accumulation. Meanwhile, salinization could affect SOC by altering soil Ca2+ (a salt component), which stabilizes organic matter via cation bridging, but this process is often overlooked. Here, we aimed to explore i) how soil organic carbon changes with salinization induced by saline-water irrigation and ii) which process drives soil organic carbon content with salinization, plant inputs, microbial decomposition, or soil Ca2+ level. To this end, we assessed SOC content, plant inputs represented by aboveground biomass, microbial decomposition revealed by extracellular enzyme activity, and soil Ca2+ along a salinity gradient (0.60-31.09 g kg-1) in the Taklamakan Desert. We found that, in contrast to our prediction, SOC in the topsoil (0-20 cm) increased with soil salinity, but it did not change with the aboveground biomass of the dominant species (Haloxylon ammodendron) or the activity of three carbon-cycling relevant enzymes (ß-glucosidase, cellulosidase, and N-acetyl-beta-glucosaminidase) along the salinity gradient. Instead, SOC changed positively with soil exchangeable Ca2+, which increased linearly with salinity. These results suggest that soil organic carbon accumulation could be driven by increases in soil exchangeable Ca2+ under salinization in salt-adapted ecosystems. Our study provides empirical evidence for the beneficial impact of soil Ca2+ on organic carbon accumulation in the field under salinization, which is apparent and should not be disregarded. In addition, the management of soil carbon sequestration in salt-affected areas should be taken into account by adjusting the soil exchangeable Ca2+ level.

Ectopic expression of NAC transcription factor HaNAC3 from Haloxylon ammodendron increased abiotic stress resistance in tobacco.

MAIN CONCLUSION: HaNAC3 is a transcriptional activator located in the nucleus that may be involved in the response to high temperature, high salt and drought stresses as well as phytohormone IAA and ABA treatments. Our study demonstrated that HaNAC3 increased the tolerance of transgenic tobacco to abiotic stress and was involved in the regulation of a range of downstream genes and metabolic pathways. This also indicates the potential application of HaNAC3 as a plant tolerance gene. NAC transcription factors play a key role in plant growth and development and plant responses to biotic and abiotic stresses. However, the biological functions of NAC transcription factors in the desert plant Haloxylon ammodendron are still poorly understood. In this study, the NAC transcription factor HaNAC3 was isolated and cloned from a typical desert plant H. ammodendron, and its possible biological functions were investigated. Bioinformatics analysis showed that HaNAC3 has the unique N-terminal NAC structural domain of NAC transcription factor. Quantitative real-time fluorescence analysis showed that HaNAC3 was able to participate in the response to simulated drought, high temperature, high salt, and phytohormone IAA and ABA treatments, and was very sensitive to simulated high temperature and phytohormone ABA treatments. Subcellular localization analysis showed that the GFP-HaNAC3 fusion protein was localized in the nucleus of tobacco epidermal cells. The transcriptional self-activation assay showed that HaNAC3 had transcriptional self-activation activity, and the truncation assay confirmed that the transcriptional activation activity was located at the C-terminus. HaNAC3 gene was expressed exogenously in wild-type Nicotiana benthamiana, and the physiological function of HaNAC3 was verified by simulating drought and other abiotic stresses. The results indicated that transgenic tobacco had better resistance to abiotic stresses than wild-type B. fuminata. Further transcriptome analysis showed that HaNAC3 was involved in the regulation of a range of downstream resistance genes, wax biosynthesis and other metabolic pathways. These results suggest that HaNAC3 may have a stress resistance role in H. ammodendron and has potential applications in plant molecular breeding.

Biology, parasitoid complex and potential distribution of saxaul's dominant defoliators, Teia dubia (Lepidoptera: Lymantriidae).

Natural enemies that impact pest populations must be understood in order to build integrated pest control strategies and to understand the most important aspects affecting pest dynamics. Haloxylon ammodendron (C. A. Mey.) Bunge is an important perennial plant species extensively used in sand stabilization and wind prevention in arid areas. This study aimed to determine the main defoliators that damage H. ammodendron and the parasitoid complex associated with them. Twelve species of defoliators were found in Northern Xinjiang, and Teia dubia (Tauscher) (Lepidoptera: Lymantriidae), Scrobipalpa sp. (Lepidoptera: Gelechiidae), and Eucharia festiva Hüfnagel (Lepidoptera: Arctiidae) were the dominant pests. T. dubia is the predominant defoliator with three generations a year. Northwest China, Central Asia, and the Mediterranean region are potentially suitable habitats for T. dubia in the world, while Xinjiang is the primary distribution area in China. Parasitoids belonging to seven species and four families were reared from the larvae of T. dubia, they were all endoparasitoids and koinobiont. Cotesia sp. (Hymenoptera: Braconidae) is the dominant parasitoid and prefer to parasitic in the 3rd-5th instar larvae. The present study provides the basis for understanding the species composition and natural enemies of lepidopteran defoliators. It will be an effective tool for the integrated pest management programs of H. ammodendron forest.

Biofertilizers with beneficial rhizobacteria improved plant growth and yield in chili (Capsicum annuum L.).

Chemical fertilizers can supply essential nutrients to crops increasing their yield, however, they can also cause serious environmental problems. Biofertilizer has received more and more attention because of its environmentally friendly and pollution-free characteristics. Haloxylon ammodendron, a desert succulent shrub, has become an important plant species for vegetation restoration in several deserts in China because of its strong drought tolerance. Its extensive root systems and unique rhizosphere bacterial community aid H. ammodendron adapt to this extreme environment. In this study, Bacillus sp. WM13-24 and Pseudomonas sp. M30-35 isolated from the rhizosphere of H. ammodendron in our previous study and Bacillus amyloliquefaciens GB03 and Sinorhizobium meliloti ACCC17578 as well-studied beneficial strains were used to prepare two types of biofertilizer, WM13-24 biofertilizer containing Bacillus sp. WM13-24 and integrated biofertilizer containing all the four strains. Results presented here showed that WM13-24 biofertilizer and the integrated biofertilizer improved chili plant growth, fruit yield and quality and the rhizosphere soil nitrogen content, enzyme activities, and the quantity and biodiversity of viable bacteria. Compared to the control, WM13-24 biofertilizer and a commercial biofertilizer, the integrated biofertilizer performed best in significantly increasing plant height, stem diameter, leaf length and width, chlorophyll content, fruit yield, soluble sugar content, ascorbic acid content, organic acid content, soil urease activity, catalase activity and the quantity and biodiversity of viable bacteria. This study provided a theoretical and practical basis for large scale development of integrated biofertilizers using beneficial rhizobacterial strains from the desert plant rhizosphere.

Sphingobacterium haloxyli sp. nov., an endophytic bacterium isolated from Haloxylon ammodendron stems in Kumtag desert.

A Gram-stain-negative, non-motile, aerobic, non-spore-forming, rod-shaped, bacterial strain, designated 5JN-11T, was isolated from Haloxylonammodendron stems in Kumtag desert, Xinjiang province, China. Strain 5JN-11T grew at salinities of 0-6 % (w/v; optimum 0-2 %), a pH of 7.0-9.0 (pH 7.0-8.0) and temperatures of 20-42 °C (28-30 °C). Based on 16S rRNA gene sequences, the strain was designated a member of the genus Sphingobacterium and the phylogenetic analysis showed that strain 5JN-11T shared the highest similarity to Sphingobacterium gobiense H7T, followed by Sphingobacterium chuzhouense DH-5T and Sphingobacterium arenae H-12T. The unfinished draft genome of strain 5JN-11T was 4.69 Mb. The G+C content of strain 5JN-11T was 42.8 mol%. The average nucleotide identity to S. gobiense H7T was 90.5 %. The respiratory quinone was MK-7, and the major polar lipids were phosphatidylethanolamine and phosphoglycolipid. The predominant cellular fatty acids were summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), iso-C15 : 0 and iso-C17 : 0 3-OH. On the basis of phenotypic, genotypic and phylogenetic evidence, strain 5JN-11T represents a novel species in the genus Sphingobacterium, for which the name Sphingobacteriumhaloxyli sp. nov. is proposed. The type strain is 5JN-11T (=ACCC 60072T=KCTC 62457T).

Induced Salt Tolerance of Perennial Ryegrass by a Novel Bacterium Strain from the Rhizosphere of a Desert Shrub Haloxylon ammodendron.

Drought and soil salinity reduce agricultural output worldwide. Plant-growth-promoting rhizobacteria (PGPR) can enhance plant growth and augment plant tolerance to biotic and abiotic stresses. Haloxylon ammodendron, a C4 perennial succulent xerohalophyte shrub with excellent drought and salt tolerance, is naturally distributed in the desert area of northwest China. In our previous work, a bacterium strain numbered as M30-35 was isolated from the rhizosphere of H. ammodendron in Tengger desert, Gansu province, northwest China. In current work, the effects of M30-35 inoculation on salt tolerance of perennial ryegrass were evaluated and its genome was sequenced to identify genes associated with plant growth promotion. Results showed that M30-35 significantly enhanced growth and salt tolerance of perennial ryegrass by increasing shoot fresh and dry weights, chlorophyll content, root volume, root activity, leaf catalase activity, soluble sugar and proline contents that contributed to reduced osmotic potential, tissue K⁺ content and K⁺/Na⁺ ratio, while decreasing malondialdehyde (MDA) content and relative electric conductivity (REC), especially under higher salinity. The genome of M30-35 contains 4421 protein encoding genes, 12 rRNA, 63 tRNA-encoding genes and four rRNA operons. M30-35 was initially classified as a new species in Pseudomonas and named as Pseudomonas sp. M30-35. Thirty-four genes showing homology to genes associated with PGPR traits and abiotic stress tolerance were identified in Pseudomonas sp. M30-35 genome, including 12 related to insoluble phosphorus solubilization, four to auxin biosynthesis, four to other process of growth promotion, seven to oxidative stress alleviation, four to salt and drought tolerance and three to cold and heat tolerance. Further study is needed to clarify the correlation between these genes from M30-35 and the salt stress alleviation of inoculated plants under salt stress. Overall, our research indicated that desert shrubs appear rich in PGPRs that can help important crops tolerate abiotic stress.

Combing both simulated and field-measured data to develop robust hyperspectral indices for tracing canopy transpiration in drought-tolerant plant.

Transpiration plays a key role in water and energy fluxes at various scales. While in recent remote sensing offers a fast and convenient method for tracing transpiration at multiple scales, the approach is mostly indirect and relies on energy balance. Although several hyperspectral indices have been reported to show potentials for tracing transpiration directly, both at leaf and canopy scales, they remain in pioneer stages and need extensive validations. In this study, we used the Soil, Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model calibrated to arid ecosystems in Central Asia, to generate a simulated dataset for validation. Furthermore, new and robust indices have been developed by combining both simulated and in situ measured datasets. Results suggested that the SR(1525, 2150), ND(1425, 2145), and previously reported index of dSR(660,1040) have significant relationships with both simulated and in situ measured transpiration. Further analyses revealed that the ND(1425,2145) shows consistent performance, even with different methodologies of combining simulation and field-measured datasets. Statistically significant results were obtained in this study, even for a dominant drought-tolerant species in arid land, a place that typically has weak vegetation reflectance under strong background radiation. We foresee the approach being conducted in other regions where vegetation reflectance dominates. This may lead to robust hyperspectral indices being developed for directly tracing transpiration at various scales.