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[Display omitted] • Desert is one of the harshest places on the earth due to low precipitation and soil nutrients. • Global desertification is a continuous process; almost 60% of the land surface is now desertified. • The plants in these desert ecosystems have developed several novel phenotypic characteristics that overcome the harsh environment. • Genome sequencing of the desert plant can enable us to identify the novel trait responsible for overcoming the xerophytic condition. • Transfer of novel genetic traits can be done to the crop plants. So that plants can withstand the harsh environment and overcome crop loss due to drought and other extreme conditions. Despite the exposure to arid environmental conditions across the globe ultimately hampering the sustainability of the living organism, few plant species are equipped with several unique genotypic, biochemical, and physiological features to counter such harsh conditions. Physiologically, they have evolved with reduced leaf size, spines, waxy cuticles, thick leaves, succulent hydrenchyma, sclerophyll, chloroembryo, and photosynthesis in nonfoliar and other parts. At the biochemical level, they are evolved to perform efficient photosynthesis through Crassulacean acid metabolism (CAM) and C4 pathways with the formation of oxaloacetic acid (Hatch-Slack pathway) instead of the C3 pathway. Additionally, comparative genomics with existing data provides ample evidence of the xerophytic plants' positive selection to adapt to the arid environment. However, adding more high-throughput sequencing of xerophyte plant species is further required for a comparative genomic study toward trait discovery related to survival. Learning from the mechanism to survive in harsh conditions could pave the way to engineer crops for future sustainable agriculture. The distinct physiology of desert plants allows them to survive in harsh environments. However, the genomic composition also contributes significantly to this and requires great attention. This review emphasizes the physiological and genomic adaptation of desert plants. Other important parameters, such as desert biodiversity and photosynthetic strategy, are also discussed with recent progress in the field. Overall, this review discusses the different features of desert plants, which prepares them for harsh conditions intending to translate knowledge to engineer plant species for sustainable agriculture. This review comprehensively presents the physiology, molecular mechanism, and genomics of desert plants aimed towards engineering a sustainable crop. [ABSTRACT FROM AUTHOR]

As a crucial aspect of terrestrial ecosystems, water plays a key role in soil hydrological cycling and ecological management. However, limited knowledge exists on how soil water varies along rock fragment content (RFC) beneath plants. In this study, we investigated soil water content (SWC) and relative soil water deficit (DSWC) with four RFC levels ranging from 0 to 75 % (V/V) under four native species, including A. vestita , B. brachycarpa , C. szechuanensis , and S. davidii , and their relationships with soil physical properties and plant functional traits. Results showed that an increase in RFC significantly decreased SWC (except A. vestita) at soil depth of 10–50 cm and altered its vertical trend from unimodal to increasing under each plant. Notable differences in SWC between the wet and dry seasons in 75 % RFC disappeared under A. vestita and B. brachycarpa , suggesting that the RFC changed the spatiotemporal patterns of the SWC. DSWC generally decreased as soil depths deepened under A. vestita with shallow roots, in contrast to increasing under other deep-rooted species (B. brachycarpa , C. szechuanensis , and S. davidii). The seasonal variance of DSWC basically decreased with soil depth. This indicated that the plants generally deceased SWC, particularly in the wet season, and the effect depended on interspecific traits. SWC and DSWC had closely relationships with soil physical properties and plant performing. We suggest that varying RFC indirectly impacted soil water not only via altering soil structure and temperature, but also by shaping plant characteristics (especially root distribution and architecture), mediating plant effect on the spatiotemporal dynamics of SWC. [ABSTRACT FROM AUTHOR]

Agave is recognized as a low recalcitrant material, which makes it a potential source to obtain nanocellulose. Aqueous dispersions (in water, H 2 O 2 , H 2 O 2 /H 2 SO 4 ) of agave powder were heated at 120 °C under vapor pressure (1 kg/cm 2 ). The resultant materials were observed with an optical microscope (OM), a laser scanning microscope (LSM) to obtain the thickness measurement and a scanning electron microscope (SEM) to observe morphology. Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to obtain the chemical structure. Cellulose nanoplatelets (CNPs) from Agave salmiana were successfully isolated under mild conditions. Physicochemical analysis indicates that lignin was removed in a single step oxidation with hydrogen peroxide in presence of sulfuric acid at low concentration (0.17 M). The CNPs images revealed the presence of entangled cellulose nanofibrils (Ø ≈ 14 nm) along the nanoplatelets (thickness ≈80 nm). [ABSTRACT FROM AUTHOR]

Psammochloa villosa is a perennial herbaceous plant that is dominant within arid regions of the Inner Mongolian Plateau and the Qinghai-Tibet Plateau in China, where it is an endemic species and exhibits strong drought tolerance and wind resistance. To study drought tolerance in P. villosa and determine its molecular basis, we simulated high and moderate drought stress in a controlled environment and then analyzed transcriptome sequences by combining long-read sequences from a representative, wild-grown individual with short reads from the treatment groups. We obtained 184,076 high-quality isoforms as a reference and 168,650 genes (91.6%), which we were able to annotate according to public databases. Ultimately, we obtained 119,005 unigenes representing the transcriptome of P. villosa under drought stress and, among these, we identified 3089 differentially expressed genes and 1484 transcription factors. Physiologically, P. villosa that was exposed to high and moderate drought stress had reduced germination rates and shorter buds but generated more chlorophyll, which is atypical under drought stress and possibly reflects an adaptation of these plants to their arid environment. We inferred that significantly upregulated genes were annotated as 'Chlorophyll a - b binding protein' and 'Light-harvesting chlorophyll-protein' among drought and control groups. Broadly, our analyses revealed that drought stress triggered many genome-level responses, especially related to mitigation of radical oxygen species (ROS), which increase in concentration under drought stress. In particular, in the high drought stress group compared with the control, GO enrichment analysis revealed a significant enrichment of upregulated genes (n = 10) involved in mitigation of oxidative stress. Similarly, using KEGG we found significant enrichment of genes in the phenylpropanoid biosynthesis pathway (11 genes), which yields phenols that scavenge ROS. We also inferred that many genes involved in metabolism of arginine and proline, which may serve as both scavengers of ROS and osmoprotectants that interact with stress response genes based on our protein–protein interaction network analysis. We verified the relative expression levels of eight genes associated with mitigation of ROS, DNA repair, and transmembrane transporter activity using qRT-PCR, and the results were consistent with our inferences from transcriptomes. This study provides insights into the genomic and physiological basis of drought tolerance in P. villosa and represents a resource for development of the species as a forage crop via molecular breeding within arid lands. [ABSTRACT FROM AUTHOR]

Abstract: Seed coat development of Harpagophytum procumbens (Devil''s Claw) and the possible role of the mature seed coat in seed dormancy were studied by light microscopy (LM), transmission electron microscopy (TEM) and environmental scanning electron microscopy (ESEM). Very young ovules of H. procumbens have a single thick integument consisting of densely packed thin-walled parenchyma cells that are uniform in shape and size. During later developmental stages the parenchyma cells differentiate into 4 different zones. Zone 1 is the multi-layered inner epidermis of the single integument that eventually develops into a tough impenetrable covering that tightly encloses the embryo. The inner epidermis is delineated on the inside by a few layers of collapsed remnant endosperm cell wall layers and on the outside by remnant cell wall layers of zone 2, also called the middle layer. Together with the inner epidermis these remnant cell wall layers from collapsed cells may contribute towards seed coat impermeability. Zone 2 underneath the inner epidermis consists of large thin-walled parenchyma cells. Zone 3 is the sub-epidermal layers underneath the outer epidermis referred to as a hypodermis and zone 4 is the single outer seed coat epidermal layer. Both zones 3 and 4 develop unusual secondary wall thickenings. The primary cell walls of the outer epidermis and hypodermis disintegrated during the final stages of seed maturation, leaving only a scaffold of these secondary cell wall thickenings. In the mature seed coat the outer fibrillar seed coat consists of the outer epidermis and hypodermis and separates easily to reveal the dense, smooth inner epidermis of the seed coat. Outer epidermal and hypodermal wall thickenings develop over primary pit fields and arise from the deposition of secondary cell wall material in the form of alternative electron dense and electron lucent layers. ESEM studies showed that the outer epidermal and hypodermal seed coat layers are exceptionally hygroscopic. At 100% relative humidity within the ESEM chamber, drops of water readily condense on the seed surface and react in various ways with the seed coat components, resulting in the swelling and expansion of the wall thickenings. The flexible fibrous outer seed coat epidermis and hypodermis may enhance soil seed contact and retention of water, while the inner seed coat epidermis maintains structural and perhaps chemical seed dormancy due to the possible presence of inhibitors. [Copyright &y& Elsevier]

• Atriplex originated in Aralo-Caspian and the Pontic floristic region in the Oligocene. • Atriplex invaded most of the continents several times independently via long-distance dispersal. • The highest alpha diversity of Atriplex was found in Australia and the New World. • Most dispersal events took place into the Mediterranean region. Atriplex is the most species-rich genus of Amaranthaceae and one of the largest C 4 clades in eudicots. Distributed predominantly in the arid subtropical and temperate regions worldwide, many Atriplex species dominate the plant communities of harsh and inhospitable inland and coastal habitats. Current threats of aridification and salinisation increase the ecological and economic value of this highly stress tolerant xerophytic genus. We compiled sequence data of approximately 80 % (208 spp.) of all currently recognised species and carried out a phylogenetic reconstruction using nuclear-encoded internal and external transcribed spacers. In addition, time divergence estimation analysis and ancestral area reconstruction were carried out to reconstruct the worldwide spread of Atriplex. Our results show that Atriplex originated in continental Asia during the Oligocene and dispersed from there across the world, often via long-distance dispersal from the Aralo-Caspian and the Pontic regions, or the floristic province of Turkestan. The highest alpha diversity was retrieved from arid habitats of Australia and the New World resulting from extensive radiation events of the Late Miocene and Pliocene. Most dispersal events took place into the Mediterranean region. Atriplex invaded most continents several times independently from different regions throughout the continuous cooling trend of the Neogene and the Quaternary. Despite limited resolution power of the used molecular markers, this study allows for a more comprehensive understanding of the evolutionary history of Atriplex and lays the foundation for future evolutionary studies of saltbushes. [ABSTRACT FROM AUTHOR]

Abstract: The osmotic adjustment traits of Suaeda physophora (euhalophyte), Haloxylon ammodendron (xero-halophyte) and Haloxylon persicum (xerophyte) were investigated both in field and under controlled conditions. The results showed that percentage of inorganic solutes in total solutes was over 90%, while the estimated contribution of Na+ to Ψ s was over 50% for the two halophytic species, in field condition. The percentages of inorganic solutes and organic solutes were 66% and 34%, respectively, and the estimated contribution of Na+ to Ψ s was less than 18%, while the estimated contribution of soluble sugars to Ψ s was over 20% in H. persicum, in field condition. The estimated contribution of proline to Ψ s was less than 0.2% for all species both in field and under salt stress in a greenhouse experiment. The estimated contribution of NO3 − to Ψ s was less than 4% for all species in field condition. In greenhouse experiment, the concentration of NO3 − was higher under various NaCl treatments than that in control condition for S. physophora; the estimated contribution of NO3 − to Ψ s was over 7% in S. physophora, and it was higher than that in other species at various treatments. In conclusion, inorganic ions especially Na+ were more important in osmoregulation for S. physophora and H. ammodendron to adapt to saline and arid environment, while organic solutes, especially soluble sugars played more important role in drought adaptation in the xerophyte, H. persicum. Proline did not play an important role in osmoregulation for all species both in field and controlled conditions. NO3 − played more important role in osmoregulation in S. physophora and H. ammodendron cultured in full-strength Hoagland''s nutrient solution under NaCl treatments compared with that growing in saline soils in field condition. [Copyright &y& Elsevier]

• We genuinely appreciate the reviewers for the comments, concerns and suggestions. • It provides us opportunity to observe our research from reviewers' view and made us more thinking and more understanding our own work. In most terrestrial plants, large quantities of water inevitably are diffused into the air via open stomata for CO 2 absorption during photosynthesis. It is difficult to reduce such an intrinsic demand of water for transpiration but still maintain photosynthesis. Interestingly, the xerophyte Zygophyllum xanthoxylum evolves an outstanding ability to resolve this dilemma by accumulating Na+ to stimulate growth while reducing transpiration. However, the underlying mechanisms are still unclear. Two-week-old Z. xanthoxylum plants were treated with 50 mM NaCl (Na) for 7 days to investigate their growth, gas-exchange related parameters, chlorophyll fluorescence parameters, leaf anatomical characteristics, and related biochemical traits. NaCl treatment reduced the stomatal opening and transpiration but markedly enhanced the plant biomass. Analysis showed that a higher efficiency of intrinsic water use (WUE i) and photosynthetic chlorophyll (P Chl) in leaves of Na-treated plants. A lower CO 2 partial pressure in substomatal cavities, mainly accounting for higher WUE i , which efficiently facilitates CO 2 extraction from air via partially opening stomata in leaves of Na-treated plants, may be largely due to increased internal cell surface and reduced CO 2 diffusion path between chloroplasts and corresponding cell wall, in addition to increased expression of aquaporin and induced C 4 or CAM-like metabolism. Increased leaves area, reduced chlorophyll content per unit weight, and enhanced operating efficiency of Photosystem II allowed more efficient light harvesting, deeper light penetration and more light using efficiency, and so would also benefit this water-saving photosynthesis. Our data demonstrate that Z. xanthoxylum efficiently rematches both CO 2 intake and light use to fulfill vigorous growth under significantly reduced stomatal aperture and markedly decreased water consumption. The mechanisms that Z. xanthoxylum uses to achieve more biomass while using less water give a valuable clue for future improvement of agricultural production in water-limited areas. [ABSTRACT FROM AUTHOR]

• ZxNRT1.5 was mainly expressed in the root stele of Zygophyllum xanthoxylum. • ZxNRT1.5 in roots was induced by salt treatments and osmotic stress. • ZxNRT1.5 mediated root-to-shoot NO 3 − transport and enhanced NO 3 − uptake. • ZxNRT1.5 modulated salt and drought tolerance by regulating NO 3 −, Na+, K+ transport. The Nitrate Transporter1/Peptide Transporter family member NPF7.3/NRT1.5 is responsible for long-distance transport of NO 3 − and involved in affecting salt and drought tolerance in plants. However, current studies have only focused on AtNRT1.5 from the stress-sensitive glycophyte Arabidopsis. In this study, the function of the NRT1.5 homolog ZxNRT1.5 from the typical xerophyte Zygophyllum xanthoxylum in ion transport and plants' salt and drought tolerance was analyzed. The results indicated that ZxNRT1.5 was mainly expressed in the root stele, and its expression level was significantly induced by salt treatments and osmotic stress. Overexpression of ZxNRT1.5 in Arabidopsis showed that ZxNRT1.5 mediated root-to-shoot NO 3 − transport and contributed to enhancing NO 3 − uptake. Overexpression of ZxNRT1.5 increased Na+ accumulation by decreasing the expression of AtHKT1;1 in roots, and promoted root-to-shoot transport of K+ probably by changing polarization of cell membrane under salt stress. Meanwhile, ZxNRT1.5 -overexpressing lines exhibited stronger tolerance to mannitol-induced osmotic stress, resulted from an increased accumulation of NO 3 − and the accumulation of a small quantity of Na+ that was beneficial for plant growth. These findings suggest that ZxNRT1.5 is not only essential for long-distance transport and accumulation of NO 3 −, but also involved in regulating Na+ and K+ transport, thereby modulating salt and drought tolerance. [ABSTRACT FROM AUTHOR]