Shoot Tissues Research Articles

Making watercress (Nasturtium officinale) cropping sustainable: genomic insights into enhanced phosphorus use efficiency in an aquatic crop.

Watercress (Nasturtium officinale) is a nutrient-dense salad crop with high antioxidant capacity and glucosinolate concentration and with the potential to contribute to nutrient security as a locally grown outdoor aquatic crop in northern temperate climates. However, phosphate-based fertilizers used to support plant growth contribute to the eutrophication of aquatic habitats, often pristine chalk streams, downstream of farms, increasing pressure to minimize fertilizer use and develop a more phosphorus-use efficient (PUE) crop. Here, we grew genetically distinct watercress lines selected from a bi-parental mapping population on a commercial watercress farm either without additional phosphorus (P-) or under a commercial phosphate-based fertilizer regime (P+), to decipher effects on morphology, nutritional profile, and the transcriptome. Watercress plants sustained shoot yield in P- conditions, through enhanced root biomass, but with shorter stems and smaller leaves. Glucosinolate concentration was not affected by P- conditions, but both antioxidant capacity and the concentration of sugars and starch in shoot tissue were enhanced. We identified two watercress breeding lines, with contrasting strategies for enhanced PUE: line 60, with highly plastic root systems and increased root growth in P-, and line 102, maintaining high yield irrespective of P supply, but less plastic. RNA-seq analysis revealed a suite of genes involved in cell membrane remodeling, root development, suberization, and phosphate transport as potential future breeding targets for enhanced PUE. We identified watercress gene targets for enhanced PUE for future biotechnological and breeding approaches enabling less fertilizer inputs and reduced environmental damage from watercress cultivation.

Time series single-cell transcriptional atlases reveal cell fate differentiation driven by light in Arabidopsis seedlings

Light serves as the energy source for plants as well as a signal for growth and development during their whole life cycle. Seedling de-etiolation is the most dramatic manifestation of light-regulated plant development processes, as massive reprogramming of the plant transcriptome occurs at this time. Although several studies have reported about organ-specific development and expression induced by light, a systematic analysis of cell-type-specific differentiation and the associated transcriptional regulation is still lacking. Here we obtained single-cell transcriptional atlases for etiolated, de-etiolating and light-grown Arabidopsisthaliana seedlings. Informative cells from shoot and root tissues were grouped into 48 different cell clusters and finely annotated using multiple markers. With the determination of comprehensive developmental trajectories, we demonstrate light modulation of cell fate determination during guard cell specialization and vasculature development. Comparison of expression atlases between wild type and the pifq mutant indicates that phytochrome-interacting factors (PIFs) are involved in distinct developmental processes in endodermal and stomatal lineage cells via controlling cell-type-specific expression of target genes. These results provide information concerning the light signalling networks at the cell-type resolution, improving our understanding of how light regulates plant development at the cell-type and genome-wide levels. The obtained information could serve as a valuable resource for comprehensively investigating the molecular mechanism of cell development and differentiation in response to light.

Elucidating growth and biochemical characteristics of rice seedlings under stress from chromium VI salt and nanoparticles.

Plants are usually provoked by a variety of heavy metal (HM) stressors that have adverse effects on their growth and other biochemical characterizations. Among the HMs, chromium has been considered the most toxic for both plants and animals. The present study was conducted to compare the phytotoxic effects of increasing chromium (VI) salt and nanoparticles (NPs) concentrations on various growth indexes of rice (Oryza sativa L. var. swat 1) seedlings grown in a hydroponic system. The 7-day rice seedlings were exposed to Cr (VI) salt and NPs hydroponic suspensions which were adjusted to the concentration of 0, 50, 100, 150, 200 and 250 mg/L. Both the Cr (VI) salt and NPs with lower concentrations (up to 100mg/L) exerted minimum inhibitory effects on the growth performance of rice seedlings. However, a significant decrease in shoot and root length and their fresh and dry weight was recorded at higher doses of Cr (VI) salt (200 mg/L) and NPs (250 mg/L). The stress induced by Cr (VI) salt has drastically affected the roots, whereas, Cr (VI) NPs significantly affected the shoot tissues. Photosynthetic pigments decreased significantly in a dose-dependent manner, and the reduction was more pronounced in rice seedlings exposed to Cr (VI) NPs compared to Cr (VI) salt. Cr (VI) NPs enhanced the membrane permeability in shoots and roots as compared to that of Cr (VI) salt, which resulted in higher concentration of reactive oxygen species (ROS) and increased lipid peroxidation. The activities of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) increased significantly in shoot/root tissue following exposure to higher doses of Cr (VI) salt (200 mg/L) and NPs stress (250 mg/L), while minor changes in CAT and APX activities were observed in root and shoot tissues after exposure to higher concentration of Cr (VI) NP. Furthermore, the increasing concentrations of Cr (VI) NPs increased the length of stomatal guard cells. Conclusively, Cr (VI) salt and NPs in higher concentrations have higher potential to damage the growth and induce oxidative stress in rice plants.

A Genome-Wide Identification and Comparative Analysis of the Heavy-Metal-Associated Gene Family in Cucurbitaceae Species and Their Role in Cucurbita pepo under Arsenic Stress.

The heavy-metal-associated (HMA) proteins are a class of PB1-type ATPases related to the intracellular transport and detoxification of metals. However, due to a lack of information regarding the HMA gene family in the Cucurbitaceae family, a comprehensive genome-wide analysis of the HMA family was performed in ten Cucurbitaceae species: Citrullus amarus, Citrullus colocynthis, Citrullus lanatus, Citrullus mucosospermus, Cucumis melo, Cucumis sativus, Cucurbita maxima, Cucurbita moschata, Cucurbita pepo, and Legenaria siceraria. We identified 103 Cucurbit HMA proteins with various members, ranging from 8 (Legenaria siceraria) to 14 (Cucurbita pepo) across species. The phylogenetic and structural analysis confirmed that the Cucurbitaceae HMA protein family could be further classified into two major clades: Zn/Co/Cd/Pb and Cu/Ag. The GO-annotation-based subcellular localization analysis predicted that all HMA gene family members were localized on membranes. Moreover, the analysis of conserved motifs and gene structure (intron/exon) revealed the functional divergence between clades. The interspecies microsynteny analysis demonstrated that maximum orthologous genes were found between species of the Citrullus genera. Finally, nine candidate HMA genes were selected, and their expression analysis was carried out via qRT-PCR in root, leaf, flower, and fruit tissues of C. pepo under arsenic stress. The expression pattern of the CpeHMA genes showed a distinct pattern of expression in root and shoot tissues, with a remarkable expression of CpeHMA6 and CpeHMA3 genes from the Cu/Ag clade. Overall, this study provides insights into the functional analysis of the HMA gene family in Cucurbitaceae species and lays down the basic knowledge to explore the role and mechanism of the HMA gene family to cope with arsenic stress conditions.

Effects of Individual or Combined Deficiency of Phosphorous and Zinc on Phenotypic, Nutrient Uptake, and Molecular Responses of Finger Millet (Eleusine coracana): A Nutri-Rich Cereal Crop.

Deficiencies of either phosphorus (P) or zinc (Zn) or both are one of the major abiotic constraints influencing agricultural production. Research on the effects of individual or combined P and Zn deficiency is limited in cereals. This study reports the effects of the individual or combined deficiency of inorganic phosphate (Pi) and Zn on the phenotypic, root hair modification, nutrient uptake, and molecular responses of finger millet (Eleusine coracana), a nutri-rich cereal crop. Finger millet seedlings were grown hydroponically under control (+Pi+Zn), individual Pi deficiency (-Pi), individual Zn deficiency (-Zn), and combined Pi and Zn deficiency (-Pi-Zn) conditions for 30 days to find the phenotypic, root hair modification, nutrient uptake, and molecular responses. Compared to the individual -Zn condition, the individual -Pi condition had more of an effect in terms of biomass reduction. The combined -Pi-Zn condition increased the root hair length and density compared to the other three conditions. The individual -Zn condition increased the Pi uptake, while the individual -Pi condition favored the Zn uptake. EcZIP2 was highly upregulated in shoot tissues under the individual -Zn condition, and EcPHT1;2 was highly expressed in root tissues under the individual -Pi condition. This is the first study to report the effects of the individual or combined deficiency of Pi and Zn in finger millet and may lead to future studies to better manage P and Zn deficiency.

The fate of bacteria in urban wastewater-irrigated peach tree: a seasonal evaluation from soil to canopy

Irrigation with wastewater can be a solution to preserve and mitigate freshwater demand, in particular during drought periods. Unfortunately, wastewater, although being treated at different levels, could be a carrier of human pathogens (e.g., E. coli) and potentially contaminate crops for human consumptions.This study investigated the seasonal microbiological concentrations, on soil, shoot and fruit tissues of potted peach trees, following two irrigation treatments: freshwater (FW) and secondary urban wastewater without the final disinfection treatment (SW).E. coli was only detected in SW irrigated soil, whereas total coliforms (TC) and total bacteria counts (TBC) were similar in both treatments throughout the season. Endophytic E. coli, Salmonella spp. and TC were not detected in shoot and fruit, but a higher presence of total bacteria (TBC) was observed in SW-irrigated tree compared to FW-irrigated tree. In particular, SW shoots had a higher load compared to fruits, thus showing a potential effect of leaf transpiration, that promoted the transfer of water-borne bacteria from soil to the epigeal part (shoot). The adoption of low-quality SW (even above the microbiological limits of the European Regulation 2020/741 for wastewater re-use in agriculture), when a drip irrigation method is applied, could be a valid alternative to save fresh water without compromising fruit safety.

Meta-Topolin-induced mass shoot multiplication and biosynthesis of valuable secondary metabolites in Stevia rebaudiana Bertoni bioreactor culture

Stevia rebaudiana Bertoni possesses various medicinal and food industrial applications. This study is the first to explore the effect of the cytokinins meta-Topolin (mT; 6-(3-hydroxybenzylamino) purine), zeatin, kinetin, and BAP (6-benzylaminopurine) at concentrations of 0 (control), 5, 10, and 15 µM on shoot multiplication, as well as stevioside, rebaudioside A, phenolic acid, and flavonoid content in bioreactor cultures. The highest number of shoots (23.4 per explant) was obtained in the medium containing 5 μM of mT. However, 15 μM of mT was superior for fresh biomass production and dry biomass accumulation. Reversed-phase (RP)-HPLC analysis showed a beneficial effect of 5 μM mT on stevioside (11.43 mg/g dry weight [DW]) and rebaudioside A (10.74 mg/g DW) biosynthesis. In all conditions, the ratio of rebaudioside A/stevioside ranged from 0.75 to 1.12. The phenolic acids chlorogenic, neochlorogenic, isochlorogenic A, and rosmarinic were confirmed in the stevia extracts, as were the flavonoids isoquercetin, and quercitrin. The highest accumulations of chlorogenic and neochlorogenic acids and flavonoids were observed in shoot tissues derived from 5 µM mT, whereas 5 µM of BAP stimulated biosynthesis of chlorogenic, isochlorogenic A, and rosmarinic acids. This is the first report on the use of mT-cytokinin showing high potential in stevia cultures.

A citrate efflux transporter important for manganese distribution and phosphorus uptake in rice.

The plant citrate transporters, functional in mineral nutrient uptake and homeostasis, usually belong to the multidrug and toxic compound extrusion transporter family. We identified and functionally characterized a rice (Oryza sativa) citrate transporter, OsCT1, which differs from known plant citrate transporters and is structurally close to rice silicon transporters. Domain analysis depicted that OsCT1 carries a bacterial citrate-metal transporter domain, CitMHS. OsCT1 showed citrate efflux activity when expressed in Xenopus laevis oocytes and is localized to the cell plasma membrane. It is highly expressed in the shoot and reproductive tissues of rice, and its promoter activity was visible in cells surrounding the vasculature. The OsCT1 knockout (KO) lines showed a reduced citrate content in the shoots and the root exudates, whereas overexpression (OE) line showed higher citrate exudation from their roots. Further, the KO and OE lines showed variations in the manganese (Mn) distribution leading to changes in their agronomical traits. Under deficient conditions (Mn-sufficient conditions followed by 8 days of 0 μm MnCl2 · 4H2 O treatment), the supply of manganese towards the newer leaf was found to be obstructed in the KO line. There were no significant differences in phosphorus (P) distribution; however, P uptake was reduced in the KO and increased in OE lines at the vegetative stage. Further, experiments in Xenopus oocytes revealed that OsCT1 could efflux citrate with Mn. In this way, we provide insights into a mechanism of citrate-metal transport in plants and its role in mineral homeostasis, which remains conserved with their bacterial counterparts.

Ultra-Fast Mass Spectrometry in Plant Biochemistry: Response of Winter Wheat Proteomics to Pre-Sowing Treatment with Iron Compounds.

In recent years, ultrafast liquid chromatography/mass spectrometry methods have been extensively developed for the use in proteome profiling in biochemical studies. These methods are intended for express monitoring of cell response to biotic stimuli and elucidation of correlation of molecular changes with biological processes and phenotypical changes. New technologies, including the use of nanomaterials, are actively introduced to increase agricultural production. However, this requires complex approbation of new fertilizers and investigation of mechanisms underlying the biotic effects on the germination, growth, and development of plants. The aim of this work was to adapt the method of ultrafast chromatography/mass spectrometry for rapid quantitative profiling of molecular changes in 7-day-old wheat seedlings in response to pre-sowing seed treatment with iron compounds. The used method allows to analyze up to 200 samples per day; its practical value lies in the possibility of express proteomic diagnostics of the biotic action of new treatments, including those intended for agricultural needs. Changes in the regulation of photosynthesis, biosynthesis of chlorophyll and porphyrin- and tetrapyrrole-containing compounds, glycolysis (in shoot tissues), and polysaccharide metabolism (in root tissues) were shown after seed treatment with suspensions containing film-forming polymers (PEG 400, Na-CMC, Na2-EDTA), iron (II, III) nanoparticles, or iron (II) sulfate. Observations at the protein levels were consistent with the results of morphometry, superoxide dismutase activity assay, and microelement analysis of 3-day-old germinated seeds and shoots and roots of 7-day-old seedlings. A characteristic molecular signature involving proteins participating in the regulation of photosynthesis and glycolytic process was suggested as a potential marker of the biotic effects of seed treatment with iron compounds, which will be confirmed in further studies.

Ethylene modulates root growth and mineral nutrients levels in trifoliate orange through the auxin-signaling pathway

Roots are fundamental to plant growth, with their development being profoundly influenced by water, mineral nutrients, and notably, plant hormones. Citrus, a leading horticultural crop cultivated globally, holds immense economic value. This study tried to investigate the roles and mechanisms effect of foliar spray 1.0 μmol/L ethephon (ETH) of ethylene and 5.0 μmol/L AgNO3 (an ethylene inhibitor) its inhibitor with auxin on root growth and mineral nutrients content levels in trifoliate orange under sand culture conditions for 45 days. Our findings indicate that ethephon treatment significantly boosted the number of lateral roots, root fresh weight, and enhanced the mineral nutrient content (N, P, K, B, Ca, Mg, Fe, Mn, and Zn, with the exception of Cu) in both root and shoot tissues. In contrast, the inhibitors notably reduced the length of lateral roots and decreased the content of P, and Fe in both root and shoot, whilst elevating Zn contents. Furthermore, ETH incited the up-regulation of auxin biosynthesis and transportation genes, leading to an increased endogenous auxin content in the lateral root-hair region. whereas, the inhibitors produced an opposite effect. We thus conclude that ethylene modulates auxin transportation and biosynthesis. This activity stimulates the auxin signaling pathway locally-specifically, in the root hair zone in the lateral root, which in turn, regulates root growth and mineral nutrient content.

Relative uptake of organic and inorganic nitrogen by common weed species

AbstractThe extent to which weed species vary in their ability to acquire and use different forms of nitrogen (N) (inorganic and organic) has not been investigated but could have important implications for weed survival and weed–crop competition in agroecosystems. We conducted a controlled environment experiment using stable isotopes to determine the uptake and partitioning of organic and inorganic N (amino acids, ammonium, and nitrate) by seven common weed and non-weed species. All species took up inorganic and organic N, including as intact amino acids. Concentrations of 15N derived from both ammonium and amino acids in shoot tissues were higher in large crabgrass [Digitaria sanguinalis (L.) Scop.] and barnyardgrass [Echinochloa crus-galli (L.) P. Beauv] than in common lambsquarters (Chenopodium album L.), redroot pigweed (Amaranthus retroflexus L.), and sorghum-sudangrass [Sorghum bicolor (L.) Moench × Sorghum bicolor (L.) ssp. drummondii (Nees ex Steud.) de Wet & Harlan]. In contrast, the concentration of 15N derived from nitrate was higher in wild mustard (Sinapis arvensis L.) shoots than in wild oat (Avena fatua L.) shoots. Root concentration of 15N derived from ammonium was lower in sorghum-sudangrass compared with other species, except for A. retroflexus and A. fatua, while root concentration of 15N derived from nitrate was lower in A. retroflexus compared with other species, except for C. album and S. arvensis. Discriminant analysis classified species based on their uptake and partitioning of all three labeled N forms. These results suggest that common agricultural weeds can access and use organic N and differentially take up inorganic N forms. Additional research is needed to determine whether species-specific differences in organic and inorganic N uptake influence the intensity of competition for soil N.

Differential Aluminum tolerance in Arabidopsis thaliana ecotypes is seemingly related to metabolite changes

Plants are negatively affected by aluminum (Al) in acidic soils (pH ≤ 5.0), which impairs root growth and ultimately plant yield. Organic acids are closely related to Al neutralization improving the metal tolerance with an expansive metabolic cost. Here, we investigated phenotypic, metabolic, and genetic responses of three Arabidopsis thaliana ecotypes, Columbia (Col-0), Wassilewskija (Ws) and Landsberg erecta (Ler) in response to Al. By comparing the respective control plants with Al-exposed plants, the ecotypes Col-0 and Ws displayed stronger reductions in root growth and reproductive yield than Ler. All ecotypes presented high expression of ALMT1, an Al-resistance associated gene. Further analyses revealed a large accumulation of diverse amino acids, carbohydrates and organic acids following Al stress in both shoot and root tissues of Col-0 and Ws plants, but not in Ler. Altogether, our results suggest that a higher capacity for using and translocating reduced carbon molecules seems crucial to overcoming Al stress in the Ler ecotype. In addition, lower expenses in carbon molecules might be linked to a higher capacity to deal with Al stress, supporting a tight relationship between primary metabolism and Al stress responses. Finally, novel insights on the influence of Al over plant growth and primary metabolism in both shoots and roots are described.

Knot formation and spread along the shoot stem in 13 olive cultivars inoculated with an indigenous pathobiome of 7 species of Pseudomonas including Pseudomonas savastanoi.

Olive knot is a widely spread disease among olive (Olea europaea L.) trees. Pseudomonas savastanoi pv. savastanoi is recognized as the primary causative agent of the disease however, recent evidence indicated that consortia of bacteria (pathobiome), may favor its development. Several factors are involved in the host-plant relationship and affect the intensity of the symptoms. Among these the presence of wounds, or damages to the plants' tissues may affect the intensity and propagation of the disease. It remains unknown whether or not bacteria move from an infected wound to another not infected one via shoot tissues. The present investigation focused on the susceptibility to olive knot of several cultivars after inoculating artificial wounds with selected Pseudomonas species, while spreading the disease from these to wounds on the same stem, that had not been purposefully inoculated. The pathobiome for the inoculum was prepared with 7 species of Pseudomonas (including Pseudomonas savastanoi pv. savastanoi), isolated from knot samples collected from two different, heavily infected olive orchards. The inoculation was done after the manual execution of 10 horizontal wounds on the stem of potted plants of 13 olive cultivars grown in the greenhouse. Only the lowest 5 wounds were inoculated. The inoculated wounds showed a maximum percentage of knots after 187 days. All 13 cultivars showed knots yet, the cultivar with the most severe disease level to Pseudomonas savastanoi pv. savastanoi was 'Rosciola colli Esini'. The metataxonomic analysis performed on the olive knots removed after 225 days confirmed the dominance of the inoculated species Pseudomonas savastanoi in all the assayed cultivars. The not inoculated wounds did not show the knot disease likely because the bacterium's inability to transmigrate from the inoculated wounds to the non-inoculated ones.

Shoot Culture of Ocimum sp. and Its Phytochemical Profile

The success of the in vitro culture technique is influenced by many factors, including the type of explants, culture medium and exogenous plant growth regulators (PGR). These factors greatly influence the speed and effectiveness of plant regeneration as well as the profile of the phytochemical compounds produced. Therefore, this study aims to determine the effect of the PGR combination on the growth response of in vitro node explants as well as the phytochemical profiles of Ocimum sp. Node explants obtained from 2 weeks old in vitro seedlings were cultured on MS medium with the addition of PGR, namely BAP and Kinetin (0.2 and 5 mg/l) combined with NAA (0.1 and 0.2 mg/l) and synthetic cytokinins alone namely Thidiazuron (TDZ) (1, 3, and 5 mg/l). The growth response of the explants and the potential for regeneration were observed for 8 weeks of culture. Effects of adding activated charcoal (AC) to root media were observed on growth of plantlets aged 2 weeks. Phytochemical profile of In vitro shoot was analyzed using GC-MS and LC-MS to be compared with its profile in in vitro callus tissue. The results showed that MS medium with the addition of a combination of cytokinin and auxin was able to induce shoot regeneration in node explants of Ocimum sp. in vitro. The Kinetin/NAA combination produced better shoot height growth, while the BAP/NAA combination produced a higher leaves number. Thidiazuron at all concentrations was able to induce shoots that were more likely to form rosettes. The addition of AC to the rooting medium did not have a positive effect on the response of shoot and plantlet growth. Chromatographic screening showed different profiles of secondary compounds in the callus and shoot tissues of Ocimum sp. in vitro. Callus composed of actively dividing cells do not produce some of the secondary compounds as produced by in vitro shoots. This shows the difference in the potential of cells or tissues in synthesizing secondary metabolites.

Effect of Lolium perenne population differences on shoot tissue nitrogen concentrations when grown on a peat soil

AbstractGrass nitrogen (N) concentrations of dairy grasslands are higher on peat soil than on mineral soils. This can lead to increased N losses to air and water from dairy farming systems on peat soils. Our hypothesis was that the use of low-N perennial ryegrass (Lolium perenne L.) genotypes could be a means to lower grass N concentrations, when grown on peat soils. Our objective was to determine whether perennial ryegrass populations with different shoot tissue N concentrations, recorded on a sandy soil, would show different shoot tissue N concentrations and N use efficiencies (NUE) or N uptake efficiencies (NUptE) when grown on a peat soil. First, a pot experiment lasting 62 days was carried out with nine diploid and seven tetraploid populations, followed by a field experiment with two diploid and two tetraploid populations and a control lasting 30 months. Both experiments had three N fertilization levels. In the pot experiment, populations explained 3% of the variation in shoot tissue N concentration among tetraploids, 5 and 7% of the variation in NUE among diploids and tetraploids and 12% of the variation in NUptE among diploids. In the field experiment, populations explained 44% of the variation in NUptE. A higher NUE coincided with lower shoot tissue N concentrations among tetraploid populations in the pot experiment. We conclude that there is potential to alter the shoot tissue N concentrations of perennial ryegrass grown on peat soil, via selection for shoot tissue N concentrations and NUE.

Comparative transcriptomic profiling reveals differentially expressed genes and important related metabolic pathways in shoots and roots of a Saudi wheat cultivar (Najran) under salinity stress.

High salinity of soil is a threatening constraint for agricultural output worldwide. The adverse effects of salt stress on plants can be revealed in different manners, from phenotypic to genetic changes. A comparative RNA-Sequencing analysis was done in roots and shoots of bread wheat, Najran cultivar between plants grown under unstressed control condition (0 mM NaCl) and salt treatment (200 mM NaCl). More than 135 million and 137 million pair-end reads were obtained from root and shoot samples, respectively. Of which, the mapped reads to Triticum aestivum genome IWGSC_V51 ranged from 83.9% to 85% in the root and 71.6% to 79% in the shoot. Interestingly, a comparison of transcriptomic profiling identified that total number of significantly differentially expressed genes (DEGs) examined in the roots was much higher than that found in the shoots under NaCl treatment, 5829 genes were differentially expressed in the roots whereas 3495 genes in the shoots. The salt-induced change in the transcriptome was confirmed by RT-qPCR using a set of randomly selected genes. KEGG enrichment analysis classified all DEGs in both roots and shoots into 25 enriched KEGG pathways from three main KEGG classes: Metabolism, organismal systems and genetic information processing. According to that, the most significantly regulated pathways in the root and shoot tissues were glutathione metabolism and biosynthesis of secondary metabolites such as phenylpropanoids and galactose metabolism suggesting that these pathways might participate in wheat salt tolerance. The findings highlight the importance of the control of oxidative stress via Glutathione and phenylpropanoids and the regulation of galactose metabolism in the roots and shoots for salt-tolerance in wheat. They open promising prospects for engineering salt-tolerance in this important crop via targeted improvement of the regulation of key genes in the production of these compounds.

Spatially activated conserved auxin-transcription factor regulatory module controls de novo root organogenesis in rice.

This study reveals that the process of crown root development and auxin-induced de novo root organogenesis during in vitro plantlet regeneration share a common auxin-OsWOX10 regulatory module in rice. In the fibrous-type root system of rice, the crown roots (CR) are developed naturally from the shoot tissues. Generation of robust auxin response, followed by activation of downstream cell fate determinants and signaling pathways at the onset of crown root primordia (CRP) establishment is essential for new root initiation. During rice tissue culture, embryonic calli are induced to regenerate shoots in vitro which undergo de novo root organogenesis on an exogenous auxin-supplemented medium, but the mechanism underlying spatially restricted root organogenesis remains unknown. Here, we reveal the dynamics of progressive activation of genes involved in auxin homeostasis and signaling during initiation and outgrowth of rice crown root primordia. By comparative global dataset analysis, we identify the crown root primordia-expressed genes whose expression is also regulated by auxin signaling. In-depth spatio-temporal expression pattern analysis shows that the exogenous application of auxin induces a set of key transcription factors exclusively in the spatially positioned CRP. Further, functional analysis of rice WUSCHEL-RELATED HOMEOBOX 10 (OsWOX10) during in vitro plantlet regeneration from embryogenic calli shows that it promotes de novo root organogenesis from regenerated shoots. Expression of rice OsWOX10 also induces adventitious roots (AR) in Arabidopsis, independent of homologous endogenous Arabidopsis genes. Together, our findings reveal that a common auxin-transcription factor regulatory module is involved in root organogenesis under different conditions.

Overlapping and specialized roles of tomato phytoene synthases in carotenoid and abscisic acid production.

Carotenoids are plastidial isoprenoids required for photoprotection and phytohormone production in all plants. In tomato (Solanum lycopersicum), carotenoids also provide color to flowers and ripe fruit. Phytoene synthase (PSY) catalyzes the first and main flux-controlling step of the carotenoid pathway. Three genes encoding PSY isoforms are present in tomato, PSY1 to PSY3. Mutants have shown that PSY1 is the isoform providing carotenoids for fruit pigmentation, but it is dispensable in photosynthetic tissues. No mutants are available for PSY2 or PSY3, but their expression profiles suggest a main role for PSY2 in leaves and PSY3 in roots. To further investigate isoform specialization with genetic tools, we created gene-edited lines defective in PSY1 and PSY2 in the MicroTom background. The albino phenotype of lines lacking both PSY1 and PSY2 confirmed that PSY3 does not contribute to carotenoid biosynthesis in shoot tissues. Our work further showed that carotenoid production in tomato shoots relies on both PSY1 and PSY2 but with different contributions in different tissues. PSY2 is the main isoform for carotenoid biosynthesis in leaf chloroplasts, but PSY1 is also important in response to high light. PSY2 also contributes to carotenoid production in flower petals and, to a lesser extent, fruit chromoplasts. Most interestingly, our results demonstrate that fruit growth is controlled by abscisic acid (ABA) specifically produced in the pericarp from PSY1-derived carotenoid precursors, whereas PSY2 is the main isoform associated with ABA synthesis in seeds and salt-stressed roots.

Silicate solubilizing and plant growth promoting bacteria interact with biogenic silica to impart heat stress tolerance in rice by modulating physiology and gene expression.

Heat stress caused due to increasing warming climate has become a severe threat to global food production including rice. Silicon plays a major role in improving growth and productivity of rice by aiding in alleviating heat stress in rice. Soil silicon is only sparingly available to the crops can be made available by silicate solubilizing and plant-growth-promoting bacteria that possess the capacity to solubilize insoluble silicates can increase the availability of soluble silicates in the soil. In addition, plant growth promoting bacteria are known to enhance the tolerance to abiotic stresses of plants, by affecting the biochemical and physiological characteristics of plants. The present study is intended to understand the role of beneficial bacteria viz. Rhizobium sp. IIRR N1 a silicate solublizer and Gluconacetobacter diazotrophicus, a plant growth promoting bacteria and their interaction with insoluble silicate sources on morpho-physiological and molecular attributes of rice (Oryza sativa L.) seedlings after exposure to heat stress in a controlled hydroponic system. Joint inoculation of silicates and both the bacteria increased silicon content in rice tissue, root and shoot biomass, significantly increased the antioxidant enzyme activities (viz. superoxidase dismutase, catalase and ascorbate peroxidase) compared to other treatments with sole application of either silicon or bacteria. The physiological traits (viz. chlorophyll content, relative water content) were also found to be significantly enhanced in presence of silicates and both the bacteria after exposure to heat stress conditions. Expression profiling of shoot and root tissues of rice seedlings revealed that seedlings grown in the presence of silicates and both the bacteria exhibited higher expression of heat shock proteins (HSPs viz., OsHsp90, OsHsp100 and 60 kDa chaperonin), hormone-related genes (OsIAA6) and silicon transporters (OsLsi1 and OsLsi2) as compared to seedlings treated with either silicates or with the bacteria alone. The results thus reveal the interactive effect of combined application of silicates along with bacteria Rhizobium sp. IIRR N1, G. diazotrophicus inoculation not only led to augmented silicon uptake by rice seedlings but also influenced the plant biomass and elicited higher expression of HSPs, hormone-related and silicon transporter genes leading to improved tolerance of seedling to heat stress.

Tea-based biochar-mediated changes in cation diffusion homeostasis in rice grown in heavy metal (loid) contaminated mining soil

Foreseeable future scenarios highlight the urgency of applying eco-safe avoidance methods or tolerance to heavy metal(loid) (HM) stress in agricultural production areas of contamination. The analyses show that the Ni, Mn, As, and Cr concentrations detected in the soils of the paddy fields in the Black Sea region vary between 123.60 and 263.30; 687–1271; 8.90–14.50; 162.00–340.00 mg kg−1 proving high accumulation of Ni, Mn, As, Cr in rice. Overconsumption of rice farmed extensively on these soils might also lead to human HM-related health problems. Therefore, in the current study, the approach of using tea-based biochar (BC) proven to have one of the most significant potentials as a soil amendment to reduce HM transmission to in-vitro-grown rice plants was investigated in the soil medium naturally contaminated with HMs. The tea-BC was produced from readily available local black tea waste of a conventional fermentation process and applied in the in-vitro experiments. Among the tested doses examined, 1% tea-BC showed a more positive effect on rice plant growth and development characterized by a better relative growth rate (59.7 and 84 mg g−1 d−1 for root and shoot tissues), photosynthetic pigment intactness (62.48 μg mL−1), cellular membrane integrity (93%), and relative water (96%) than the other rates (0% BC, 3%BC, 5%BC). The mRNA expression data highlights the probability of a cation diffusion facilitator (CDF) (OsMTP11) in concert with catalase isozyme (CATa) and dehydration-responsive element binding protein (DREB1a) linking the HM detoxification, oxidative defense, and dehydration pathways with the help of tea-BC. At the optimum concentration (1%BC), this approach might reduce HM accumulation levels of crops planted in HM-contaminated farmlands.