Aerial Tissues Research Articles

Allelopathic Effects of Foliar Epichloë Endophytes on Belowground Arbuscular Mycorrhizal Fungi: A Meta-Analysis

Many grasses are simultaneously symbiotic with Epichloë fungal endophytes and arbuscular mycorrhizal fungi (AMF). Epichloë endophytes are a group of filamentous fungi that colonize and grow within aerial plant tissues, such as leaves and stems. Infection and hyphal growth of Epichloë endophytes confer fitness advantages to the host plants. In addition to producing fungal alkaloids and altering host metabolic/genetic profiles, it is proven that symbiosis of plants with root/foliar endophytes affects the plant–soil relationship. We propose that the Epichloë presence/infection results in variations of soil and root AMF through allelopathic effects. We performed a meta-analysis that integrated the allelopathic effects of Epichloë endophytes on grass–AMF development. In the pre-symbiotic phase of grass–AMF symbiosis, root exudation from Epichloë-infected plants positively affected AMF growth, whereas the shoot exudates of Epichloë-infected plants inhibited AMF growth. In the symbiotic phase of grass–AMF symbiosis, the Epichloë infection was found to reduce root mycorrhizal colonization in plants. No pattern in the response of soil AMF to Epichloë presence was found. This study should improve our understanding of the impact of Epichloë endophytes on belowground microbial symbionts within the same host plant. Grass–Epichloë–AMF symbiosis may become an important model for studying above–belowground interactions.

Single-nuclei transcriptome analysis of the shoot apex vascular system differentiation in Populus.

Differentiation of stem cells in the plant apex gives rise to aerial tissues and organs. Presently, we lack a lineage map of the shoot apex cells in woody perennials - a crucial gap considering their role in determining primary and secondary growth. Here, we used single-nuclei RNA-sequencing to determine cell type-specific transcriptomes of the Populus vegetative shoot apex. We identified highly heterogeneous cell populations clustered into seven broad groups represented by 18 transcriptionally distinct cell clusters. Next, we established the developmental trajectories of the epidermis, leaf mesophyll and vascular tissue. Motivated by the high similarities between Populus and Arabidopsis cell population in the vegetative apex, we applied a pipeline for interspecific single-cell gene expression data integration. We contrasted the developmental trajectories of primary phloem and xylem formation in both species, establishing the first comparison of vascular development between a model annual herbaceous and a woody perennial plant species. Our results offer a valuable resource for investigating the principles underlying cell division and differentiation conserved between herbaceous and perennial species while also allowing us to examine species-specific differences at single-cell resolution.

TaPYL4, an ABA receptor gene of wheat, positively regulates plant drought adaptation through modulating the osmotic stress-associated processes

BackgroundAbscisic acid receptors (ABR) involve transduction of the ABA signaling in plants, impacting largely on stress-defensive physiological processes and plant osmotic stress response. In this study, we characterized TaPYL4, a gene of ABR family in T. aestivum, in mediating plant drought tolerance given scarcity of functional characterization on wheat ABR members thus far.ResultsTaPYL4 harbors nine conserved domains shared by its PYL counterparts, targeting onto plasma membrane and nucleus after endoplasmic reticulum assortment. TaPYL4 interacts with TaPP2C2 whereas the latter with TaSnRK2.1, which establish a core module of the ABA signaling pathway. TaPYL4 expression was upregulated in root and aerial tissues upon drought stress. Overexpressing TaPYL4 conferred plants improved growth traits whereas knockdown expression of target gene alleviated growth feature compared with wild type under drought treatment. The TaPYL4-enhanced drought adaptation associates gene function in positively regulating stomata movement, osmolyte biosynthesis, and root system architecture (RSA) establishment. Expression analysis on the P5CS family genes involving proline biosynthesis indicated that TaP5CS1 exerts critical roles in promoting osmolytes accumulation in drought-challenged TaPYL4 lines. TaPIN9, a PIN-FORMED gene modulating cellular auxin translocation, was validated to function as a crucial mediator in defining RSA establishment underlying TaPYL4 regulation. Transcriptome analysis revealed that TaPYL4 controls transcription of numerous genes, which impact on physiological processes associated with ‘biological process’, ‘molecular component’, and ‘cellular process’. Moreover, the differentially expressed genes mediated by TaPYL4 were closely related to stress defensive pathways.ConclusionsOur investigation suggested that TaPYL4 acts as a positive regulator in plant drought tolerance and a valuable target for engineering drought-tolerant cultivars in T. aestivum.

RNA-Seq analysis reveals the important co-expressed genes associated with polyphyllin biosynthesis during the developmental stages of Paris polyphylla

BackgroundPlants synthesize metabolites to adapt to a continuously changing environment. Metabolite biosynthesis often occurs in response to the tissue-specific combinatorial developmental cues that are transcriptionally regulated. Polyphyllins are the major bioactive components in Paris species that demonstrate hemostatic, anti-inflammatory and antitumor effects and have considerable market demands. However, the mechanisms underlying polyphyllin biosynthesis and regulation during plant development have not been fully elucidated.ResultsTissue samples of P. polyphylla var. yunnanensis during the four dominant developmental stages were collected and investigated using high-performance liquid chromatography and RNA sequencing. Polyphyllin concentrations in the different tissues were found to be highly dynamic across developmental stages. Specifically, decreasing trends in polyphyllin concentration were observed in the aerial vegetative tissues, whereas an increasing trend was observed in the rhizomes. Consistent with the aforementioned polyphyllin concentration trends, different patterns of spatiotemporal gene expression in the vegetative tissues were found to be closely related with polyphyllin biosynthesis. Additionally, molecular dissection of the pathway components revealed 137 candidate genes involved in the upstream pathway of polyphyllin backbone biosynthesis. Furthermore, gene co-expression network analysis revealed 74 transcription factor genes and one transporter gene associated with polyphyllin biosynthesis and allocation.ConclusionsOur findings outline the framework for understanding the biosynthesis and accumulation of polyphyllins during plant development and contribute to future research in elucidating the molecular mechanism underlying polyphyllin regulation and accumulation in P. polyphylla.

Exploring native Scutellaria species provides insight into differential accumulation of flavones with medicinal properties

Scutellaria baicalensis is a well-studied medicinal plant belonging to the Lamiaceae family, prized for the unique 4′-deoxyflavones produced in its roots. In this study, three native species to the Americas, S. lateriflora, S. arenicola, and S. integrifolia were identified by DNA barcoding, and phylogenetic relationships were established with other economically important Lamiaceae members. Furthermore, flavone profiles of native species were explored. 4′-deoxyflavones including baicalein, baicalin, wogonin, wogonoside, chrysin and 4′-hydroxyflavones, scutellarein, scutellarin, and apigenin, were quantified from leaves, stems, and roots. Qualitative, and quantitative differences were identified in their flavone profiles along with characteristic tissue-specific accumulation. 4′-deoxyflavones accumulated in relatively high concentrations in root tissues compared to aerial tissues in all species except S. lateriflora. Baicalin, the most abundant 4′-deoxyflavone detected, was localized in the roots of S. baicalensis and leaves of S. lateriflora, indicating differential accumulation patterns between the species. S. arenicola and S. integrifolia are phylogenetically closely related with similar flavone profiles and distribution patterns. Additionally, the S. arenicola leaf flavone profile was dominated by two major unknown peaks, identified using LC–MS/MS to most likely be luteolin-7-O-glucuronide and 5,7,2′-trihydroxy-6-methoxyflavone 7-O-glucuronide. Collectively, results presented in this study suggest an evolutionary divergence of flavonoid metabolic pathway in the Scutellaria genus of Lamiaceae.

Involvement of NGATHA-Like 1 Transcription Factor in Boron Transport under Low and High Boron Conditions.

NGATHA-Like 1 (NGAL1) transcription factor has been identified as a gene regulated through AUG-stop-mediated boron (B)-dependent translation stall; however, its function in B response remains unknown. Here, we show that NGAL1 plays an important role in the maintenance of B transport under both low- and high-B conditions in Arabidopsis thaliana. NGAL1 mRNA is accumulated predominantly in shoots in response to B stress. Independent ngal1 mutants carrying transferred DNA (T-DNA) and Ds-transposon insertions exhibit reduced B concentrations in aerial tissues and produce shortened and reduced number of siliques when B supply is limited. Furthermore, the expression of B transporter genes including nodulin 26-like intrinsic protein 6; 1 (NIP6;1), NIP5;1, NIP7;1 and borate exporter 1 (BOR1) is significantly decreased in ngal1 mutants under low-B condition, suggesting that NGAL1 is required for the transcript accumulation of B transporter genes to facilitate B transport and distribution under B limitation. Under high-B condition, ngal1 mutants exhibit reduced growth and increased B concentration in their shoots. The accumulation of BOR4 mRNA, a B transporter required for B efflux to soil, is significantly reduced in roots of ngal1 plants under high-B condition, suggesting that NGAL1 is involved in the upregulation of BOR4 in response to excess B. Together, our results indicate that NGAL1 is involved in the transcriptional regulation of B transporter genes to facilitate B transport and distribution under both low- and high-B conditions.

Perspective of Melatonin-Mediated Stress Resilience and Cu Remediation Efficiency of Brassica juncea in Cu-Contaminated Soils.

The present study evaluated the influence of melatonin (MEL) on copper toxicity in terms of morphophysiological, microscopic, histochemical, and stress resilience responses in Brassica juncea. Different levels of Cu (0, 30, and 60 mg kg–1) were given in air-dried soil, and 25 days after sowing (DAS), plants were sprayed with 30, 40, or 50 μM of MEL. The results demonstrated that under Cu stress, a significant amount of Cu accumulated in plant tissues, particularly in roots than in upper ground tissues, thereby suppressing the overall growth as evidenced by decrease in tolerance index and photosynthesis and increase in oxidative stress biomarkers (reactive oxygen species, malondialdehyde, and electrolyte leakage content) and cell death. Interestingly, the follow-up treatment of MEL, mainly 40 μM, efficiently improved the physio-biochemical and growth parameters, sugar accumulation, and metabolism. The potential of MEL in modulating Cu stress is attributed to its involvement in enriching the level of nutrient and improving chloroplast and stomatal organization besides lowering oxidative stress via enhanced levels of antioxidants. MEL improved the Cu reclamation potential in plants by enhancing Cu uptake and its translocation to aerial tissues. Principal component analysis showed that most of the morphophysiological and growth attributes were positively linked with MEL and negatively related to Cu levels, whereas all the stress-enhancing attributes showed a strong relationship with excessive Cu levels in soils. The present study suggested that MEL has the potential to improve growth and photosynthesis resulting in improved stress resilience under Cu stress along with increased remediation capability of mustard for remediation of Cu-contaminated soils.

PcNRAMP1 Enhances Cadmium Uptake and Accumulation in Populus × canescens.

Poplars are proposed for the phytoremediation of heavy metal (HM) polluted soil. Characterization of genes involved in HM uptake and accumulation in poplars is crucial for improving the phytoremediation efficiency. Here, Natural Resistance-Associated Macrophage Protein 1 (NRAMP1) encoding a transporter involved in cadmium (Cd) uptake and transport was functionally characterized in Populus × canescens. Eight putative PcNRAMPs were identified in the poplar genome and most of them were primarily expressed in the roots. The expression of PcNRAMP1 was induced in Cd-exposed roots and it encoded a plasma membrane-localized protein. PcNRAMP1 showed transport activity for Cd2+ when expressed in yeast. The PcNRAMP1-overexpressed poplars enhanced net Cd2+ influxes by 39–52% in the roots and Cd accumulation by 25–29% in aerial parts compared to the wildtype (WT). However, Cd-induced biomass decreases were similar between the transgenics and WT. Further analysis displayed that the two amino acid residues of PcNRAMP1, i.e., M236 and P405, play pivotal roles in regulating its transport activity for Cd2+. These results suggest that PcNRAMP1 is a plasma membrane-localized transporter involved in Cd uptake and transporting Cd from the roots to aerial tissues, and that the conserved residues in PcNRAMP1 are essential for its Cd transport activity in poplars.

ABSORCIÓN DIFERENCIADA DE CADMIO Y SU EFECTO EN LA FISIOLOGÍA DE SEIS GENOTIPOS DE CACAO (Theobroma cacao L.) EN SAN RAMÓN, SELVA CENTRAL DEL PERÚ

<p><strong>Background.</strong> Cacao is an important source of income, especially for small farmers in developing countries. However, its commercialization, and consequently its production, is threatened by the high levels of cadmium (Cd<sup>+2</sup>) in grains. <strong>Objective. </strong>This work was carried out with the objective of determining the differentiated uptake of six cacao genotypes in San Ramón, central Peruvian jungle. <strong>Methodology.</strong> The treatments consisted of the combination of different doses Cd<sup>+2</sup> (0, 50, 100 and 150 ppm) with the genotypes CCN-51, ICS-60, ICS-95, POUND-7 and VRAE-99. <strong>Results.</strong> The results indicate that POUND 7 absorbed a greater amount of Cd<sup>+2</sup> concentrated mainly in the root, while CCN-51 concentrated it mainly in the aerial tissues. In VRAE-99, a significant drop in stem height and diameter was observed, especially at the 150 ppm dose. This genotype was shown to be more sensitive to this metal at high doses (150 ppm) and decreased its photosynthetic rate and its efficiency in the use of water, which was confirmed by the increase in the internal carbon content. <strong>Implications.</strong> In general, it was found that POUND-7 is a promising genotype that can potentially be used as a rootstock because it is capable of accumulating Cd+2 mainly in the roots. <strong>Conclusion.</strong> Although cacao is considered a Cd<sup>+2</sup> accumulator plant, this heavy metal can negatively affect the physiology of the plant as in the case of VRAE-99. Further studies are suggested to better understand how Cd<sup>+2</sup> affects cacao physiology.</p>

A Case of Plant Vaccination: Enhancement of Plant Immunity against Verticillium dahliae by Necrotized Spores of the Pathogen.

The soil-borne fungus Verticillium dahliae is causing a devastating vascular disease in more than 200 species of dicotyledonous plants. The pathogen attacks susceptible plants through the roots, colonizes the plant vascular system, and causes the death of aerial tissues. In this study, we used Arabidopsis and eggplants to examine the plant protective and immunization effects of autoclaved V. dahliae spores against V. dahliae. We observed that the application of V. dahliae autoclaved spores in eggplants and Arabidopsis resulted in enhanced protection against V. dahliae, since the disease severity and pathogen colonization were lower in the plants treated with V. dahliae autoclaved spores when compared to controls. In addition, upregulation of the defense related genes PR1 and PDF1.2 in the Arabidopsis plants treated with the V. dahliae autoclaved spores was revealed. Furthermore, pathogenicity experiments in the Arabidopsis mutant cerk1, defective in chitin perception, revealed a loss of protection against V. dahliae in the cerk1 treated with the V. dahliae autoclaved spores. The participation of the chitin receptor CERK1 is evident in Arabidopsis immunization against V. dahliae using autoclaved spores of the pathogen.

Genome-wide identification, phylogeny and expression analysis of the SPL gene family and its important role in salt stress in Medicago sativa L.

BackgroundSQUAMOSA promoter-binding protein-like (SPL) transcription factors are widely present in plants and are involved in signal transduction, the stress response and development. The SPL gene family has been characterized in several model species, such as A. thaliana and G. max. However, there is no in-depth analysis of the SPL gene family in forage, especially alfalfa (Medicago sativa L.), one of the most important forage crops worldwide.ResultIn total, 76 putative MsSPL genes were identified in the alfalfa genome with an uneven distribution. Based on their identity and gene structure, these MsSPLs were divided into eight phylogenetic groups. Seventy-three MsSPL gene pairs arose from segmental duplication events, and the MsSPLs on the four subgenomes of individual chromosomes displayed high collinearity with the corresponding M. truncatula genome. The prediction of the cis-elements in the promoter regions of the MsSPLs detected two copies of ABA (abscisic acid)-responsive elements (ABREs) on average, implying their potential involvement in alfalfa adaptation to adverse environments. The transcriptome sequencing of MsSPLs in roots and leaves revealed that 54 MsSPLs were expressed in both tissues. Upon salt treatment, three MsSPLs (MsSPL17, MsSPL23 and MsSPL36) were significantly regulated, and the transcription level of MsSPL36 in leaves was repressed to 46.6% of the control level.ConclusionIn this study, based on sequence homology, we identified 76 SPL genes in the alfalfa. The SPLs with high identity shared similar gene structures and motifs. In total, 71.1% (54 of 76) of the MsSPLs were expressed in both roots and leaves, and the majority (74.1%) preferred underground tissues to aerial tissues. MsSPL36 in leaves was significantly repressed under salt stress. These findings provide comprehensive information regarding the SPB-box gene family for improve alfalfa tolerance to high salinity.

Effects of arbuscular mycorrhizal fungi on accumulation and translocation of selenium in winter wheat.

Selenium (Se) is an essential micronutrient for humans and animals, but not for plants. Generally, cereals including wheat and rice are the main source of dietary Se for humans. Although arbuscular mycorrhizal fungi (AMF) are ubiquitous soil microbes and commonly develop symbionts with winter wheat (Triticum aestivum L.), the influence of AMF on accumulation and translocation of Se during developmental cycle of winter wheat is still unclear. Based on a pot trial, the present results indicated that the effects of AMF on grain Se concentration in winter wheat depend on the Se species spiked in the soil and that Rhizophagus intraradices (Ri) significantly enhanced grain Se concentration under selenite treatment. Moreover, inoculation of AMF significantly increased grain Se content under selenite and selenate treatments. The enhanced grain Se content of mycorrhizal wheat could be attributed to (i) apparently increased root growth of mycorrhizal wheat at jointing could absorb more Se for translocating to aerial tissues and consequently result in significantly higher stalk Se content and (ii) enhancing Se translocation from vegetative tissues to grains. The present study showed that AMF significantly (P < 0.05) increased pre-anthesis Se uptake under selenate treatment and post-anthesis Se uptake under selenite treatment. The present study indicated the feasibility of inoculation of AMF for increasing grain Se concentration under selenite treatment and enhancing the efficiency of biofortification of Se under selenate treatments. © 2022 Society of Chemical Industry.

Characterization of the Cell Wall Component through Thermogravimetric Analysis and Its Relationship with an Expansin-like Protein in Deschampsia antarctica.

Deschampsia antarctica Desv. (Poaceae) is one of the two vascular plants that have colonized the Antarctic Peninsula, which is usually exposed to extreme environmental conditions. To support these conditions, the plant carries out modifications in its morphology and metabolism, such as modifications to the cell wall. Thus, we performed a comparative study of the changes in the physiological properties of the cell-wall-associated polysaccharide contents of aerial and root tissues of the D. antarctica via thermogravimetric analysis (TGA) combined with a computational approach. The result showed that the thermal stability was lower in aerial tissues with respect to the root samples, while the DTG curve describes four maximum peaks of degradation, which occurred between 282 and 358 °C. The carbohydrate polymers present in the cell wall have been depolymerized showing mainly cellulose and hemicellulose fragments. Additionally, a differentially expressed sequence encoding for an expansin-like (DaEXLA2), which is characterized by possessing cell wall remodeling function, was found in D. antarctica. To gain deep insight into a probable mechanism of action of the expansin protein identified, a comparative model of the structure was carried out. DaEXLA2 protein model displayed two domains with an open groove in the center. Finally, using a cell wall polymer component as a ligand, the protein–ligand interaction was evaluated by molecular dynamic (MD) simulation. The MD simulations showed that DaEXLA2 could interact with cellulose and XXXGXXXG polymers. Finally, the cell wall component description provides the basis for a model for understanding the changes in the cell wall polymers in response to extreme environmental conditions.

The association between phenanthrene and nutrients uptake in lotus cultivar 'Zhongguo Hong Beijing'.

It has been well documented that polycyclic aromatic hydrocarbon (PAHs) can be taken up from the environment by the plants and translocated into the shoots. However, the mechanisms underlying this process are poorly understood. Nelumbo nucifera L. (lotus) is a highly ornamental aquatic plant known to possess strong phytoremediation capability. In the present study, the association between phenanthrene (Phe) and nutrients, including nitrogen (N) and phosphorus (P), in lotus was investigated. Over 2years, all eight lotus cultivars tested accumulated Phe to various degrees when grown in PAH-polluted sediment (0.46mg/kg Phe). Cluster analysis showed N. nucifera 'Zhongguo Hong Beijing (ZHB)' was the one with the highest Phe levels in the leaves and petals in 2years. The Phe concentrations in the tissues of 'ZHB' were 3.14mg/kg and 1.63mg/kg on average in the first and second year, respectively. Interestingly, 'ZHB' was also the cultivar with the lowest N and P levels considering 2years and tissues. Hydroponic studies further revealed a negative association between the concentrations of Phe and those of N and P in the aerial tissues under 0.5 and 1.0mg/L Phe treatments in 'ZHB'. Furthermore, the significant reductions of the roots number (72.6%), longest root length (75.8%), and petiolar height (34.6%) in 'ZHB' seedlings exposed to 1.0mg/L Phe were observed, indicating that Phe retarded the growth of lotus. These results provide a new understanding of the accumulation of Phe in plants and the association with nutrients and enrich the basis of phytoremediation to the contaminated environment.

Multi-Dimensional Molecular Regulation of Trichome Development in Arabidopsis and Cotton.

Plant trichomes are specialized epidermal cells that are widely distributed on plant aerial tissues. The initiation and progression of trichomes are controlled in a coordinated sequence of multiple molecular events. During the past decade, major breakthroughs in the molecular understanding of trichome development were achieved through the characterization of various trichomes defective mutants and trichome-associated genes, which revealed a highly complex molecular regulatory network underlying plant trichome development. This review focuses on the recent millstone in plant trichomes research obtained using genetic and molecular studies, as well as ‘omics’ analyses in model plant Arabidopsis and fiber crop cotton. In particular, we discuss the latest understanding and insights into the underlying molecular mechanisms of trichomes formation at multiple dimensions, including at the chromatin, transcriptional, post-transcriptional, and post-translational levels. We summarize that the integration of multi-dimensional trichome-associated genes will enable us to systematically understand the molecular regulation network that landscapes the development of the plant trichomes. These advances will enable us to address the unresolved questions regarding the molecular crosstalk that coordinate concurrent and ordered the changes in cotton fiber initiation and progression, together with their possible implications for genetic improvement of cotton fiber.

Determining the Mobility of some Essential Elements in Saffron (Crocus sativus L.) by the Neutron Activation Analysis

The main purpose of this investigation is to evaluate the concentrations of six essential metals (Na+, Mg2+, K+, Ca2+, Fe2+ and Zn2+) in saffron and a farm soil using the neutron activation analysis (NAA) as a nuclear spectrometry method. The stratified random sampling method was used here. The NAA results showed the well uptake of Mg2+, K+, Ca2+, Fe2+, and Zn2+ in saffron, which is lower than the toxicity range. Based on the contamination factor and geoaccumulation index, soil contamination levels were determined uncontaminated by Zn, moderately contaminated by Na+ and Fe2+, and strongly contaminated by Ca2+, K+, and Mg2+. Results of the contamination degree and pollution load index indicated moderately/strongly soil contamination and a moderate geometric mean of the contamination index. The Na+ enrichment factor (EF) showed a minimal man-made impact on sodium enrichment. Saffron cultivation has likely caused more accumulations of Mg2+, K+, Ca2+, and Fe2+, as well as a considerable deficiency of Zn2+ in the soil, based on EFs. The biological concentration factor showed a significant zinc accumulation by the corm of saffron. There was well translocation from corm to all the aerial tissues for K+. Also, sodium adsorption ratio, exchangeable sodium percentage, pH, and electrical conductivity evaluated the non-salinity level of soil in all saffron farms.

Priming of defense-related genes in Brassica oleracea var. capitata using concentrated metabolites produced by Rhizobium tropici CIAT 899.

To verify the potential of metabolites extracted from Rhizobium tropici to trigger the priming of defense responses in cruciferous plants, we analyzed the expression of defense-related genes by qRT-PCR. Brassica oleracea var. capitata, susceptible to Xanthomonas campestris pv. campestris, were grown in greenhouse conditions. At 18days after sowing, plants were inoculated with 1mL of 1% concentrated metabolites produced by R. tropici (CM-RT) in the root. In a second experiment, leaves were sprayed with 1mL of a solution containing 1% CM-RT. Aerial and root tissue were collected separately at 0 (non-treated control condition), 24, and 48h after application, submitted to RNA extraction and gene expression analysis by qRT-PCR. The results showed that, after root treatment with CM-RT, most evaluated genes were upregulated at 24h after application and downregulated at 48h after application in roots, while in leaves, genes were downregulated both at 24 and 48h after application. On the other hand, leaf treatment with CM-RT showed that most evaluated genes in leaves and roots were upregulated at 24 and 48h after application. These results indicate that the effect of CM-RT applied in roots seems restricted to the applied region and is not sustained, while the application in leaves results in a more systemic response and maintenance of the effect of CM-RT for a longer period. The results obtained in this study emphasize the biotechnological potential of using metabolites of R. tropici as an elicitor of active defense responses in plants.

Adverse Effects of Arsenic Uptake in Rice Metabolome and Lipidome Revealed by Untargeted Liquid Chromatography Coupled to Mass Spectrometry (LC-MS) and Regions of Interest Multivariate Curve Resolution

Rice crops are especially vulnerable to arsenic exposure compared to other cereal crops because flooding growing conditions facilitates its uptake. Besides, there are still many unknown questions about arsenic’s mode of action in rice. Here, we apply two untargeted approaches using liquid chromatography coupled to mass spectrometry (LC-MS) to unravel the effects on rice lipidome and metabolome in the early stages of growth. The exposure is evaluated through two different treatments, watering with arsenic-contaminated water and soil containing arsenic. The combination of regions of interest (ROI) and multivariate curve resolution (MCR) strategies in the ROIMCR data analyses workflow is proposed and complemented with other multivariate analyses such as partial least square discriminant analysis (PLS-DA) for the identification of potential markers of arsenic exposure and toxicity effects. The results of this study showed that rice metabolome (and lipidome) in root tissues seemed to be more affected by the watering and soil treatment. In contrast, aerial tissues alterations were accentuated by the arsenic dose, rather than with the watering and soil treatment itself. Up to a hundred lipids and 40 metabolites were significantly altered due to arsenic exposure. Major metabolic alterations were found in glycerophospholipids, glycerolipids, and amino acid-related pathways.

Occurrence of Z-2-oxo-4-methyl-3-pentene-1,5-dioic acid and its regioisomer 4-methylene-2-oxo-glutaric acid in tulip tissues.

Although Z-2-oxo-4-methyl-3-pentene-1,5-dioic acid (Z-OMPD) has been identified as a major dicarboxylic acid in tulip tissues, its biosynthetic pathway has not been elucidated. Herein, Z-OMPD was isolated from tulip leaves and chemically synthesized. Comparisons of these samples revealed that Z-OMPD exists as a tautomeric mixture at physiological pH. As a regioisomer of Z-OMPD, we enzymatically and chemically prepared 4-methylene-2-oxo-glutaric acid (4-MEOG) for the first time. Using these compounds as standards, the occurrence of Z-OMPD and 4-MEOG in various tissues of the tulip cultivar "Murasakizuisho" was evaluated directly and by 2,4-dinitrophenylhydrazone derivatization. Z-OMPD was found to be abundant in the aerial tissues, whereas 4-MEOG was almost absent from all tissues. Stability analyses of Z-OMPD and 4-MEOG revealed that no double bond isomerization occurred at physiological pH, suggesting that enzyme systems are responsible for Z-OMPD biosynthesis in tulip tissues.

Role of nodes in accumulation and distribution of cadmium and its relationship with nutrient distribution and photosynthesis in the growth and regrowth of Brachiaria decumbens

Nodes play an important role in the accumulation and distribution of cadmium (Cd) in graminaceous-like rice ( Oryza sativa L.), but what about grasses used for Cd phytoextraction? In this study we evaluated i) if possible Cd accumulation in the basal node compromises the growth of Brachiaria decumbens ; ii) the role of nodes in Cd and nutrient accumulation and distribution in leaves; and iii) the relationship between Cd-induced nutritional disorders and photosynthetic impairment. B. decumbens cv. Basilisk was grown for two periods in an Oxisol presenting 0.02 (control), 2.28, 5.17 and 11.23 mg kg −1 soil with bioavailable Cd. The tillering of B. decumbens was not compromised, despite the basal node presenting high Cd concentrations, although Cd did induce stem shortening, especially in the regrowth period. Nodes restricted Cd upward transportation in the initial growth period, but Cd reached the upper nodes in the regrowth period. This result did not affect nutrient distribution into the aerial tissues of the grass. However, nutritional disorders induced by Cd appeared in the lower plant parts (especially in the growth period) due to Cd absorption by the basal node. The only effect of Cd-induced impairment on photosynthesis of B. decumbens was a reduction in instantaneous and intrinsic water use efficiency in leaf III (older), which presented higher Cd concentrations than leaves I and II (newer). In addition to the Cd effect, photosynthetic activity decreased in the regrowth period, probably in response to the lower ambient temperature in this period compared to the growth period. The nodes of B. decumbens keep Cd accumulated in the lower plant parts and avoid nutritional disorders and photosynthesis impairment in the plant leaves allowing for growth and biomass yield. • Cadmium exposure induced stem shortening and root growth impairment in Brachiaria decumbens . • Cadmium concentration followed a decreasing gradient from the basal node to the top during plant growth. • Nutrients’ concentrations were more affected by Cd in the roots and older leaves than in the newest leaves and internodes. • Photosynthesis of B. decumbens was not impaired by Cd due to a low Cd translocation to leaves.