- Polarized transport across root epithelia. [Review]
- COCurr Opin Plant Biol 2019 Jul 16; 52:23-29
- Plant roots explore the soil to acquire water and nutrients which are often available at concentrations that drastically differ from the plant's actual need for growth and development. This stark dif…
Plant roots explore the soil to acquire water and nutrients which are often available at concentrations that drastically differ from the plant's actual need for growth and development. This stark difference between availability and requirement can be dealt with owing to the root's architecture as an inverted gut. In roots, the two epithelial characteristics (selective acquisition and diffusion barrier) are split between two cell layers: the epidermis at the root periphery and the endodermis as the innermost cortical cell layer around the vasculature. Polarized transport of nutrients across the root epithelium can be achieved through different pathways: apoplastic, symplastic, or coupled transcellular. This review highlights different features of the root that allow this polarized transport. Special emphasis is placed on the coupled transcellular pathway, facilitated by polarized nutrient carriers along root cell layers but barred by suberin lamellae in endodermal cells.
- Proteome and metabolome analyses reveal differential responses in tomato -Verticillium dahliae-interactions. [Journal Article]
- JPJ Proteomics 2019 Jul 16; :103449
- Verticillium dahliae colonizes vascular tissue and causes vascular discoloration in susceptible hosts. Two well-defined races exist in V. dahliae populations from tomato and lettuce. In this study, p…
Verticillium dahliae colonizes vascular tissue and causes vascular discoloration in susceptible hosts. Two well-defined races exist in V. dahliae populations from tomato and lettuce. In this study, proteins and metabolites obtained from stems of race 1-incompatible (Beefsteak) and -compatible (Early Pak) tomato cultivars were characterized. A total of 814 and 584 proteins in Beefsteak; and 456 and 637 proteins in Early Pak were identified in stem extracts of plants inoculated with races 1 and 2, respectively. A significant number of defense-related proteins were expressed in each tomato-V. dahliae interaction, as anticipated. However, phenylalanine ammonia-lyase (PAL), an important defense-associated enzyme of the phenylpropanoid pathway, in addition to remorin 1, NAD-dependent epimerase/dehydratase, and polyphenol oxidase were uniquely expressed in the incompatible interaction. Compared with the uninoculated control, significant overexpression of gene ontology terms associated with lignin biosynthesis, phenylpropanoid pathway and carbohydrate methylation were identified exclusively in the incompatible interaction. Phenolic compounds known to be involved in plant defense mechanisms were at higher levels in the incompatible relative to the compatible interactions. Based on our findings, PAL and enzymes involved defense-related secondary metabolism and the strengthening of cell walls is likely critical to confer resistance to race 1 of V. dahliae in tomato. SIGNIFICANCE: Verticillium dahliae, a soilborne fungal pathogen and a widely distributed fungal pathogen, colonizes vascular tissue and causes vascular discoloration in roots and stems, leaf wilting, and death of susceptible plant hosts. It causes billions of dollars in annual crop losses all over the world. The study focused on the proteomic and metabalomic of V. dahliae interactions (incompatible with Beefsteak and compatible with Early Pak tomato cultivars). Based on our findings, PAL and enzymes involved defense-related secondary metabolism and the strengthening of cell walls is likely critical to confer resistance to race 1 of V. dahliae in tomato.
- Cang-ai volatile oil improves depressive-like behaviors and regulates DA and 5-HT metabolism in the brains of CUMS-induced rats. [Journal Article]
- JEJ Ethnopharmacol 2019 Jul 16; :112088
- CONCLUSIONS: CAVO can improve depressive-like behaviors concomitant with the regulation of DA and 5-HT metabolism in the brains of CUMS-induced rats.
- Sources of Inoculum and Survival of Macrophomina phaseolina in Florida Strawberry Fields. [Journal Article]
- PDPlant Dis 2019 Jul 19; :PDIS03190510RE
- Macrophomina phaseolina, the causal agent of charcoal rot, affects strawberry crowns, inducing plant collapse. The fungus survives in the soil through the production of microsclerotia and is usually …
Macrophomina phaseolina, the causal agent of charcoal rot, affects strawberry crowns, inducing plant collapse. The fungus survives in the soil through the production of microsclerotia and is usually controlled by preplant fumigation of soil. However, in the 2016 to 2017 Florida strawberry season, even after soil fumigation, about 30% plant mortality still occurred in plastic-covered beds that were used for a second season and where crop residue (mainly old strawberry crowns) was disposed of between beds. Therefore, this study was conducted to determine if M. phaseolina can survive on strawberry debris over summer in Florida and if so, verify whether strawberry debris might act as a source of inoculum for new transplants. Crowns from the previous season were collected from commercial farms where charcoal rot had been reported, and M. phaseolina was recovered from all samples. In a research field, infected crowns were buried in the soil at different depths and retrieved every 2 weeks during the summer. After 8 weeks, M. phaseolina could be recovered at all depths. Moreover, inoculation of strawberry plants by drenching the soil, dipping roots, or spraying leaves with a M. phaseolina microsclerotial suspension from pure cultures or infected crowns produced symptoms with differences in incubation periods depending on cultivar susceptibility. Furthermore, infected crowns disposed of in the aisles between beds or buried next to new transplants of cultivars Strawberry Festival, Florida Beauty, and Winterstar induced charcoal rot, with the level of aggressiveness depending on the cultivar susceptibility and inoculum placement in the field.
- Assessing the Degeneration of Cassava Under High-Virus Inoculum Conditions in Coastal Tanzania. [Journal Article]
- PDPlant Dis 2019 Jul 19; :PDIS05180750RE
- Cassava brown streak disease (CBSD), caused by cassava brown streak ipomoviruses (CBSIs), has become the most debilitating biotic stress to cassava production in East and Central Africa. Lack of CBSD…
Cassava brown streak disease (CBSD), caused by cassava brown streak ipomoviruses (CBSIs), has become the most debilitating biotic stress to cassava production in East and Central Africa. Lack of CBSD-resistant varieties has necessitated the search for alternative control measures. Most smallholder farmers reuse stems from previous crops for planting in the new season. Recycling planting material in this way can lead to "degeneration" owing to the compounding effects of disease. In this study, degeneration was defined as the increase in CBSD incidence and reduction in marketable root yield over time. An experiment was established to study the rates of degeneration in selected cassava varieties Chereko, KBH2002_135, Kipusa, Kizimbani, and Mkuranga1 and cultivars Kiroba and Kikombe under high-CBSD inoculum conditions in Bagamoyo, Tanzania from 2013 to 2017. The experiment was replicated across two seasons: the first planted during the long rains (Masika) between March and June and the second planted during the short rains (Vuli) between October and December. Mean abundance of the whitefly vector (Bemisia tabaci) was much greater during the Vuli season (>19 insects per plant) than the Masika season (<2 insects per plant). CBSD shoot symptoms occurred naturally and were observed only on Kikombe, Kiroba, and Kipusa. New materials had overall lower CBSD shoot incidences (1.5%) compared with recycled materials (6.9%) in Masika, although no significant differences were obvious in Vuli. However, Masika (8.7%) had an overall lower CBSD shoot incidence than Vuli (16.5%) in the varieties that had shoot symptoms. CBSD root incidences were higher in Vuli (10.3%) than Masika (4.4%), and root yields in Masika (29.4 t/ha) were significantly greater than those in Vuli (22.5 t/ha). The highest percentage of roots rendered unusable owing to CBSD was observed in Vuli. There was significantly higher unusable root incidence in recycled materials (3.7%) than in new materials (1.4%) in Masika but not in Vuli. Overall root yield was similar between recycled and new materials in either season. Significant reductions in root yield over the course of the experiment were observed both in Masika and Vuli, whereas changes in marketable yield were significant only in Masika. Differences in the response of varieties to degeneration led to the identification of four degeneration patterns, namely "strong," "moderate," "mild," and "delayed" degeneration. The strongest effects of degeneration were most obvious in the susceptible cultivar (Kikombe), which also had the lowest marketable yield in either season. Seasonal differences were a key driver of degeneration, because its effects were much greater in Vuli than Masika. To the best of our knowledge, this work reports the first study of degeneration caused by cassava viruses. Copyright © 2019 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
- Root endodermal barrier system contributes to defence against plant-parasitic cyst and root-knot nematodes. [Journal Article]
- PJPlant J 2019 Jul 19
- Plant-parasitic nematodes (PPNs) cause tremendous yield losses worldwide in almost all economically important crops. The agriculturally most important PPNs belong to a small group of root-infecting s…
Plant-parasitic nematodes (PPNs) cause tremendous yield losses worldwide in almost all economically important crops. The agriculturally most important PPNs belong to a small group of root-infecting sedentary endoparasites that includes cyst and root-knot nematodes. Both cyst and root-knot nematodes induce specialized long-term feeding structures in root vasculature from which they obtain their nutrients. A specialized cell layer in roots called the endodermis, which has cell walls reinforced with suberin deposits and a lignin-based Casparian strip (CS), protects the vascular cylinder against abiotic and biotic threats. Until now, the role of the endodermis, and especially of suberin and the CS, during plant-nematode interactions was largely unknown. Here, we analyzed the role of suberin and CS during interaction between Arabidopsis plants and two sedentary root parasitic nematode species, the cyst nematode Heterodera schachtii and the root-knot nematode Meloidogyne incognita. We found that nematode infection damages endodermis leading to the activation of suberin biosynthesis genes at nematode infection sites. Although feeding sites induced by both cyst and root-knot nematodes are surrounded by endodermis during early stages of infection, the endodermis is degraded during later stages of feeding site development indicating periderm formation or ectopic suberization of adjacent tissue. Chemical suberin analysis showed a characteristic suberin composition resembling peridermal suberin in nematode-infected tissue. Notably, infection assays using Arabidopsis lines with CS defects and impaired compensatory suberization, revealed that the CS and suberization impact nematode infectivity and feeding site size. Taken together, our work establishes the role of the endodermal barrier system in defense against a soil-borne pathogen. This article is protected by copyright. All rights reserved.
- Efficiency and mechanism of formaldehyde removal from air by two wild plants; Plantago asiatica L. and Taraxacum mongolicum Hand.-Mazz. [Journal Article]
- JEJ Environ Health Sci Eng 2019; 17(1):141-150
- Indoor potted plants played an important role in the removal of air-borne VOCs. According to the difference between plant fresh extracts and boiled extracts on breakdown ability to the added formalde…
Indoor potted plants played an important role in the removal of air-borne VOCs. According to the difference between plant fresh extracts and boiled extracts on breakdown ability to the added formaldehyde, a simple quantitative evaluation method was used to identify the mechanisms of formaldehyde removal from the air by wild Taraxacum mongolicum Hand.-Mazz. and Plantago asiatica L.. After shoots exposure to formaldehyde (1.28 mg/m3 in the air) for 24 h, the formaldehyde removal rates of P. asiatica and T. mongolicum were 73.18 and 121.20 mg/h/kg FW (fresh weight), respectively. Formaldehyde can be transported from the air to the rhizosphere solution by plants, and the maximum rates of transmission by T. mongolicum and P. asiatica were 23.73 and 83.08 mg/h/kg FW, respectively. Although plant metabolism was responsible for formaldehyde loss in the air-plant-solution system, and the metabolic activity depended on the enzymatic and redox reactions in the plants, P. asiatica and T. mongolicum are still good candidate species for developing phyto-microbial technologies. The redox reaction was the main mechanism used by P. asiatica shoots to dissipate formaldehyde, while the enzymatic reaction was the main mechanism used by T. mongolicum. The higher oxidative potential and lower defensive enzyme activity in P. asiatica shoots led to its higher formaldehyde removal rate compared to T. mongolicum. Meanwhile, the stronger redox reaction ability in the T. mongolicum roots was partly responsible for its lower formaldehyde transmission rate. The results show two plants have strong tolerance to formaldehyde in the air and good formaldehyde removal ability.
- Characterization and Expression Analysis of Heme Oxygenase Genes from Sorghum bicolor. [Journal Article]
- BBBioinform Biol Insights 2019; 13:1177932219860813
- Heme oxygenases (HOs) have a major role in phytochrome chromophore biosynthesis, and chromophores in turn have anti-oxidant properties. Plant heme oxygenases are divided into the HO1 sub-family compr…
Heme oxygenases (HOs) have a major role in phytochrome chromophore biosynthesis, and chromophores in turn have anti-oxidant properties. Plant heme oxygenases are divided into the HO1 sub-family comprising HO1, HO3, and HO4, and the HO2 sub-family, which consists of 1 member, HO2. This study identified and characterized 4 heme oxygenase members from Sorghum bicolor. Multiple sequence alignments showed that the heme oxygenase signature motif (QAFICHFYNI/V) is conserved across all SbHO proteins and that they share above 90% sequence identity with other cereals. Quantitative real-time polymerase chain reaction revealed that SbHO genes were expressed in leaves, stems, and roots, but most importantly their transcript level was induced by osmotic stress, indicating that they might play a role in stress responses. These findings will strengthen our understanding of the role of heme oxygenases in plant stress responses and may contribute to the development of stress tolerant crops.
- A new glance on root-to-shoot in vivo zinc transport and time-dependent physiological effects of ZnSO4 and ZnO nanoparticles on plants. [Journal Article]
- SRSci Rep 2019 Jul 18; 9(1):10416
- Understanding nanoparticle root uptake and root-to-shoot transport might contribute to the use of nanotechnology in plant nutrition. This study performed time resolved experiments to probe Zn uptake,…
Understanding nanoparticle root uptake and root-to-shoot transport might contribute to the use of nanotechnology in plant nutrition. This study performed time resolved experiments to probe Zn uptake, biotransformation and physiological effects on Phaseolus vulgaris (L.). Plants roots were exposed to ZnO nanoparticles (40 and 300 nm) dispersions and ZnSO4(aq) (100 and 1000 mg Zn L-1) for 48 h. Near edge X-ray absorption spectroscopy showed that 40 nm ZnO was more easily dissolved by roots than 300 nm ZnO. It also showed that in the leaves Zn was found as a mixture Zn3(PO4)2 and Zn-histidine complex. X-ray fluorescence spectroscopy showed that root-to-shoot Zn-translocation presented a decreasing gradient of concentration and velocity, it seems radial Zn movement occurs simultaneously to the axial xylem transport. Below 100 mg Zn L-1, the lower stem tissue section served as a buffer preventing Zn from reaching the leaves. Conversely, it was not observed for 1000 mg Zn L-1 ZnSO4(aq). Transcriptional analysis of genes encoding metal carriers indicated higher expression levels of tonoplast-localized transporters, suggesting that the mechanism trend to accumulate Zn in the lower tissues may be associated with an enhanced of Zn compartmentalization in vacuoles. The photosynthetic rate, transpiration, and water conductance were impaired by treatments.
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- The F-box Protein SAGL1 and ECERIFERUM3 Regulate Cuticular Wax Biosynthesis in Response to Changes in Humidity in Arabidopsis. [Journal Article]
- PCPlant Cell 2019 Jul 18
- Cuticular waxes that cover the above-ground parts of land plants are essential for their survival in terrestrial environment. However, little is known about the regulatory mechanisms underlying cutic…
Cuticular waxes that cover the above-ground parts of land plants are essential for their survival in terrestrial environment. However, little is known about the regulatory mechanisms underlying cuticular wax biosynthesis in response to changes in ambient humidity. Here, we report that SMALL AND GLOSSY LEAVES 1 (SAGL1) Kelch repeat F-box protein mediates proteasome-dependent degradation of ECERIFERUM3 (CER3), a biosynthetic enzyme that is involved in the production of very long chain alkanes, which are the major wax components and thereby negatively regulates cuticular wax biosynthesis in Arabidopsis. Disruption of SAGL1 caused severe growth retardation, enhanced tolerance to drought and increased wax accumulation in stems, leaves, and roots. Cytoplasmic SAGL1 physically interacts with CER3 and targets CER3 for degradation. GUS expression was observed in roots of pSAGL1::GUS plants, but barely detected in their aerial organs. High humidity-induced levels of GUS activity and SAGL1 transcripts were reduced by ABA treatment and water-deficit. SAGL1 protein levels also increased under high humidity and its stability is regulated by the 26S proteasome. This study revealed that the SAGL1-CER3 module negatively regulates Arabidopsis cuticular wax biosynthesis in response to changes to humidity conditions and suggested the importance of permeable cuticle formation in terrestrial plants under high humidity.