Harzianopyridone Supplementation Reduced Chromium Uptake and Enhanced Activity of Antioxidant Enzymes in Vigna radiata Seedlings Exposed to Chromium Toxicity

Mycorrhizosphere bacteria inhibit greenhouse gas emissions from microplastics contaminated soil by regulating soil enzyme activities and microbial community structure

Microplastics (MPs) accumulation in terrestrial ecosystems can affect greenhouse gases (GHGs) production by altering microbial and soil structure. Presently, research on the MPs effect on plants is not consistent, and underlying molecular mechanisms associated with GHGs are yet unknown. For the first time, we conducted a microcosm study to explore the impact of MPs addition (Raw vs. aged) and Trichoderma longibrachiatum and Bacillus subtilis inoculation (Sole vs. combination) on GHGs emission, soil community structure, physiochemical properties, and enzyme activities. Our results indicated that the addition of aged MPs considerably enhanced the GHGs emissions (N2O (+16%) and CO2 (+21%), respectively), C and N cycling gene expression, microbial biomass carbon, and soil physiochemical properties than raw MPs. However, the soil microbial community structure and enzyme activities were enhanced in raw MPs added treatments, irrespective of the MPs type added to soil. However, microbial inoculation significantly reduced GHGs emission by altering the expression of C and N cycling genes in both types of MPs added treatments. The soil microbial community structure, enzymes activities, physiochemical properties and microbial biomass carbon were enhanced in the presence of microbial inoculation in both type of MPs. Among sole and combined inoculation of Trichoderma and Bacillus subtilis, the co-applied Trichoderma and Bacillus subtilis considerably reduced the GHGs emission (N2O (-64%) and CO2 (-61%), respectively) by altering the expression of C and N cycling genes regardless of MPs type used. The combined inoculation also enhanced soil enzyme activities, microbial community structure, physiochemical properties and microbial biomass carbon in both types of MPs treatment. Our findings provide evidence that polyethylene MPs likely pose a high risk of GHGs emission while combined application of Trichoderma and Bacillus subtilis significantly reduced GHGs emission by altering C and N cycling gene expression, soil microbial community structure, and enzyme activities under MPs pollution in a terrestrial ecosystem.

A Marine Natural Product, Harzianopyridone, as an Anti-ZIKV Agent by Targeting RNA-Dependent RNA Polymerase

The Zika virus (ZIKV) is a mosquito-borne virus that already poses a danger to worldwide human health. Patients infected with ZIKV generally have mild symptoms like a low-grade fever and joint pain. However, severe symptoms can also occur, such as Guillain-Barré syndrome, neuropathy, and myelitis. Pregnant women infected with ZIKV may also cause microcephaly in newborns. To date, we still lack conventional antiviral drugs to treat ZIKV infections. Marine natural products have novel structures and diverse biological activities. They have been discovered to have antibacterial, antiviral, anticancer, and other therapeutic effects. Therefore, marine products are important resources for compounds for innovative medicines. In this study, we identified a marine natural product, harzianopyridone (HAR), that could inhibit ZIKV replication with EC50 values from 0.46 to 2.63 µM while not showing obvious cytotoxicity in multiple cellular models (CC50 > 45 µM). Further, it also reduced the expression of viral proteins and protected cells from viral infection. More importantly, we found that HAR directly bound to the ZIKV RNA-dependent RNA polymerase (RdRp) and suppressed its polymerase activity. Collectively, our findings provide HAR as an option for the development of anti-ZIKV drugs.

Chromium and arsenic bioaccumulation and biomass potential of pink morning glory (Ipomoea carnea Jacq.)

Soil contamination with heavy metals and metalloids is a global concern nowadays. Phytoremediation is an eco-friendly, cost-effective, and sustainable way of mitigating such contamination by utilizing the plants' ability to accumulate, sequester, and stabilize elements. Biomass-producing plants may outperform hyperaccumulators in terms of total elemental removal and offer more cost-effectiveness through their usable biomass. Ipomoea carnea is a wild plant in the Asian region. It is resilient, spreads rapidly in a wide range of soil conditions, and has a high potential for biomass feedstock. In this work, we have tested this plant species for its growth performance and accumulation characteristics of Cr and As. In a pot experiment, the plants could easily grow from rootless stem segments in 2 weeks when garden soils are treated with 100-500 ppm of Cr and 20-300 ppm of As. Plant growth reduction was little at the moderate level of these elements, with a significant accumulation of elements in 45 days. Within this time, in the stems and leaves, the Cr concentrations were found to be 49 and 39 ppm, respectively, when treated with 500 ppm of Cr, whereas the As concentrations were obtained as 83 and 28 ppm, respectively, for the treatment with 300 ppm of As. To estimate the biomass production potential, the plant was grown with a density of 80,000 per ha under normal field conditions (without metal stress). At the harvest, the plants consisted of 80% stems, 11% leaves, and 9% belowground portions on a dry weight basis. The dry weight of stems, leaves, and belowground parts was 31.3%, 17.9%, and 23.7%, respectively. Overall, the estimated biomass was 25.8 Mg/ha/year from three harvests. The ability to regrow from the basal part makes it useful for continuous sequestration of toxic elements over multiple harvests. Our results show that I. carnea could lower Cr and As from contaminated soils and potentially a phytoremediation candidate considering accumulation rate and high amount of usable biomass production.

Optimizing Sugarcane Growth, Yield, and Quality in Different Ecological Zones and Irrigation Sources Amidst Environmental Stressors

The imbalanced use of fertilizers and irrigation water, particularly supplied from groundwater, has adversely affected crop yield and harvest quality in sugarcane (Saccharum officinarum L.). In this experiment, we evaluated the impact of potassium (K) and micronutrients [viz. Zinc (Zn), Iron (Fe), and Boron (B)] application and irrigation water from two sources, viz. canal, and tube well water on sugarcane growth, yield, and cane quality under field trails. Water samples from Mardan (canal water) and Rahim Yar Khan (tube well water) were analyzed for chemical and nutritional attributes. The results revealed that tube well water's electrical conductivity (EC) was three-fold that of canal water. Based on the EC and total dissolved salts (TDS), 83.33% of the samples were suitable for irrigation, while the sodium adsorption ratio (SAR) indicated only a 4.76% fit and a 35.71% marginal fit compared with canal water. Furthermore, the application of K along with B, Fe, and Zn had led to a significant increase in cane height (12.8%, 9.8%, and 10.6%), cane girth (15.8%, 15.6%, and 11.6%), cane yield (13.7%, 12.3%, and 11.5%), brix contents (14%, 12.2%, and 13%), polarity (15.4%, 1.4%, and 14%), and sugar recovery (7.3%, 5.9%, and 6%) in the tube well irrigation system. For the canal water system, B, Fe, and Zn increased cane height by 15.3%, 13.42%, and 11.6%, cane girth by 13.9%, 9.9%, and 6.5%, cane yield by 42.9%, 43.5%, and 42%, brix content by 10.9%, 7.7%, and 8%, polarity by 33.4%, 28%, and 30%, and sugar recovery by 4.0%, 3.9%, and 2.0%, respectively, compared with sole NPK application. In conclusion, the utilization of tube well water in combination with canal water has shown better results in terms of yield and quality compared with the sole application of canal water. In addition, the combined application of K and B significantly improved sugarcane yields compared with Zn and Fe, even with marginally suitable irrigation water.

Chromium in plant growth and development: Toxicity, tolerance and hormesis

Research over the last three decades showed that chromium, particularly the oxyanion chromate Cr(VI) behaves as a toxic environmental pollutant that strongly damages plants due to oxidative stress, disruption of nutrient uptake, photosynthesis and metabolism, and ultimately, represses growth and development. However, mild Cr(VI) concentrations promote growth, induce adventitious root formation, reinforce the root cap, and produce twin roots from single root meristems under conditions that compromise cell viability, indicating its important role as a driver for root organogenesis. In recent years, considerable advance has been made towards deciphering the molecular mechanisms for root sensing of chromate, including the identification of regulatory proteins such as SOLITARY ROOT and MEDIATOR 18 that orchestrate the multilevel dynamics of the oxyanion. Cr(VI) decreases the expression of several glutamate receptors, whereas amino acids such as glutamate, cysteine and proline confer protection to plants from hexavalent chromium stress. The crosstalk between plant hormones, including auxin, ethylene, and jasmonic acid enables tissues to balance growth and defense under Cr(VI)-induced oxidative damage, which may be useful to better adapt crops to biotic and abiotic challenges. The highly contrasting responses of plants manifested at the transcriptional and translational levels depend on the concentration of chromate in the media, and fit well with the concept of hormesis, an adaptive mechanism that primes plants for resistance to environmental challenges, toxins or pollutants. Here, we review the contrasting facets of Cr(VI) in plants including the cellular, hormonal and molecular aspects that mechanistically separate its toxic effects from biostimulant outputs.

Morpho-physiological growth performance and phytoremediation capabilities of selected xerophyte grass species toward Cr and Pb stress

Being sessile organisms, plants cannot escape unwanted changes in the environment. The rapid human population explosion caused significant environmental problems. Heavy metals produced through various sources can cause severe damage to living organisms. The study was planned to evaluate four grass species' morpho-physiological growth characteristics and phytoremediation capabilities under chromium (Cr) and lead stress (Pb) in the arid climate. Typha angustifolia, Tragus roxburghii, Aeluropus logopoides, and Cenchrus ciliaris grass species were used for the study. One-year-old stubbles from the Cholistan desert were used for the experiment. Cr treatments in the form of K₂Cr₂O₇ were applied at 0, 20, 40, and 80 mg L^-1, whereas Pb was applied as PbCl₂ at 0, 50, 200, and 500 mg L^-1 as control, low, moderate and high-stress, respectively. After 6 weeks of heavy metals treatments, plants were harvested and analyzed for growth performance and phytoremediation capabilities. Results depicted that, regarding morphological attributes, T. angustifolia performed better, followed by C. ciliaris; no clear pattern was observed for T. roxburghii and A. logopoides. The CO₂ assimilation rate (Co₂d) and water use efficiency (WUE) increased as the heavy metal stress increased in all species under both metals. In contrast, total chlorophyll content was higher under low stress. Other physiological parameters, such as relative humidity (RHd), net photosynthetic rate (A), transpiration rate (E), stomatal conductance (Gs), leaf internal CO2 concentration (Ci) and membrane stability index (MSI) gradually decreased as the Cr, and Pb stress levels increased among all the species. Moreover, Cr and Pb absorption contents of T. angustifolia were higher than the other three species at each stress level. Overall, T. angustifolia thrived against heavy metals stress and showed higher biomass, maximum photosynthetic measurements, WUE and higher metal absorption among all the selected species. Results concluded that although all the selected species behaved fine under stress conditions, T. angustifolia performance was better; thus, it can be used to remediate the soil near industrial estates.