Arbuscular Mycorrhizal Fungal Inoculation Increases Organic Selenium Accumulation in Soybean (Glycine max (Linn.) Merr.) Growing in Selenite-Spiked Soils.

Selenium (Se) is an essential trace element for humans. Arbuscular mycorrhizal fungi (AMF) play a crucial role in increasing plant micronutrient acquisition. Soybean (Glycine max (Linn.) Merr.) is a staple food for most people around the world and a source of Se. Therefore, it is necessary to study the mechanism of Se intake in soybean under the influence of AMF. In this study, the effects of fertilization with selenite and inoculation with different AMF strains (Claroideoglomus etunicatum (Ce), Funneliformis mosseae (Fm)) on the accumulation and speciation of Se in common soybean plants were discussed. We carried out a pot experiment at the soil for 90 days to investigate the impact of fertilization with selenite and inoculation with Ce and Fm on the Se fractions in soil, soybean biomass, accumulation and speciation of Se in common soybean plants. The daily dietary intake of the Se (DDI) formula was used to estimate the risk threshold of human intake of Se from soybean seeds. The results showed that combined use of both AMF and Se fertilizer could boost total Se and organic Se amounts in soyabean seeds than that of single Se application and that it could increase the proportion of available Se in soil. Soybean inoculated with Fm and grown in soil fertilized with selenite had the highest organic Se. The results suggest that AMF inoculation could promote root growth, more soil water-soluble Se and higher Se uptake. The maximum Se intake of soybean for adults was 93.15 µg/d when treated with Se fertilizer and Fm, which satisfies the needs of Se intake recommended by the WHO. Combined use of AMF inoculation and Se fertilizer increases the bioavailable Se in soil and promotes the total Se concentration and organic Se accumulation in soybean. In conclusion, AMF inoculation combined with Se fertilization can be a promising strategy for Se biofortification in soybean.

COVID-19 Crisis: How Can Plant Biotechnology Help?

The emergence of the COVID-19 pandemic has led to significant public health crisis all over the world. The rapid spreading nature and high mortality rate of COVID-19 places a huge pressure on scientists to develop effective diagnostics and therapeutics to control the pandemic. Some scientists working on plant biotechnology together with commercial enterprises for the emergency manufacturing of diagnostics and therapeutics have aimed to fulfill the rapid demand for SARS-CoV-2 protein antigen and antibody through a rapid, scalable technology known as transient/stable expression in plants. Plant biotechnology using transient/stable expression offers a rapid solution to address this crisis through the production of low-cost diagnostics, antiviral drugs, immunotherapy, and vaccines. Transient/stable expression technology for manufacturing plant-based biopharmaceuticals is already established at commercial scale. Here, current opinions regarding how plant biotechnology can help fight against COVID-19 through the production of low-cost diagnostics and therapeutics are discussed.

A phytoremediation coupled with agro-production mode suppresses Fusarium wilt disease and alleviates cadmium phytotoxicity of cucumber (Cucumis sativus L.) in continuous cropping greenhouse soil.

Cadmium (Cd) contamination and continuous cropping obstacle often coexist in greenhouse soil and seriously restrict cucumber production. In this study, hyperaccumulator Sedum alfredii Hance was intercropped with spring cucumber (Cucumis sativus L.), then rotated with low accumulator water spinach and autumn cucumber under rational water regime, composited amendment was applied to soil before transplanting autumn cucumber. The results showed that, compared with conventional crop rotation system (Chinese cabbage and cucumber rotation), superposition management practice suppressed Fusarium wilt disease by 28.4 and 57.4% and increased yield by 35.2 and 383% for spring and autumn cucumbers, respectively. Meanwhile, photosynthetic characteristics, antioxidant system and fruit quality were significantly improved. Furthermore, this mode modified soil microbial community structure, enhanced soil enzyme activities, and simultaneously reduced soil total and phytoavailable Cd by 30.3 and 47.7%, respectively. These results demonstrated a feasible technical system to achieve phytoremediation coupled with argo-production in Cd contaminated greenhouse soil with continuous cropping obstacle and provided useful information for further revelation of interaction mechanisms between multicropping and comprehensive biofortification measurements.

Endophytic inoculation coupled with soil amendment and foliar inhibitor ensure phytoremediation and argo-production in cadmium contaminated soil under oilseed rape-rice rotation system.

Phytoremediation coupled with agro-production is a sustainable strategy for remediation of toxic metal contaminated farmlands without interrupting crop production. In this study, high accumulating oilseed rape was rotated with low accumulating rice to evaluate the effects of crop rotation on growth performance and uptake of cadmium (Cd) in plants. In this system, oilseed rape was inoculated with plant growth promoting endophyte (PGPE) consortium, and rice was applied with soil composite amendment and foliar inhibitor. The results showed, compared with rice monoculture, crop rotation coupled with superposition measure has potential to enhance yield, biomass and nutritional quality of both crops, as well as to increase Cd uptake in non-edible tissues of oilseed rape and to reduce Cd concentration in individual parts of rice, thus accelerating phytoextraction and ensuring food safety. These comprehensive management practices removed 7.03 and 7.91% total Cd from two experiment fields, respectively, in three years phytoremediation. These results demonstrated a feasible technical mode for phytoremediation coupled with argo-production in slightly Cd contaminated field, and also provided useful information for further investigation of interaction mechanisms between the rotated crops and biofortification measures.

Foliar application of zinc and selenium alleviates cadmium and lead toxicity of water spinach - Bioavailability/cytotoxicity study with human cell lines.

The present study investigated the effects of foliar application of zinc (Zn) and selenium (Se) on bioavailability of Zn and Se and toxicity of cadmium (Cd) and lead (Pb) to different water spinach ecotypes (LA and HA) grown in slightly (XZ) or moderately (LJY) contaminated fields via in vitro digestion combined with Caco-2/HL-7702 cell model. The obtained results revealed that foliar application of Zn and Se promoted yield, increased total, bioaccessible and bioavailable fractions of Zn and Se in plants, indicating that foliar application is a feasible way of biofortification. Although there was no significant effect on liver cell proliferation (MTT), membrane stability (LDH) and hepatocyte enzyme (ALT and AST) activities, the obvious ecotype and soil dependent fluctuations of lipid peroxidation (MDA) and antioxidant enzyme (SOD, POD and CAT) activities in serum highly suggest that the low accumulator and clean field should be used in agricultural production rather than the high accumulator and contaminated farmland. Moreover, foliar application of Zn and Se improved nutritional quality of all water spinach genotypes in both fields, including increased Fe, vitamin C, cellulose and chlorophyll, maintained concentrations of potassium (K), manganese (Mn), copper (Cu), protein, and nitrate. These results demonstrate that this agricultural management practice may prove to be an effective approach for minimizing health risk and alleviating "hidden hunger" in the developing countries.

Bioaccessibility and Human Exposure Assessment of Cadmium and Arsenic in Pakchoi Genotypes Grown in Co-Contaminated Soils.

In many countries cadmium (Cd) and arsenic (As) commonly coexist in soils contaminated by mining activities, and can easily enter the human body via consumption of leafy vegetables, like the popularly consumed pakchoi (Brassica chinensis L.), causing major health concerns. In the present study, bioaccessibility and human exposure of Cd and As were assessed in twenty genotypes of pakchoi cultured at two different levels of co-contamination to identify low health risk genotypes. The bioaccessibilities of Cd and As represent a fraction of the total metals content could be bioaccessible for human, in the present study, significant differences in pakchoi Cd and As bioaccessibility were observed among all tested genotypes and co-contaminated levels. Cd and As bioaccessibility of pakchoi were in the ranges of 24.0-87.6% and 20.1-82.5%, respectively, for in the high level co-contaminated soils, which was significantly higher than for low level co-contaminated soils with 7.9-71.8% for Cd bioaccessibility and 16.1-59.0% for As bioaccessibility. The values of bioaccessible established daily intakes (BEDI) and the total bioaccessible target hazard quotients (TBTHQ) of Cd and As were also considerably higher in high level co-contaminated soils than in low level co-contaminated soils. Two genotypes (Meiguanqinggengcai and Zhenqing60F1) contained relatively low concentrations and bioaccessible Cd and As and, their BEDI and TBTHQ for Cd and As ranged below the tolerable limits set by the FAO/WHO (BEDI of Cd < 0.83 µg kg-1 bw day-1, BEDI of As < 3 µg kg-1 bw day-1) and United States Environmental Protection Agency (TBTHQ for Cd and As < 1), this applied for both levels of co-contaminated soils for adults and children. Consequently, these findings suggest identification of safe genotypes in leafy vegetable with low health risk via genotypic screening and breeding methods could be a useful strategy to ensure the safety of food crops grown in those Cd and As co-contaminated fields due to mining activities.

Enhanced expression of SaHMA3 plays critical roles in Cd hyperaccumulation and hypertolerance in Cd hyperaccumulator Sedum alfredii Hance.

MAIN CONCLUSION: The enhanced expression of a P 1B -type ATPase gene ( SaHMA3 ) is essential for Cd hyperaccumulation and hypertolerance in Sedum alfredii Hance. A functional understanding of the mechanism through which hyperaccumulator plants accumulate and tolerate extremely toxic metals is a prerequisite for the development of novel strategies for improving phytoremediation using engineered plants or natural hyperaccumulators as well as biofortification and food crop safety. Most hyperaccumulator species, however, are small and slow-growing, and their potential for large-scale decontamination of polluted soils is limited. Sedum alfredii Hance, the only one metal hyperaccumulator from the Crassulaceae family, is an ideal candidate for gaining a functional understanding of the intra-family hyperaccumulation mechanisms as well as their potential applications. In the present study, we isolated and functionally characterized a P1B-type ATPase gene (SaHMA3) from S. alfredii Hance. SaHMA3 alleles from a hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) were constitutively expressed in both shoot and root and encoded tonoplast-localized proteins, but showed differences in transport substrate specificity and expression level. SaHMA3 h from the HE plant was a Cd transporter. In contrast, SaHMA3n from NHE plants was able to transport both Zn and Cd. SaHMA3 showed a significantly higher constitutive expression level in HE plants than in NHE plants. Furthermore, the expression level of SaHMA3 in the shoots of HE plants was considerably higher than in the roots. Overexpression of SaHMA3h in tobacco plants significantly enhanced Cd tolerance and accumulation and greatly increased the root sequestration of Cd. In summary, our data suggested that SaHMA3 plays critical roles in Cd hyperaccumulation and hypertolerance in Cd hyperaccumulator S. alfredii Hance.

Characterization of (68)Zn uptake, translocation, and accumulation into developing grains and young leaves of high Zn-density rice genotype.

Zinc (Zn) is an essential micronutrient for humans, but Zn deficiency has become serious as equally as iron (Fe) and vitamin A deficiencies nowadays. Selection and breeding of high Zn-density crops is a suitable, cost-effective, and sustainable way to improve human health. However, the mechanism of high Zn density in rice grain is not fully understood, especially how Zn transports from soil to grains. Hydroponics experiments were carried out to compare Zn uptake and distribution in two different Zn-density rice genotypes using stable isotope technique. At seedling stage, IR68144 showed higher (68)Zn uptake and transport rate to the shoot for the short-term, but no significant difference was observed in both genotypes for the long-term. Zn in xylem sap of IR68144 was consistently higher, and IR68144 exhibited higher Zn absorption ratio than IR64 at sufficient (2.0 µmol/L) or surplus (8.0 µmol/L) Zn supply level. IR64 and IR68144 showed similar patterns of (68)Zn accumulation in new leaves at seedling stage and in developing grains at ripening stage, whereas (68)Zn in new leaves and grains of IR68144 was consistently higher. These results suggested that a rapid root-to-shoot translocation and enhanced xylem loading capacity may be the crucial processes for high Zn density in rice grains.