The Uptake, Transfer, and Detoxification of Cadmium in Plants and Its Exogenous Effects.

Cadmium (Cd) exerts a toxic influence on numerous crucial growth and development processes in plants, notably affecting seed germination rate, transpiration rate, chlorophyll content, and biomass. While considerable advances in Cd uptake and detoxification of plants have been made, the mechanisms by which plants adapt to and tolerate Cd toxicity remain elusive. This review focuses on the relationship between Cd and plants and the prospects for phytoremediation of Cd pollution. We highlight the following issues: (1) the present state of Cd pollution and its associated hazards, encompassing the sources and distribution of Cd and the risks posed to human health; (2) the mechanisms underlying the uptake and transport of Cd, including the physiological processes associated with the uptake, translocation, and detoxification of Cd, as well as the pertinent gene families implicated in these processes; (3) the detrimental effects of Cd on plants and the mechanisms of detoxification, such as the activation of resistance genes, root chelation, vacuolar compartmentalization, the activation of antioxidant systems and the generation of non-enzymatic antioxidants; (4) the practical application of phytoremediation and the impact of incorporating exogenous substances on the Cd tolerance of plants.

Evolution and Expression Patterns of the Fructose 1,6-Bisphosptase Gene Family in a Miracle Tree (Neolamarckia cadamba).

Neolamarckia cadamba (N. cadamba) is a fast-growing tree species with tremendous economic and ecological value; the study of the key genes regulating photosynthesis and sugar accumulation is very important for the breeding of N. cadamba. Fructose 1,6-bisphosptase (FBP) gene has been found to play a key role in plant photosynthesis, sugar accumulation and other growth processes. However, no systemic analysis of FBPs has been reported in N. cadamba. A total of six FBP genes were identifed and cloned based on the N. cadamba genome, and these FBP genes were sorted into four groups. The characteristics of the NcFBP gene family were analyzed such as phylogenetic relationships, gene structures, conserved motifs, and expression patterns. A cis-acting element related to circadian control was first found in the promoter region of FBP gene. Phylogenetic and quantitative real-time PCR analyses showed that NcFBP5 and NcFBP6 may be chloroplast type 1 FBP and cytoplasmic FBP, respectively. FBP proteins from N. cadamba and 22 other plant species were used for phylogenetic analyses, indicating that FBP family may have expanded during the evolution of algae to mosses and differentiated cpFBPase1 proteins in mosses. This work analyzes the internal relationship between the evolution and expression of the six NcFBPs, providing a scientific basis for the evolutionary pattern of plant FBPs, and promoting the functional studies of FBP genes.

Tannin tolerance lactic acid bacteria screening and their effects on fermentation quality of stylo and soybean silages.

Some excellent legume forages are difficult to ensile naturally due to their high buffering capacity and low water-soluble carbohydrate content. This may cause serious problems like proteolysis. In the present study, strains of lactic acid bacteria with high acid productivity and high tannin tolerance were screened from different silages and combined with tannic acid (TA) as an addition to ensiling. The screened strains were identified as Lactobacillus plantarum (LP), with four of these strains then selected for their high tannin tolerance. Stylosanthes guianensis and whole-plant soybean (WPS) were ensiled with 1 and 2% (fresh matter basis) TA, four LP strains alone (6 log10 colony forming units per gram of fresh matter), or TA combined with LP strains. Fermentation parameters and in vitro rumen fermentation characteristics were analyzed after 30 days of fermentation. The results showed that TA + LP can be used to reduce pH values (P < 0.01), non-protein nitrogen (P < 0.01), and ammonia-nitrogen (P < 0.01). The in vitro crude protein digestibility of WPS silage was also decreased with the addition of TA + LP (P < 0.01). These results indicate that the addition of TA combined with tannin tolerance LP strains may improve the fermentation quality of legume silage, especially for reducing proteolysis.

The physiological and transcriptomic study of secondary growth in Neolamarckia cadamba stimulated by the ethylene precursor ACC.

Though many biological roles of ethylene have been investigated intensively, the molecular mechanism of ethylene's action in woody plants remains unclear. In this study, we investigated the effects of exogenous 1-aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene, on the growth of Neolamarckia cadamba seedlings, a fast-growing tropical tree. After 14 days of ACC treatment, the plants showed a reduced physiological morphology while stem diameter increased; however, this did not occur after the addition of 1-MCP. Meanwhile, the lignin content of N. cadamba also increased. Transcriptome analysis revealed that the expression of the ethylene biosynthesis and signaling genes ACC oxidase (ACO) and ethylene insensitive 3 (EIN3) were up-regulated mainly at the 6th hour and the 3rd day of the ACC treatment, respectively. The transcription levels of transcription factors, mainly in the basic helix-loop-helix (bHLH), ethylene response factor (ERF), WRKY and v-myb avian myeloblastosis viral oncogene homolog (MYB) families, involved in the ethylene signaling and secondary growth also increased significantly. Furthermore, in accordance to the increased lignification of the stem, the transcriptional level of key enzymes in the phenylalanine pathway were elevated after the ACC treatment. Our results revealed the physiological and molecular mechanisms underlying the secondary growth stimulated by exogenous ACC treatment on N. cadamba seedlings.

Beneficial Effects of Tannic Acid on the Quality of Bacterial Communities Present in High-Moisture Mulberry Leaf and Stylo Silage.

Tannic acid (TA), a type of polyphenol, is widely distributed in plants, especially in legumes. Not only does it possess antimicrobial properties, but it also has the ability to bind with proteins. The fermentation parameters, nitrogen fractions, antioxidant capacity, and bacterial communities present in mulberry leaves and stylo (Stylosanthes guianensis) ensiled with or without 1 and 2% TA per kilogram of fresh matter (FM) were investigated after 75 days' fermentation. The results showed that 1 and 2% TA both significantly decreased the butyric acid content (4.39 and 7.83 g/kg dry matter (DM), respectively) to an undetectable level in both mulberry leaf and stylo silage. In addition, 2% TA significantly increased the contents of lactate (24.0-39.0 and 8.50-32.3 g/kg DM), acetate (18.0-74.5 and 9.07-53.3 g/kg DM), and the antioxidant capacity of both mulberry leaf and stylo silage, respectively. With the addition of 1 and 2% TA, the pH values (5.55-5.04 and 4.87, respectively) and ammonia-N (NH3-N) content (85.5-27.5 and 16.9 g/kg total nitrogen (TN), respectively) were all significantly decreased in stylo silage. In addition, TA increased the relative abundance of Weissella, Acinetobacter, and Kosakonia spp. and decreased that of undesirable Clostridium spp. TA can thus be used to improve the silage quality of both mulberry leaf and stylo silage, with 2% TA being the better concentration of additive to use.

Solid state fermentation of Moringa oleifera leaf meal by mixed strains for the protein enrichment and the improvement of nutritional value.

Moringa oleifera Lam. (MO) is a fast-growing multi-purpose deciduous tree with high biomass and nutritional value. However, the presence of antinutritional factors, poor palatability, and indigestibility of Moringa oleifera leaf meal (MOLM) restrict its application to animal feed. This study aimed to obtain high-quality protein feeds via solid-state fermentation (SSF) of MOLM. The process conditions for increasing the true protein (TP) content using Aspergillus niger, Candida utilis and Bacillus subtilis co-cultures were optimized, and the chemical composition of MOLM was compared before and after fermentation. The results of this study showed that the highest TP content could be obtained through mixed-strain culture of A. niger, C. utilis and B. subtilis at a ratio of 1:1:2. The MOLM was inoculated with A. niger, followed by C. utilis and B. subtilis 24 h later. The optimized co-culture parameters were as follows: total inoculation size, 24%; temperature, 32 °C; fermentation time, 6.5 days; and initial water content, 60%. The maximum TP yield was 28.37%. Notably, in the fermented MOLM (FMOLM), the content of nutrients such as crude protein (CP), small peptides, and total amino acids (AAs) were significantly increased relative to unfermented MOLM, whereas the contents of crude fiber (CF), tannin, and phytic acid were significantly decreased. MOLM analysis using scanning electron microscopy (SEM) revealed that SSF disrupted the surface structure of MOLM, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that macromolecular proteins were degraded. The in vitro protein digestibility (IVPD) of FMOLM was also improved significantly. Our findings suggest that multi-strain fermentation with A. niger, C. utilis and B. subtilis improves the nutritional quality of MOLM, rendering it a viable functional feedstuff for use in livestock industries in the future.

Effects of citric acid on fermentation characteristics and bacterial diversity of Amomum villosum silage.

To study the effects of citric acid on fermentation process of Amomum villosum silage, A. villosum was ensiled without or with 1%, 2% citric acid and fermentation parameters and bacterial diversity were analyzed after 3, 7, 14, 30 days ensiling, respectively. Citric acid treated silages had lower dry matter loss (1.83% vs 2.23%), pH (3.84 vs 6.02), ammonia-N (0.33 vs 1.79 g/kg DM) and coliform bacteria number (<2.00 vs 7.27 log10 CFU/g FM) than the control after 30 days ensiling. The relative abundance of lactic acid bacteria, Pediococcus and Lactobacillus increased, whereas undesirable microorganisms like Enterobacter, Escherichia-Shigella and Pantoea decreased in citric acid treated A. villosum silage. These results indicated that quality A. villosum silage could be obtained by citric acid addition.

In vitro induction and characterisation of tetraploid drumstick tree (Moringa oleifera Lam.).

Artificial induction of polyploidy is widely used in breeding programmes to improve the agronomic traits. The drumstick tree (Moringa oleifera Lam.) has a range of potential commercial uses, as the vegetative organs have high nutritional, medicinal, and feed values. In the present study, in vitro tetraploidisation in drumstick tree was performed by treating leaf segments with colchicine and subsequently verifying the ploidy levels. For polyploidisation, explant survival and regeneration rates were affected more by exposure time than by colchicine concentration, and the highest polyploidisation efficiency was observed at 500 mg/L colchicine for 3 days, which yielded 21% tetraploids. The morphological characteristics and contents of seven fodder-related nutrients (crude protein, ether extract, ash, acid detergent fibre, neutral detergent fibre, calcium, and phosphorus) in the leaves and shoots were compared between tetraploid and diploid drumstick trees. The resulting tetraploids showed significantly enhanced leaf and stomatal size. In addition, the contents of seven fodder-related nutrients were higher, although to varying degrees, in tetraploids than in diploids. The results indicated that the tetraploid produced in this study exhibited superior agronomical traits and improved biomass yield than diploids, and may represent excellent raw materials for fodder to enhance biomass and nutrition.

Improving the quality of rice straw silage with Moringa oleifera leaves and propionic acid: Fermentation, nutrition, aerobic stability and microbial communities.

Mixed ensiling is believed an effective way to improve nutrient preservation and utilization. The effect of mixing Moringa oleifera leaves (MOL) on silage quality, aerobic stability and microbial communities of rice straw ensiled with/without propionic acid were investigated after 140 days fermentation. The results showed that mixing MOL decreased the pH (4.69 vs 3.85), butyric acid (17.4 g/kg DM vs not detected), ammonia-N (3.36 vs 2.17 g/kg DM) and fiber contents (626 vs 462 g/kg DM) but increased protein content (88.4 vs 125 g/kg DM) of rice straw silages. It also increased the relative abundance of Lactobacillus (12.96% vs 50.82%) at unsealing and Issatchenkia (2.02% vs 36.03%) after exposure to air, and might improve aerobic stability of silages. The addition of propionic acid could inhibit deaminization activity during ensiling and exposure to air. It is suggested mixing MOL could improve the fermentation quality and nutrition of rice straw silage.

Dynamics of fermentation quality, physiochemical property and enzymatic hydrolysis of high-moisture corn stover ensiled with sulfuric acid or sodium hydroxide.

A better understanding of biomass usability during storage would offer basis for management decisions in production. High-moisture corn stover was ensiled with sulfuric acid (H2SO4, 0.3% and 0.6%) or sodium hydroxide (NaOH, 0.5% and 1.0%) and ensiling characteristics, lignocellulosic profile and enzymatic saccharification were investigated on day 3, 7, 15, 30 and 60 of ensiling. The results showed that 0.6% H2SO4 reduced dry matter loss (9.81% to 6.34%) and ammonia-N content (3.89 to 1.04 g/kg DM) during ensiling, whereas it was converse for NaOH treatment (19.89%, 5.74 g/kg DM). Hemicellulose was reduced (27.98% to 22.61%, 16.81% DM) by 0.6% H2SO4 or 1.0% NaOH. Saccharification yield was decreased (306 to 229 mg/g DM) during ensiling, which was improved (229 to 356, 277 mg/g DM) by H2SO4 and NaOH treatments. This study suggests that ensiling with addition of 0.6% H2SO4 could improve nutrient preservation and saccharification yield of high-moisture corn stover.

Ensiling characteristics, proteolysis and bacterial community of high-moisture corn stalk and stylo silage prepared with Bauhinia variegate flower.

Bauhinia variegate flower (BVF) was supposed to improve silage fermentation due to its abundant active components. Thus, corn stalk and stylo were ensiled with addition of 0, 5% or 10% BVF, and then ensiling characteristics, protein fraction and bacterial community were analyzed after 60-day fermentation. The contents of butyric acid (2.9 vs not detected, 13.2 vs 3.0 g/kg DM in corn stalk and stylo silage, respectively), ammonia-N (100.2 vs 83.2, 110.8 vs 61.9 g/kg total N) and free amino acid (35.6 vs 16.5, 35.0 vs 16.4 g/kg total N) were decreased in 10% BVF treated silages. The bacterial diversity was increased, where the relative abundance of Enterobacter or Clostridium decreased and that of lactic acid producing bacteria such as Lactobacillus, Weissella or Enterococcus increased. It is suggested that BVF could be used to improve fermentation quality and nutrient preservation of high-moisture corn stalk and stylo silage.

Dynamics of proteolysis, protease activity and bacterial community of Neolamarckia cadamba leaves silage and the effects of formic acid and Lactobacillus farciminis.

To investigate the reason for well preservation of protein in Neolamarckia cadamba leaves (NCL) during ensiling, fresh NCL were ensiled with or without addition of 2.0 mL/kg formic acid (FA) or 1.0 × 109CFU/kg Lactobacillus farciminis (LF), and the dynamics of protease activity and microbial community were analyzed. Nonprotein-N, free amino acid, ammonia-N, the activities of carboxypeptidase and aminopeptidase, and bacterial diversity were low during NCL ensiling. Exiguobacterium dominated in NCL silage and its relative abundance increased while Enterobacter abundance decreased during ensiling. FA lowered (P < 0.05) pH and coliform bacteria number, while LF increased (P < 0.05) lactic acid bacteria number, lactic acid content and Lactobacillus abundance at the early stage of fermentation. In summary, protein in NCL can be well preserved during ensiling likely due to its low protease and bacterial activity, and FA and LF improve the quality of NCL silage in different ways.

Cloning and characterization of the lignin biosynthesis genes NcCSE and NcHCT from Neolamarckia cadamba.

Neolamarckia cadamba is an important fast growing tree species used for pulping and wood material in industry for it's desirable wood properties. As one of the most important content in wood, lignin provides structural integrity, strength, and hydrophobicity to the thickened cell walls and is the major factor contributing to biomass recalcitrance. It does not reduce the palatability of forage grass for animals, but it hinders the isolation of cellulose fibers and the efficient enzymatic depolymerization of cellulose and hemicellulose into fermentable sugars in biorefining processes by limiting the access by hydrolytic enzymes to their polysaccharide substrates. This work focused on analyzing the functions of NcCSE (Caffeoyl Shikimate Esterase, GenBank accession number: MG739672) and NcHCT (Hydroxycinnamoyl Transferase,GenBank accession number: MG739673) in the lignin biosynthetic process in order to improve the potential for utilization of leaves and wood from N. cadamba. The mutant phenotype of cse-2 was dramatically complemented to WT in the stable transgenic lines cse-35S::NcCSE, but overexpression of NcHCT in the cse-2 mutant did not have the same result as cse-35S::NcCSE, providing only partial complementation.

Dynamics of Bacterial Community and Fermentation Quality during Ensiling of Wilted and Unwilted Moringa oleifera Leaf Silage with or without Lactic Acid Bacterial Inoculants.

To investigate the effects of wilting and lactic acid bacterial inoculants on the fermentation quality and bacterial community of Moringa oleifera leaf silage, fresh and wilted M. oleifera leaves were ensiled with or without Lactobacillus farciminis LF or Lactococcus lactis LL for 1, 7, 14, 30, and 60 days. The results showed that wilting, inoculants, and their interaction exerted significant (P < 0.05) effects on the fermentation characteristics covering dry matter loss, pH value, lactic acid bacterial number, the ratio of lactic acid to acetic acid, and the relative abundances of bacteria, like for species of Lactobacillus, Lactococcus, Pediococcus, Enterococcus, Leuconostoc, and Enterobacter Both LF and LL improved the fermentation quality of wilted and unwilted M. oleifera leaf silage by accelerating lactic acid production and pH decline, decreasing dry matter loss, and inhibiting yeast and coliform bacterial growth through the whole fermentation process. During ensiling, the abundances of Lactococcus, Enterococcus, and Leuconostoc spp. increased from day 1 to day 7 and then declined sharply from day 7 to day 14. Members of these genera and Enterobacter were inhibited, whereas Lactobacillus spp. were enhanced by these two lactic acid bacterial inoculants. The relative abundances of Enterobacter, Enterococcus, and Pediococcus spp. in inoculated silages were relatively low during the whole ensiling process. A lower abundance of Enterobacter spp. was observed in wilted silages than in unwilted silages. In summary, wilting and lactic acid bacterial inoculants had an influence on bacterial community and the fermentation process; LF and LL improved the fermentation quality of wilted and unwilted M. oleifera leaf silage.IMPORTANCEMoringa oleifera leaf is a high-quality feed source for livestock and is increasingly used all over the world. Ensiling might be an effective method for preservation of the leaves. In the practice of silage making, lactic acid bacterial inoculants and wilting are commonly used to improve nutrition preservation. Monitoring the changes in a bacterial community during fermentation gives an insight into understanding and improving the ensiling process. Our results suggest that wilting and lactic acid bacterial inoculants had an influence on the bacterial community and fermentation process of M. oleifera leaf silage. Wilting showed positive effects on silage fermentation by decreasing the abundance of Enterobacter spp., while LF and LL improved the fermentation quality by inhibiting Enterobacter spp. and enhancing Lactobacillus spp. Both LF and LL accelerated the ensiling process from cocci (like Lactococcus, Enterococcus, and Leuconostoc spp.) to lactobacilli.

Genome-wide analysis of the WRKY gene family in drumstick (Moringa oleifera Lam.).

WRKY proteins belong to one of the largest families of transcription factors. They have important functions in plant growth and development, signal transduction and stress responses. However, little information is available regarding the WRKY family in drumstick (Moringa oleifera Lam.). In the present study, we identified 54 MoWRKY genes in this species using genomic data. On the basis of structural features of the proteins they encode, the MoWRKY genes were classified into three main groups, with the second group being further divided into five subgroups. Phylogenetic trees constructed from the sequences of WRKY domains and overall amino acid compositions derived from drumstick and Arabidopsis were similar; the results indicated that the WRKY domain was the main evolutionary unit of WRKY genes. Gene structure and conserved motif analysis showed that genes with similar structures and proteins with similar motif compositions were usually clustered in the same class. Selective pressure analysis indicated that although neutral evolution and positive selection have happened in several MoWRKY genes, most have evolved under strong purifying selection. Moreover, different subgroups had evolved at different rates. The levels of expression of MoWRKY genes in response to five different abiotic stresses (salt, heat, drought, H2O2, cold) were evaluated by reverse transcription polymerase chain reaction (RT-PCR) and quantitative RT-PCR (qRT-PCR), with the results indicating that these genes had different expression levels and that some may be involved in abiotic stress responses. Our results will provide a foundation for cloning genes with specific functions for use in further research and applications.

Bacterial diversity and fermentation quality of Moringa oleifera leaves silage prepared with lactic acid bacteria inoculants and stored at different temperatures.

Four lactic acid bacteria strains (LP, LF, LL, W), isolated and selected from Moringa oleifera leaves (MOL) silage, were identified as Lactobacillus plantarum, L. farciminis, Lactococcus lactis, Weissella thailandensis, respectively. Fermentation quality and bacterial community of MOL ensiled without or with the four strains at 15 °C and 30 °C were investigated. Results showed that all the LAB strains decreased (P < 0.05) the pH and ammonia-N content of MOL silage. Silage stored at 30 °C showed higher (P < 0.05) DM loss, acetic acid and ammonia-N content, and lower LAB count than 15 °C. The environmental temperature also made a great influence on bacterial community of MOL silage. Bacterial diversity was lower and the abundance of Lactobacillus was higher in silages stored at 15 °C. In conclusion, LAB inoculants and a relatively low environmental temperature could be effective to improve the quality of MOL silage.