Cadmium (Cd) is a widespread environmental pollutant that severely threatens crop productivity and food safety. However, the regulatory mechanisms underlying Cd detoxification and tolerance in sorghum remain largely elusive. Herein, we functionally characterized SbWRKY6, a Cd‑induced WRKY transcription factor that localizes to the nucleus and functions as a transcriptional activator. Stable overexpression of SbWRKY6 significantly enhanced Cd tolerance in sorghum, as evidenced by improved growth performance, mitigated oxidative damage, and decreased Cd concentration in plant tissues, whereas silencing of SbWRKY6 resulted in a Cd-hypersensitive phenotype with exacerbated toxicity symptoms. Mechanistically, we identified SbPLAC8-17, a member of the Plant Cadmium Resistance (PCR)/PLAC8 family, as a critical downstream target of SbWRKY6. Heterologous expression of SbPLAC8-17 functionally complemented the Cd‑sensitive phenotype of the yeast mutant ∆ycf1 and reduced intracellular Cd accumulation. Further yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA), and dual-luciferase reporter (Dual-LUC) assays confirmed that SbWRKY6 directly binds to the SbPLAC8-17 promoter and transcriptionally activates its expression. In vivo silencing of SbPLAC8-17 significantly impaired cellular Cd²⁺ efflux and aggravated Cd toxicity in sorghum. Additionally, the rapid Cd-induced transcriptional upregulation of SbMPK3 and its direct physical interaction with SbWRKY6 suggest a potential upstream regulatory module that remains to be functionally validated. Collectively, this study elucidates a novel SbWRKY6‑SbPLAC8-17 transcriptional cascade that positively regulates Cd tolerance by facilitating Cd²⁺ efflux, providing promising genetic targets for phytoremediation and molecular breeding of safe sorghum cultivars for Cd-contaminated fields.

Cadmium (Cd) stress severely compromises crop growth and yields globally. The APETALA2/Ethylene-Responsive Factor (AP2/ERF) family is essential in modulating plant tolerance to Cd. However, the molecular mechanisms governing AP2/ERF-driven adaptation to Cd stress in kenaf have remained largely unexplored. This study identified 213 HcAP2/ERF members within the kenaf genome and classified them into 11 distinct groups. Notably, nuclear-localized HcERF37 was significantly induced upon CdCl2 exposure. Overexpression of HcERF37 in Arabidopsis markedly enhanced Cd tolerance, as evidenced by improved seed germination, seedling growth, and antioxidant capacity, alongside reduced Cd accumulation. Conversely, silencing HcERF37 in kenaf exacerbated Cd toxicity, resulting in substantial transcriptional reprogramming of stress-responsive genes. Mechanistic studies revealed that HcERF37 binds to the promoter of HcPDR1, facilitating Cd2+ extrusion from cells and thereby improving Cd tolerance. These findings reveal a novel regulatory axis, HcERF37-HcPDR1, providing valuable genetic resources for the development of Cd stress-resilient crops.

With the rapid growth of industry and increasing population pressure, environmental pollution has become a serious issue, causing ecosystem disruption and posing significant risks to human health. Consequently, there is a growing need to explore sustainable resources for environmental protection. Present study focuses on multipurpose bast fiber crops, including kenaf, hemp, ramie, jute, and flax, which are known for their environmental benefits. A comprehensive literature review was conducted, using keywords such as bast fiber crops, sustainable environmental remediation, and phytoremediation. This review examines the environmental benefits of bast fiber crops particularly their role in carbon sequestration, desertification mitigation, atmospheric purification, and utilization of problematic lands. Bast fiber plants offer potential for phytoremediation, aiding in the restoration of polluted soils and wastewater. The selected bast fiber crops were chosen based on their widespread cultivation, environmental resilience, and potential contributions to eco-friendly solutions. This review highlights the key results, emphasizing that these crops provide sustainable substitutes for land rehabilitation, climate change mitigation, and the promotion of green bioenergy, contributing to a more sustainable and healthier environment.

Salicylic acid (SA) plays a crucial role in alleviating drought stress in plants. However, little is known about the molecular mechanisms underlying exogenous SA on the drought tolerance of kenaf. In this study, the kenaf seedlings were subjected to physiological and transcriptomic analysis under control (CK), moderate drought stress (D), and moderate drought stress with 1 mM SA (D_SA). Under drought conditions, SA significantly improved the plant biomass, leaf area, antioxidant enzyme activities (SOD, POD, and CAT), soluble sugars, starch and proline contents, and photosynthesis, while the contents of MDA, H2O2, and O2- were significantly decreased. A total of 3430 (1118 up-regulated and 2312 down-regulated) genes were differentially expressed in group D, compared with group CK. At the same time, 92 (56 up-regulated and 36 down-regulated) genes were differentially expressed in group D_SA compared with group D. GO and KEGG analysis showed that the differentially expressed genes (DEGs) were enriched in various metabolic pathways, such as carbohydrate metabolism, lipid metabolism, and the metabolism of terpenoids and polyketides. Results showed that the genes related to the antioxidant system, sucrose and starch synthesis, osmoregulation, ABA signal regulation, and differentially expressed transcription factors, such as AP2/ERF4 and NF-Y1, were involved in the increased drought tolerance of kenaf under exogenous SA. Virus-induced gene silencing (VIGS)-mediated silencing of salicylate binding protein 2 gene (HcSABP2) decreased the drought resistance of kenaf seedlings. Thus, the present study provides valuable insights into the regulatory mechanism of exogenous SA in alleviating drought stress in kenaf.

Drought and salt stress are two important environmental factors that significantly restrict plant growth and reproduction. Malate dehydrogenase is essential to life as it is engaged in numerous physiological processes in cells, particularly those related to abiotic stress reactions. However, a complete understanding of MDH family members in kenaf is not clear yet. In this study, subcellular localization analysis and a yeast transcriptional activation assay revealed that HcMDH1 was localized in chloroplasts but had no transcriptional activation activity. When exposed to salt or drought stress, yeast cells expressing the HcMDH1 gene exhibit an increased survival rate. Overexpression of HcMDH1 in Arabidopsis increased seed germination rate and root growth when transgenic lines were exposed to varying concentrations of mannitol and NaCl. Subsequent physiological studies revealed that transgenic lines had higher concentrations of soluble carbohydrates, proline, and chlorophyll and lower concentrations of malondialdehyde (MDA) and reactive oxygen species (ROS). Furthermore, inhibiting HcMDH1 in kenaf using virus-induced gene silencing (VIGS) decreased salt and drought tolerance due to elevated ROS and MDA levels. In these silenced lines, the expression of six essential genes engaged in stress-resistance and photosynthesis, namely HcGAPDH, HcGLYK, HcFBA, HcFBPase, HcPGA, and HcLSD, is significantly altered under salt and drought stress. In summary, HcMDH1 is a complex and positive regulatory gene that plays a key role in regulating chlorophyll content, antioxidant enzyme activity and osmotic regulation under salt and drought stress, which may have implications for kenaf transgenic breeding.

Drought is one of the important factors limiting crop growth. Plants can enhance resistance to various stressors by forming symbiotic relationships with arbuscular mycorrhizal fungi (AMF). However, the regulatory mechanism of AMF on the drought tolerance of kenaf remains unclear. Therefore, we studied the effects of inoculating Claroideoglomus etunicatum (C. etunicatum, Ce) on the growth, gaseous exchange, antioxidant enzymes activity, osmotic regulatory substances, endogenous hormones, elemental content, and drought resistance related gene expression in kenaf under different water conditions, as well as the changes in soil enzymes after inoculation with Claroideoglomus etunicatum (Ce). The results showed that the biomass of kenaf inoculated with AMF significantly increased under drought conditions; For the aboveground parts of kenaf, inoculation with AMF improved the gas exchange parameters, and synthesized more osmotic regulatory substances to resist drought stress. At the same time, AMF also enhanced the scavenging ability of reactive oxygen species and reducing the cell damage caused by ROS; For the root of kenaf, AMF promoted the root development, enhanced the ability of plant element and water absorption, and significantly increased the content of IAA and ABA in the roots of kenaf under drought stress, reaching 26.45

Kenaf is considered to have great potential for remediation of heavy metals in ecosystems. However, studies on molecular mechanisms of root Cd accumulation and tolerance are still inadequate. In this study, two differently tolerant kenaf cultivars were selected as materials and the physiological and transcriptomic effects were evaluated under Cd stress. This study showed that 200 mu mol/L CdCl 2 treatment triggered the reactive oxygen species (ROS) explosion and membrane lipid peroxidation. Compared with the Cd-sensitive cultivar 'Z', the Cd-tolerant cultivar 'F' was able to resist oxidative stress in cells by producing higher antioxidant enzyme activities and increasing the contents of ascorbic acid (AsA) and glutathione (GSH). The root cell wall of 'F' exhibited higher polysaccharide contents under Cd treatment, providing more Cd-binding sites. There were 3,439 differentially expressed genes (DEGs) that were co-regulated by Cd treatment in two cultivars. Phenylpropanoid biosynthesis and plant hormone signal transduction pathways were significantly enriched by functional annotation analysis. DEGs associated with pectin, cellulose, and hemi-cellulose metabolism were involved in Cd chelation of root cell wall; V-ATPases, ABCC3 and Narmp3 could participated in vacuolar compartmentalization of Cd; PDR1 was responsible for Cd efflux; the organic acid transporters contributed to the absorption of Cd in soil. These genes might have played key roles in kenaf Cd tolerance and Cd accumulation. Moreover, HcZIP2 was identified to be involved in Cd uptake and transport in kenaf. Our findings provide a deeper understanding of the molecular pathways underlying Cd accumulation and detoxification mechanisms in kenaf.

High salinity is an abiotic stress that limits crop production. Kenaf (Hibiscus cannabinus L.) is an annual fiber crop of the genus Hibiscus in the family Malvaceae with a certain tolerance to salt stress. Seed priming has been shown to ameliorate the adverse effects of salt stress on plants. However, the salt resistance mechanism in kenaf seeds treated with priming agents is not fully understood. In this study, we used four priming agents (H2O, PEG, ABA, KNO3) in different concentrations to treat kenaf seeds, and subjected the induced kenaf seedlings to salt stress (150 mM NaCl) to measure their agronomic traits and physiological and biochemical indicators. Our results indicate that the optimal priming concentration for PEG was 10

Among plants' transcription factor families, the bHLHs family has a significant influence on plant development processes and stress tolerance. However, there have been no relevant studies performed on the bHLHs family in kenaf (Hibiscus cannabinus L). Here, the bHLH transcription factors in kenaf were found using bioinformatics, and a total of 141 kenaf HcbHLH transcription factors were identified. Phylogenetic analysis revealed that these transcription factors were irregularly distributed on 18 chromosomes and separated into 20 subfamilies. Additionally, utilizing the transcriptome data under diverse abiotic pressures, the expression of HcbHLH members was analyzed under different stress conditions. A typical HcbHLH abiotic stress transcription factor, HcbHLH88, was exposed to salt, drought, heavy metals, and ABA. The findings revealed that HcbHLH88 might be activated under salt, drought, cadmium stress, and ABA conditions. Furthermore, HcbHLH88's function under salt stress conditions was studied after it was silenced using the virus-induced gene silencing (VIGS) technique. Reduced antioxidant enzyme activity and stunted plant development were seen in VIGS-silenced seedlings. Stress-related genes were shown to be considerably downregulated in the HcbHLH88-silenced kenaf plants, according to the qRT-PCR study. In conclusion, this study provides the first systematic gene family analysis of the kenaf bHLH gene family and provides a preliminary validation of the salt tolerance function of the HcbHLH88 gene. This study lays the foundation for future research on the regulatory mechanisms of bHLH genes in response to abiotic stresses.

Nitric oxide (NO) extensively participates in regulating plant growth and abiotic stress. However, the potential effects of NO on alleviating cadmium (Cd) toxicity in kenaf (Hibiscus cannabinus L.) remain poorly understood. Herein, kenaf seedlings were pretreated hydroponically with 150 mu M sodium nitroprusside (NO donor) for 4 days, followed by 15 days of treatment with 200 mu M CdCl2 & sdot;2.5 H2O. In this study, Cd stress adversely impaired seedling growth, triggering oxidative stress and dramatically increased Cd accumulation in both shoots and roots. However, exogenous NO remarkably improved Cd tolerance in kenaf seedlings. NO pretreatment significantly enhanced the activities of antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and glutathione reductase (GR)) and the contents of proline, soluble protein, and chlorophyll b (Chl b) upon Cd exposure, which contributed to ameliorate Cd-induced oxidative injury. Under Cd stress, NO increased the contents of cell wall polysaccharides (water-soluble pectin (WSP), alkali-soluble pectin (ASP), and hemicellulose 1 (HC1)) and the abundance of negatively charged functional groups, thereby promoting Cd deposition in root cell wall. Transcriptome analysis further revealed that differentially expressed genes (DEGs) involved in cell wall biosynthesis, ROS metabolism and signal transduction, and nitrogen and sulfur metabolism played vital roles in NO-mediated Cd detoxification. ZIP1, ZIP5, ABCG8, ABCC14, CAX18, VIT4, and HIPP20 transporters were determined to be involved in Cd absorption and transport during the process of NO mitigating Cd stress. Moreover, HcERF.C3 gene was proved to have a positive impact on Cd tolerance and Cd homeostasis through virus-induced gene silencing analysis. These findings provide a deeper understanding of NO alleviating Cd phytotoxicity and a basis for improving phytoremediation.

Kenaf (Hibiscus cannabinus L.) is an important fiber crop, which can be applied for the restoration of saline-alkali land. The objective of our study was to investigate the impacts of exogenous glutathione (GSH) on physiological and biochemical properties, ion balance, and DNA methylation of kenaf under salt stress. We used Hoagland nutrient solution containing 200 mM NaCl to simulate salt stress, and found the growth of kenaf seedlings was substantially hindered. 100 μM GSH pretreatment effectively increased the plant height, stem diameter, main root length, and fresh weight under salt stress, as well as reduced the uptake of Na+ and Cl− and promoted the uptake of K+. Besides, exogenous GSH pretreatment protected kenaf plants from salt-induced adversities by reducing the ROS-induced oxidative damage, enhancing the contents of chlorophyll, proline, and soluble sugar. Salinity reduced the total DNA methylation level in kenaf genome, triggering higher mRNA expressions of HcGLP3, HcDOF1.4, HcULP3, HcVHA, HcPP2C39, and HcSRF6. However, GSH addition enhanced the total DNA methylation level. We further utilized virus-induced genes silencing technique to confirm that HcGLP3 played a positive role in the response of kenaf to salinity. Taken together, exogenous GSH could enhance salt tolerance in kenaf by mediating modulation of oxidative stress response and DNA methylation.

Late embryogenesis abundant (LEA) proteins have been widely recognized for their role in various abiotic stress responses in higher plants. Nevertheless, the specific mechanism responsible for the function of LEA proteins in plants has not yet been explored. This research involved the isolation and characterization of HcLEA113 from kenaf, revealing a significant increase in its expression in response to drought stress. When HcLEA113 was introduced into yeast, it resulted in an improved survival rate under drought conditions. Furthermore, the overexpression of HcLEA113 in tobacco plants led to enhanced tolerance to drought stress. Specifically, HcLEA113-OE plants exhibited higher germination rates, longer root lengths, greater chlorophyll content, and higher relative water content under drought stress compared to wild-type (WT) plants, while their relative conductivity was significantly lower than that of WT plants. Further physiological measurements revealed that the proline content, soluble sugars, and antioxidant activities of WT and HcLEA113-OE tobacco leaves increased significantly under drought stress, with greater changes in HcLEA113-OE plants than WT. The increase in hydrogen peroxide (H2O2), superoxide anions (O-2(-)), and malondialdehyde (MDA) content was significantly lower in HcLEA113-OE lines than in WT plants. Additionally, HcLEA113-OE plants can activate reactive oxygen species (ROS)- and osmotic-related genes in response to drought stress. On the other hand, silencing the HcLEA113 gene through virus-induced gene silencing (VIGS) in kenaf plants led to notable growth suppression when exposed to drought conditions, manifesting as decreased plant height and dry weight. Meanwhile, antioxidant enzymes' activity significantly decreased and the ROS content increased. This study offers valuable insights for future research on the genetic engineering of drought resistance in plants.

Light is a basic requirement to drive carbon metabolism in plants and supports life on earth. Spectral quality greatly affects plant morphology, physiology, and metabolism of various biochemical pathways. Among visible light spectrum, red, blue, and green light wavelengths affect several mechanisms to contribute in plant growth and productivity. In addition, supplementation of red, blue, or green light with other wavelengths showed vivid effects on the plant biology. However, response of plants differs in different species and growing conditions. This review article provides a detailed view and interpretation of existing knowledge and clarifies underlying mechanisms that how red, blue, and green light spectra affect plant morpho-physiological, biochemical, and molecular parameters to make a significant contribution towards improved crop production, fruit quality, disease control, phytoremediation potential, and resource use efficiency.

Salinity affects plant growth, alters physiology and causes changes in DNA methylation. However, complete understanding of DNA methylation mechanism in response to salt stress remains unclear. Kenaf seedlings were pre-treated with 0, 50, 100, 150, and 200 µM of the DNA methylation inhibitor 5-azacytidine (5-azaC) for 7 days, and exposed to uniform NaCl concentration (150 mM) in nutrient solution for 9 days. Morpho-physiological, hormonal, and ultrastructural changes of leaves and DNA methylation sequencing were investigated, and function of DNA demethylase gene HcROS1 was verified by virusinduced gene silencing (VIGS) technology. Pretreatment with 5-azaC alleviated salt stress in kenaf, significantly increased the seedlings biomass, antioxidant enzyme activities, and contents of chlorophyll and carbohydrates while, reduced ROS production. Furthermore, 150 µM 5-azaC pretreatment relieved salt stress damage to cell ultrastructure, particularly chloroplast structure, whose lamellar structure was neatly stacked. Methylome analysis showed that 5-azaC pretreatment significantly reduced genomic DNA methylation, and a total of 441 differentially methylated genes (DMGs) were detected in 5-azaC150, of which 186 and 255 were characterized as up- and down- regulated DMGs, respectively. DMGs HcMDH, pyruvate kinase, triosephosphate isomerase, G6PDH, NADPH, and Hsps are mainly involved in carbon metabolism, amino acid biosynthesis, and fatty acid metabolism were characterized as differentially expressed genes (DEGs). Moreover, silencing HcROS1 could significantly increased the sensitivity of kenaf seedlings to salt. 5-azaC pretreatment altered physiological indexes, reduced DNA methylation levels, and improved kenaf salt tolerance. Furthermore, HcROS1 can positively regulate kenaf’s response to salt stress.

Crop lodging is recognised as one of the yield-limiting factors in agricultural production. Therefore, better understanding to improve lodging resistance and to prevent lodging-induced losses in agronomic crops is necessary. Besides yield losses, lodging severely affects the crop harvesting process and increases the production cost. However, achieving the objective of higher crop yields and yield quality without increasing lodging risk is quite challenging. To this end, it is essential to interpret the underlying mechanism of plant stem buckling and failure of root anchorage and optimise the fundamental trade-off between lodging resistance and yield performance in agronomic crops. In the present review, we made an effort to discuss recent and innovative research insights that guarantee greater lodging resistance along with advanced lodging prevention strategies while sustaining higher crop yield and yield quality.

Salinity stress limits agricultural production. The DNA methyltransferase inhibitor, 5-azacitidine (5-azaC), plays a role in plant abiotic stress regulation, but its molecular basis in mediating salinity tolerance in kenaf remains unclear. To investigate the effects on 5-azaC on alleviating salt stress, kenaf seedlings were pre-treated with 0, 50, 100, 150, and 200 μM 5-azaC and then exposed to 150 mM NaCl in a nutrient solution. Physiological, transcriptomic, and proteomic analyses were conducted on the root system to understand the regulatory mechanism of 5-azaC (comparing 5-azaC150 and control group 5-azaC0) under salt stress. The results indicated that 5-azaC significantly mitigated salt stress in kenaf by activating the antioxidant system, reducing reactive oxygen species (ROS), and increasing starch, soluble sugars, and adenosine triphosphate (ATP) content. A total of 14,348 differentially expressed genes (DEGs) and 313 differentially abundant proteins (DAPs) were identified. Combined proteomic and transcriptomic analysis revealed 27 DEGs/DAPs, with jointly up-regulated proteins (genes) including HcTHI1, HcBGLU11, and HcCBL1, and jointly down-regulated proteins (genes) including HcGAPDH, HcSS, and HcPP2C52. Overexpression and virus-induced gene silencing (VIGS) of HcPP2C52 demonstrated its role as a negative regulator of salt tolerance. These findings provide insights into the regulatory role of 5-azaC in plant responses to abiotic stresses. SIGNIFICANCE: The specific molecular mechanism by which 5-azaC affects gene expression and protein activity of kenaf has been revealed, leading to enhanced salt tolerance.

Soybean sucrose transporter GmSUT4 regulated plant growth and development through sugar metabolism

Soil heavy metal pollution has become a worldwide environmental issue; however, remediation of contaminated soils using biochar could be an eco-friendly approach to rehabilitate these soils by reducing their adverse effects. A pot experiment was carried out to determine the effectiveness of biochar derived from corn straw (CSB) at different application rates (0

CUP-SHAPED COTYLEDON (CUC) transcription factors have a central regulatory function in plant growth and development. However, their involvement in kenaf (Hibiscus cannabinus L.) remains largely unexplored. In this study, we conducted a comprehensive analysis to identify six HcCUC genes in the kenaf genome. Through bioinformatic analysis, we found that the kenaf HcCUC genes share similar motifs and highly conserved gene structures. Phylogenetic analysis categorized the six HcCUC genes into two groups, that shared similarities with CUC2 or CUC3 genes from other species. Collinearity analysis revealed the formation of 6 syntenic gene pairs among the HcCUC genes, and 8 homologous gene pairs with three AtCUC genes from Arabidopsis. To investigate tissue-specific expression, we analyzed transcriptome data, that showed differential expression of HcCUC genes, particularly in leaves during the seedling stage, buds during the maturation stage, and anthers at the dual-core period. Functional characterization of HcCUC1 was achieved through its overexpression in Arabidopsis, resulting in elongated cotyledons, absent of petioles and increased number of rosette leaf and lateral branches. qRT-PCR analysis revealed that HcCUC1 potentially influences leaf and lateral branch development by up-regulating the expression of auxin-related genes (AtYUC2, AtYUC4, AtPIN1, AtPIN3, AtPIN4) and leaf shape-related genes (AtKNAT2, AtKNAT6). Notably, overexpression of HcCUC1 down-regulated the expression of flowering-related genes (AtFT, AtAP1, AtLFY, AtFUL), causing delayed flowering. Overall, our findings emphasize the pivotal role of HcCUC1 in regulating leaf and lateral branch growth, development, and flowering time, provide valuable insights into the function and genetic regulation of HcCUC genes. Six HcCUC genes were identified in the kenaf genome, with HcCUC1 playing a role in regulating leaf and lateral branch growth and development, as well as flowering time.