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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. Highlights: HcMDH1 is located in the chloroplasts and could be induced by salt and drought stresses. Expression of the HcMDH1 in yeast improved its survival rate under salt and drought conditions. HcMDH1 can improve salt and drought tolerance ability by changing antioxidant activity. Silencing HcMDH1 reduced salt and drought tolerance by altering the expression of some stress-responsive genes. [ABSTRACT FROM AUTHOR]

In this study, the effects of exogenous methyl jasmonate (MeJA) on metal uptake and its ability to attenuate metal toxicity in kenaf plants under Pb stress were investigated. The experiment was conducted with five different MeJA concentrations (0, 40, 80, 160, and 320 μM) as a foilar application to kenaf plants exposed to 200 μM Pb stress. The results revealed that pretreatmen of MeJA significantly increased plant dry weight, plant height, and root architecture at all concentrations tested, with the most significant increase at 320 μM. Foliar application of MeJA at 160 μM and 320 μM increased the Pb concentrations in leaves and stems as well as the translocation factor (TF) from root to leaf. However, the bioaccumulation factor in the shoot initially decreased and then increased with increasing MeJA concentration. By increasing enzymatic (SOD, POD, and CAT) and non-enzymatic (AsA and non-protein thiols) antioxidants, MeJA pretreatment decreased lipid peroxidation, O2− and H2O2 accumulation and recovered photosynthetic pigment content under Pb stress. Increased osmolytes (proline, sugar, and starch) and protein content after MeJA pretreatment under Pb stress restore cellular homeostasis and improved kenaf tolerance. Our results suggest that MeJA pretreatment modifies the antioxidant machinery of kenaf and inhibits stress-related processes that cause lipid peroxidation, hence enhancing plant tolerance to Pb stress. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. Key message: 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. [ABSTRACT FROM AUTHOR]

Intercropping is considered a sustainable agricultural practice that can reduce the environmental impacts on agriculture. Our study investigated the morphology, physiology, and cadmium (Cd) and lead (Pb) uptake of kenaf (Hibiscus cannabinus L.) and soybean (Glycine max L.) under intercropping in mining soil. Results showed that mutual intercropping is conducive to the growth and biomass accumulation of kenaf and soybean, compared to their respective monoculture. Intercropping increased the relative chlorophyll index in kenaf, while that in soybean had no significant effect. Furthermore, intercropping increased the antioxidant enzyme activity of kenaf, while that of soybean reduced or had no significant effect. The content of malondialdehyde (MDA) was decreased in both of the species. Compared to their respective monoculture, Cd content was increased in kenaf leaves and reduced in soybean roots. Moreover, intercropping decreased the Pb content in tissues of both the species, except that Pb content of kenaf roots was increased. At the same time, root, leaf, or stem bioconcentration factors also performed the same trend, and TF was less than 1. These results indicated that intercropping can increase the plant growth and decrease the metal content in plant tissues. Present findings could provide support for future research on kenaf and soybean cultivation in contaminated lands. In addition, the present study strengthens our understanding about the effectiveness of intercropping system on heavy metal–contaminated lands for sustainable agricultural production. [ABSTRACT FROM AUTHOR]

Soil salinity is one of the most challenging issue for sustainable crop productivity worldwide, and kenaf is an important natural fiber crop with considerable salt tolerance. However, little is known about the molecular mechanisms in kenaf salt tolerance. In this study, 60 kenaf cultivars were screened for salt tolerance, and after analysis of agronomic and physiological indexes, cultivar CP018 and CP047 were found to have the highest and the lowest salt tolerance, respectively. This was mainly demonstrated in the lower root MDA content of 26.78% in CP018 compared to 29.76% in CP047, while the enzyme activities of SOD, POD, and CAT were mostly higher in CP018 than in CP047. Then using these two cultivars CP018 and CP047 as representing salt-tolerant and salt-sensitive cultivars, further global gene expression analysis responses to salt stress were conducted under control (0-mM NaCl) and salt stress (200-mM NaCl) conditions. The result indicated 11,677 (6538 up- and 5139 down-regulated) and 11,764 (6159 up- and 5605 down-regulated) differentially expressed genes (DEGs) in CP018 and CP047, respectively. Transcription factors including WRKY, LBD, HSF, and NAC, most of which were up-regulated in CP018 compared with CP047. KEGG enrichment analysis identified significantly different gene expression related to metabolic pathways, such as ROS scavenging, sucrose and starch metabolism, plant hormone signal transduction, cysteine and methionine metabolism, phenylpropane, and flavonoid biosynthesis in both cultivars, and these pathways may be partly responsible for the differences in salt tolerance between CP018 and CP047. These findings may help to elucidate the molecular mechanisms of salt tolerance in kenaf. [ABSTRACT FROM AUTHOR]

Ethylene response factors (ERF) are members of the APETALA2/ERF transcription factor family, and they play an important role in plant growth, development, and response to various environmental stresses. In this study, an ERF transcription factor HcERF4 was isolated and characterized from kenaf. The results showed HcERF4 contained an open reading frame of 702 bp, which comprised of single AP2 domain. Subcellular localization analysis revealed that the HcERF4 gene was localized in the nucleus and cytoplasm. Transactivation assays in yeast demonstrated that HcERF4 functions as a transcriptional activator. Its expression profile was investigated by real-time PCR analysis in different tissues and under salt as well as drought stress condition. The result revealed that HcERF4 could be markedly induced by salt and drought in a time and concentration dependent manner. Moreover, silencing of HcERF4 by using the VIGS technique, caused a significant growth inhibition under salt or drought stress condition, with lower plant height, stem diameter, and fresh weight, indicating HcERF4 plays key roles response abiotic stress. In addition, physiological index analyses showed that the contents of MDA, O2−, H2O2, and free proline significantly increased, while the activities of antioxidant enzymes were significantly restrained in HcERF4 silenced plants. Furthermore, the expression level of eight important genes involved in plant growth regulation, including HcERF3, HcNAC29, HcSOD, HcP5CS, HcbZIP43, HcWRKY31, HcMYB44, and HcCBP25 were investigated, and the result showed that all eight genes were highly expressed in the leaves of the wild kenaf, but were significantly downregulated in the leaves of the VIGS kenaf plants under drought and salt stress conditions; Consequently, the present results indicate HcERF4 plays a positive role in regulating salt and drought stress in kenaf. Key message: HcERF4 transcription factor modulates drought and salinity stress in kenaf (Hibiscus cannabinus L.). [ABSTRACT FROM AUTHOR]

Key message: Numbers of critical genes and pathways were found from the levels of transcriptome and metabolome, which were useful information for understanding of kenaf CMS mechanism. Cytoplasmic male sterility (CMS) is a maternally inherited trait in higher plants that leads to the inability to produce or release functional pollen. However, there is lack of comprehensive studies to reveal the molecular basis of CMS occurrence in kenaf. Herein, we performed transcriptome and UPLC-MS-based metabolome analyses in the anthers of a CMS (UG93A) and its maintainer (UG93B) to sort out essential genes and metabolites responding to CMS in kenaf. Transcriptome characterized 7769 differentially expressed genes (DEGs) between these two materials, and pathway enrichment analysis indicated that these DEGs were involved mainly in pentose and glucuronate interconversions, starch and sucrose metabolism, taurine and hypotaurine metabolism. In the metabolome assay, a total of 116 significantly different metabolites (SDMs) were identified between the CMS and its maintainer line, and these SDMs were involved in eight KEGG pathways, including flavone and flavonol biosynthesis, glycerophospholipid metabolism, flavonoid biosynthesis, glycosylphosphatidylinositol-anchor biosynthesi. Integrated analyses of transcriptome and metabolome showed that 50 genes had strong correlation coefficient values (R2 > 0.9) with ten metabolites enriched in six pathways; notably, most genes and metabolites of flavonoid biosynthesis pathways and flavone and flavonol biosynthesis pathways involved in flavonoids biosynthetic pathways were downregulated in CMS compared to those in maintainer. Taken together, the decreased accumulation of flavonoids resulted from the compromised biosynthesis pathways coupled with energy deficiency in the anthers may contribute largely to CMS in UG93A of kenaf. [ABSTRACT FROM AUTHOR]