Combined physiological and transcriptome analysis revealed the response mechanism of Pogostemon cablin roots to p-hydroxybenzoic acid

Glutathione's role in mitigating cadmium stress in Pogostemon cablin: Insights from combined transcriptomic and metabolomic approaches

Cadmium (Cd) pollution poses a growing threat to plant growth. Although glutathione (GSH) is recognized for its potential to mitigate Cd-induced stress, its specific effects on alleviating such stress in Pogostemon cablin (patchouli) remain unclear. This study investigated physiological parameters and enzymatic activities across four treatment groups: control (CK), cadmium stress (Cd), glutathione (GSH), and glutathione with cadmium stress (GSH+Cd). Results revealed that chlorophyll a, b, and carotenoid levels in the GSH were approximately 20 % higher than those in the other groups. In contrast, antioxidant enzyme activity in the Cd decreased by about 15 %. Integrated transcriptomic and metabolomic analyses demonstrated that GSH mitigates Cd stress by influencing glycerophospholipid metabolism and flavonoid biosynthesis, with key roles attributed to dgkA1, dgkA2, and CCoAOMT1-4. In conclusion, GSH alleviates Cd stress in P. cablin by enhancing photosynthetic pigment synthesis, reducing reactive oxygen species (ROS) through improved enzymatic activity, and regulating metabolic pathways. These findings provide valuable insights for optimizing the cultivation and management of P. cablin under Cd stress conditions.

Microalgal-based urea wastewater treatment with p-Hydroxybenzoic acid enhances resource recovery and mitigates biological risks from Bisphenol A

Efficient nutrient recovery from source-separated urine is vital for wastewater treatment, with microalgae as a promising solution. However, bisphenol A (BPA) in urine can hinder microalgal resource recovery and pose water quality risks. The role of plant hormones in enhancing microalgal growth and pollutant removal is known, but their impact on BPA-laden urine treatment is not well-studied. Here, we explored para-hydroxybenzoic acid (p-HBA) in Chlorella for treating diluted urine with BPA. p-HBA boosted photosynthesis and glycolysis, increasing pyruvate and ATP production and enhancing microalgal growth by 45.7 %. It also optimized nitrogen metabolism, raising urea and nitrogen consumption by 35 % and 65 %, respectively, and protein content by 23.1 %. Enhanced oxidase and transferase expression improves BPA degradation by 40 %. Additionally, ARGs and plasmid abundance decreased by 24.3 % and 37.5 %, respectively, reducing the risk of ARG dissemination. This study shows that p-HBA significantly improves the efficiency and safety of urine resource recovery, offering a promising strategy for sustainable wastewater treatment.

Genome-Wide Identification of the CIF Gene Family and Protein Interaction with GSO1s Under the p-HBA-Induced Continuous Cropping Obstacle in Pogostemon cablin

Casparian strip integrity factors (CIFs), which are tyrosine-sulfated small peptides, are crucial genes involved in the formation and regulation of the Casparian strip and play an important role in the regulation of plant stress response. In order to explore the evolution, characteristics, role, and function of CIFs in response to continuous cropping obstacles (CCOs), the bioinformatics and gene expression analysis of CIF genes in Pogostemon cablin was carried out by determining the phylogenetic relationship, chromosome location, gene structure, and RT-qPCR results. Results showed that a total of 12 PatCIF family genes were identified on 12 different chromosomes. Promoter prediction analysis revealed 16 different cis-regulatory elements. A systematic evolutionary study of 33 species indicates CIF family genes originated from Spermatophyta. Collinearity analysis revealed P. cablin shared 19 syntenic genes with Solanum lycopersicum and only 8 with Oryza sativa. Transcriptome analysis indicated that the expression of PatCIF1-4 and PatGSO1b/1c/1f genes decreased under p-hydroxybenzoic acid treatment, and further RT-qPCR validation of four PatCIF genes was consistent with the results. AlphaFold prediction showed a protein interaction region between PatCIF1-4 mature peptide and PatGSO1b/1c/1f via the LRR domain, which provides a key binding surface for mature PatCIFs. This study offers a theoretical basis to investigate the roles of PatCIFs and PatGSO1s in CCOs and their protein interactions in P. cablin.

Functional analysis of the PcCDPK5 gene in response to allelopathic substances on p-hydroxybenzoic acid (p-HBA) stress in patchouli

Calcium-dependent protein kinase (CDPK) is an important mediator for Ca2 + signal recognition and transduction, playing a crucial role in plant stress response. Previous studies have shown that PcCDPK5 may be involved in the response of patchouli to p-hydroxybenzoic acid (p-HBA) stress. In this study, we further found that the subcellular localization of PcCDPK5 protein is in the cytoplasm, and its gene expression is closely related to continuous cropping (CC) and p-HBA stress. Under p-HBA stress, silencing the PcCDPK5 homologous gene in Nicotiana tabacum leads to decreased antioxidant enzyme activity and increased malondialdehyde (MDA) content, significantly accumulating reactive oxygen species (ROS) and affecting normal plant growth. On the contrary, overexpression of PcCDPK5 can effectively alleviate the damage caused by p-HBA stress to plant bodies. Through this research, the function of PcCDPK5 in response to p-HBA stress has been preliminarily analyzed, laying a theoretical foundation for alleviating CC obstacles in patchouli.

Continuous cropping of Patchouli alters soil physiochemical properties and rhizosphere microecology revealed by metagenomic sequencing

Continuous cropping (CC) profoundly impacts soil ecosystems, including changes in soil factors and the structure and stability of microbial communities. These factors are interrelated and together affect soil health and plant growth. In this research, metagenomic sequencing was used to explore the effects of CC on physicochemical properties, enzyme activities, microbial community composition, and functional genes of the rhizosphere soil of patchouli. We found that this can lead to changes in various soil factors, including the continuous reduction of pH andNH 4 + -N and the unstable changes of many factors. In addition, S-PPO enzyme activity increased significantly with the cropping years, but S-NAG increased in the first 2 years and decreased in the third cropping year. Metagenomic sequencing results showed that CC significantly changed the diversity and composition of rhizosphere microbial communities. The relative abundance of Pseudomonas and Bacteroides decreased substantially from the phylum level. At the genus level, the number of microbial genera specific to the zero-year cropping (CK) and first (T1), second (T2), and third (T3) years decreased significantly, to 1798, 172, 42, and 44, respectively. The abundance of many functional genes changed, among which COG0823, a gene with the cellular process and signaling functions, significantly increased after CC. In addition,NH 4 + -N, S-CAT, S-LAP, and SOC were the main environmental factors affecting rhizosphere-dominant microbial communities at the phylum level, while pH, SOC, and AK were the key environmental factors affecting rhizosphere functional genes of Pogostemon cablin. In summary, this study showed the dynamic changes of soil factors and rhizosphere microorganisms during CC, providing a theoretical basis for understanding the formation mechanism and prevention of CC obstacles and contributing to the formulation of scientific soil management and fertilization strategies.

Continuous Cropping of Patchouli Alleviate Soil Properties, Enzyme Activities, and Bacterial Community Structures

Pogostemon cablin (Patchouli), an essential medicinal plant in the Lamiaceae family, faces significant challenges under continuous cropping (CC) obstacles. This study examined the rhizospheric soil bacterial communities of patchouli under four different CC years, zero (CK), one (T1), two (T2), and three (T3) years through high-throughput 16S rRNA gene amplicon sequencing. Results showed long-term CC led to significant soil properties and enzyme activity shifts. Key parameters such as soil pH and total potassium (TK) decreased, while ammonium nitrogen (NH4+-N), soil organic carbon (SOC), nitrate nitrogen (NO3--N), available potassium (AK), available phosphorus (AP), total nitrogen (TN), and total phosphorus (TP) increased over the cropping years. Enzyme activities, including ß-glucosidase (ß-GC), polyphenol oxidase (PPO), catalase (CAT), N-acetyl-β-D-glucosaminidase (NAG), and leucine aminopeptidase (LAP), were notably affected. The CC altered the bacterial community structure and composition, reducing the relative abundance of Proteobacteria, Firmicutes, Actinobacteria, and Planctomycetota over time. These findings highlight the impact of CC on patchouli rhizosphere bacteria, providing insights for improved soil management and fertilization strategies in CC systems.

A Genome-Wide Identification and Expression Analysis of the Casparian Strip Membrane Domain Protein-like Gene Family in Pogostemon cablin in Response to p-HBA-Induced Continuous Cropping Obstacles

Casparian strip membrane domain protein-like (CASPL) genes are key genes for the formation and regulation of the Casparian strip and play an important role in plant abiotic stress. However, little research has focused on the members, characteristics, and biological functions of the patchouli PatCASPL gene family. In this study, 156 PatCASPL genes were identified at the whole-genome level. Subcellular localization predicted that 75.6% of PatCASPL proteins reside on the cell membrane. A phylogenetic analysis categorized PatCASPL genes into five subclusters alongside Arabidopsis CASPL genes. In a cis-acting element analysis, a total of 16 different cis-elements were identified, among which the photo-responsive element was the most common in the CASPL gene family. A transcriptome analysis showed that p-hydroxybenzoic acid, an allelopathic autotoxic substance, affected the expression pattern of PatCASPLs, including a total of 27 upregulated genes and 30 down-regulated genes, suggesting that these PatCASPLs may play an important role in the regulation of patchouli continuous cropping obstacles by affecting the formation and integrity of Casparian strip bands. These results provided a theoretical basis for exploring and verifying the function of the patchouli PatCASPL gene family and its role in continuous cropping obstacles.

Antifungal and elicitor activities of p-hydroxybenzoic acid for the control of aflatoxigenic Aspergillus flavus in kiwifruit

Aspergillus flavus not only reduces kiwifruit production but also synthesizes carcinogenic aflatoxins, resulting in a relevant threat to human health. p-Hydroxybenzoic acid (pHBA) is one of the most abundant phenolics in kiwifruit. In this study, pHBA was found to reduce A. flavus mycelial growth by blocking the fungal mitotic exit network (MEN) and cytokinesis and to inhibit the biosynthesis of aflatoxins B1 and B2. The application of pHBA promoted the accumulation of endogenous pHBA and induced oxidative stress in A. flavus-infected kiwifruit, resulting in an increase in H2O2 content and catalase (CAT) and superoxide dismutase (SOD) activities. Preventive and curative treatments with 5 mM pHBA reduced A. flavus advancement by 46.1% and 68.0%, respectively. Collectively, the antifungal and elicitor properties of pHBA were examined for the first time, revealing new insights into the role of pHBA in the defense response of kiwifruit against A. flavus infection.

A Systematic Review on the Continuous Cropping Obstacles and Control Strategies in Medicinal Plants

Continuous cropping (CC) is a common practice in agriculture, and usually causes serious economic losses due to soil degeneration, decreased crop yield and quality, and increased disease incidence, especially in medicinal plants. Continuous cropping obstacles (CCOs) are mainly due to changes in soil microbial communities, nutrient availability, and allelopathic effects. Recently, progressive studies have illustrated the molecular mechanisms of CCOs, and valid strategies to overcome them. Transcriptomic and metabolomics analyses revealed that identified DEGs (differently expressed genes) and metabolites involved in the response to CCOs are involved in various biological processes, including photosynthesis, carbon metabolism, secondary metabolite biosynthesis, and bioactive compounds. Soil improvement is an effective strategy to overcome this problem. Soil amendments can improve the microbial community by increasing the abundance of beneficial microorganisms, soil fertility, and nutrient availability. In this review, we sum up the recent status of the research on CCOs in medicinal plants, the combination of transcriptomic and metabolomics studies, and related control strategies, including uses of soil amendments, crop rotation, and intercropping. Finally, we propose future research trends for understanding CCOs, and strategies to overcome these obstacles and promote sustainable agriculture practices in medicinal plants.

An integrated transcriptome and metabolome analysis reveals the gene network regulating flower development in Pogostemon cablin

Pogostemon cablin is a well-known protected species widely used in medicine and spices, however the underlying molecular mechanisms and metabolite dynamics of P. cablin flower development remain unclear due to the difficulty in achieving flowering in this species. A comparison of the transcriptome and widely targeted metabolome during P. cablin flower development was first performed in this study. Results showed that a total of 13,469 differentially expressed unigenes (DEGs) and 371 differentially accumulated metabolites (DAMs) were identified. Transcriptomic analysis revealed that the DEGs were associated with starch and sucrose metabolism, terpenoid biosynthesis and phenylpropanoid biosynthesis. Among these DEGs, 75 MIKC-MADS unigenes were associated with the development of floral organs. Gibberellins (GAs), auxin, and aging signaling might form a cross-regulatory network to regulate flower development in P. cablin. According to the metabolic profile, the predominant DAMs were amino acids, flavonoids, terpenes, phenols, and their derivatives. The accumulation patterns of these predominant DAMs were closely associated with the flower developmental stage. The integration analysis of DEGs and DAMs indicated that phenylpropanoids, flavonoids, and amino acids might be accumulated due to the activation of starch and sucrose metabolism. Our results provide some important insights for elucidating the reproductive process, floral organ, and color formation of P. cablin flowers at the molecular level. These results will improve our understanding of the molecular and genetic mechanisms involved in the floral development of P. cablin.

Overexpression of GmWRKY172 enhances cadmium tolerance in plants and reduces cadmium accumulation in soybean seeds

INTRODUCTION

Cadmium (Cd) stress is a significant threat to soybean production, and enhancing Cd tolerance in soybean is the focus of this study. The WRKY transcription factor family is associated with abiotic stress response processes. In this study, we aimed to identify a Cd-responsive WRKY transcription factor GmWRKY172 from soybean and investigate its potential for enhancing Cd tolerance in soybean.

METHODS

The characterization of GmWRKY172 involved analyzing its expression pattern, subcellular localization, and transcriptional activity. To assess the impact of GmWRKY172, transgenic Arabidopsis and soybean plants were generated and examined for their tolerance to Cd and Cd content in shoots. Additionally, transgenic soybean plants were evaluated for Cd translocation and various physiological stress indicators. RNA sequencing was performed to identify the potential biological pathways regulated by GmWRKY172.

RESULTS

GmWRKY172 was significantly upregulated by Cd stress, highly expressed in leaves and flowers, and localized to the nucleus with transcriptional activity. Transgenic plants overexpressing GmWRKY172 showed enhanced Cd tolerance and reduced Cd content in shoots compared to WT. Lower Cd translocation from roots to shoots and seeds was also observed in transgenic soybean. Under Cd stress, transgenic soybean accumulated less malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) than WT plants, with higher flavonoid and lignin contents, and peroxidase (POD) activity. RNA sequencing analysis revealed that many stress-related pathways were regulated by GmWRKY172 in transgenic soybean, including flavonoid biosynthesis, cell wall synthesis, and peroxidase activity.

DISCUSSION

Our findings demonstrated that GmWRKY172 enhances Cd tolerance and reduces seed Cd accumulation in soybean by regulating multiple stress-related pathways, and could be a promising candidate for breeding Cd-tolerant and low Cd soybean varieties.