Integrated transcriptomics and metabolomics reveal specific phenolic and flavonoid accumulation in licorice (Glycyrrhiza uralensis Fisch.) induced by arbuscular mycorrhiza symbiosis under drought stress

Identification of a small secreted protein, PlSSP, that contributes to the symbiotic association of Phomopsis liquidambaris with rice under nitrogen starvation

Endophytic fungi are crucial for enhancing plant growth and stress tolerance. Phomopsis liquidambaris B3, a broad-spectrum endophytic fungus, significantly improves plant nitrogen uptake and growth under nitrogen-limited conditions. In this study, we identified a small secreted protein, PlSSP, which localizes to the cytoplasmic matrix of host cells and modulates plant immune responses. Using proteomic and transcriptomic approaches, we found that PlSSP upregulates key defense-related genes, including members of the PR and WRKY families, as well as genes involved in reactive oxygen species scavenging and nitrogen assimilation. Structural analysis revealed PlSSP's secondary and thermal stability features, which likely contribute to its functional interaction with host cellular components. Functional analyses demonstrated that PlSSP expression correlates with increased fungal colonization and rice biomass accumulation under nitrogen-starved conditions. These results advance our understanding of how P. liquidambaris promotes plant resilience and nutrient uptake, providing insights with potential applications in sustainable agriculture.

Transcriptome Analysis Reveals the Molecular Mechanisms for Mycorrhiza-Enhanced Drought Tolerance in Maize by Regulating the Ca2+ Signaling Pathway

With the continuous change of climate, drought stress has emerged as the primary constraint on crop growth, posing a significant threat to the stability of global grain reserves. Arbuscular mycorrhizal fungi (AMF), as a kind of widely distributed root endophytes, enhance the drought tolerance of maize (Zea mays L.) through regulating the physiological and molecular responses. However, comprehensive transcriptome analysis to reveal the molecular mechanism of drought tolerance in the symbiotic process between AMF and maize is still limited. In the potted plant experiment, maizes inoculated with and without arbuscular mycorrhizal fungus Funneliformis mosseae were grown under well-watered (WW) or drought-stressed (DS) conditions. By using RNA-Seq and transcriptome analysis on maize roots and leaves, this work aimed to investigate the differential expressed genes (DEGs) related to the Ca2+ signaling pathway induced by AMF symbiosis under drought stress. Our findings indicated that F. mosseae inoculation resulted in a decrease in the net fluxes of Ca2+, while simultaneously elevating Ca2+ contents in the maize roots and leaves under well-watered or drought-stressed conditions. Notably, 189 DEGs were regulated not only by AMF symbiosis and drought stress, but also exhibited preferential expression in either leaves or roots. The annotation and enrichment of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that most of the DEGs were significantly enriched in Ca2+ signaling pathway genes, related to signal transduction, cellular process, and defense response. A high number of DEGs with this function (including calcineurin B-like protein (CBL), CBL-interacting protein kinase (CIPK), mitogen-activated protein kinase (MAPK), and calcium-dependent protein kinase (CDPK) receptor kinases) were upregulated-DEGs or downregulated-DEGs in F. mosseae-inoculated maizes under drought stress. Furthermore, some DEGs belong to transcription factor (TF) families, including bHLH ERF, and, MYB, were speculated to play key roles in improving the drought tolerance of maize. Based on the expression data and co-expression analysis between TF and Ca2+ signaling pathway genes, Whirly1 with CBL11, and BRI1-EMS-SUPPRESSOR 1 (BES1) with CBL10, CIPK24, CDPK1, CDPK14, CDPK19, and MAPK9 genes showed significant positive correlations, while B3 domain-containing transcription factors (B3 TFs) with MAPK1 and both CBL9 genes showed significant negative correlations in response to both F. mosseae inoculation and drought stress. The regulation of Ca2+ signaling pathways by AMF symbiosis was an important response mechanism of maize to improve their drought resistance. This study provides insightful perspectives on how AMF-induced modulation of gene expression within the Ca2+ signaling pathway can enhance the drought tolerance of mycorrhizal maize in the future.

Influence of arbuscular mycorrhizal fungi on morpho-biochemical characteristics, nutrient uptake, and transcriptomic profile of Solanum melongena L. plant

The present study was carried out to observe the interaction between Solanum melongena L. with AMF treatments at morphological, biochemical, and molecular levels. The S. melongena plant was inoculated with Funneliformis mosseae, Glomus macrocarpum, Glomus monosporum, Acaulospora koskei, Acaulospora mellea and Rhizophagus irregularis, and also two consortia of F. mosseae + G. monosporum and F. mosseae + G. macrocarpum. Morphological and biochemical parameters such as shoot height, root length, shoot fresh weight, shoot dry weight, fruit fresh weight, fruit dry weight, root fresh weigh, root dry weight, chlorophyll a and b, total soluble sugars, total soluble proteins were examined in this study. Uptake of some essential micronutrients was also analyzed in this study. In transcriptomics experiment, a total of 365 transcripts were commonly upregulated (≥ 1.5x) folds in S. melongena in response to both the AMF isolates, while 44 transcripts were upregulated only in response to G. Macrocarpum and 28 transcripts were upregulated only in response to F. mosseae. KEGG pathway analysis of S. melongena treated with G. macrocarpum revealed carbon metabolism, cofactor biosynthesis and endocytosis as the dominant metabolic pathway, while analysis of F. mosseae treatment revealed glycerophospholipid and endocytosis metabolism as dominant metabolic pathways.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-025-04247-z.

A Mycorrhiza-Induced UDP-Glucosyl Transferase Negatively Regulates the Arbuscular Mycorrhizal Symbiosis

Most terrestrial plants can establish a reciprocal symbiosis with arbuscular mycorrhizal (AM) fungi to cope with adverse environmental stresses. The development of AM symbiosis is energetically costly and needs to be dynamically controlled by plants to maintain the association at mutual beneficial levels. Multiple components involved in the autoregulation of mycorrhiza (AOM) have been recently identified from several plant species; however, the mechanisms underlying the feedback regulation of AM symbiosis remain largely unknown. Here, we report that AM colonization promotes the flavonol biosynthesis pathway in tomato (Solanum lycopersicum), and an AM-specific UDP-glucosyltransferase SlUGT132, which probably has the flavonol glycosylation activity, negatively regulates AM development. SlUGT132 was predominantly expressed in the arbuscule-containing cells, and its knockout or knockdown mutants showed increased soluble sugar content, root colonization level and arbuscule formation. Conversely, overexpression of SlUGT132 resulted in declined soluble sugar content and mycorrhization degree. Metabolomic assay revealed decreased contents of astragalin, tiliroside and cynaroside in slugt132 mycorrhizal roots, but increased accumulation of these flavonoid glycosides in SlUGT132-overexpressing plant roots. Our results highlight the presence of a novel, SlUGT132-mediated AOM mechanism, which enable plants to flexibly control the accumulation of soluble sugars and flavonoid glycosides in mycorrhizal roots and modulate colonization levels.

Three-dimensional fluorescence combined with alternating trilinear decomposition and random forest algorithm for the rapid prediction of species, geographical origin and main components of Glycyrrhizae Radix et Rhizoma (Gancao)

Glycyrrhizae Radix et Rhizoma (Gancao) is a functional food whose quality varies significantly between distinct geographical sources owing to the influence of genetics and the geographical environment. This study employed three-dimensional fluorescence coupled with alternating trilinear decomposition (ATLD) and random forest (RF) algorithms to rapidly predict Gancao species, geographical origins, and primary constituents. Seven fluorescent components were resolved from the three-dimensional fluorescence of the ATLD for subsequent analysis. Results indicated that the RF model distinguished Gancao from various species and origins better than other algorithms, achieving an accuracy of 94.4 % and 88.9 %, respectively. Furthermore, the RF regressor algorithm was used to predict the concentrations of liquiritin and glycyrrhizic acid in Gancao, with 96.4 % and 95.6 % prediction accuracies compared to HPLC, respectively. This approach offers a novel means of objectively evaluating the origin of food and holds substantial promise for food quality assessment.

Special issue: Manipulation/regulation of secondary metabolites in medicinal plants

Medicinal plants, rich sources of valuable natural products with therapeutic potential, play a pivotal role in both traditional and modern medicine. The urgency for mass production and optimized utilization of plant secondary metabolites has intensified, particularly in response to the emergence of diseases following the COVID-19 pandemic. Groundbreaking advancements in genomics and biotechnologies have ushered in a new era of research, transforming our understanding of the biosynthesis, regulation, and manipulation of bioactive molecules in medicinal plants. This special issue serves as a convergence point for a diverse array of original research articles and reviews, collectively aiming to unveil the intricate regulatory mechanisms that govern the biosynthesis of secondary metabolites in medicinal plants. The issue delves into the exploration of the impact of both abiotic and biotic factors on the regulation of plant secondary metabolites. Furthermore, it extends its focus to innovative approaches, such as molecular breeding and synthetic biology, which provide valuable insights into modifying or enhancing the production of secondary metabolites. The special issue leverages cutting-edge techniques, including genomics, metabolomics, and microbiome characterization, to facilitate understanding the multifaceted aspects of specialized metabolism in medicinal plants. As we navigate through this scientific journey, the contributions within this special issue collectively enhance our knowledge and offer potential avenues for optimizing the production of natural products in medicinal plants.