The hemibiotrophic bacterial pathogen Pseudomonas syringae infects a range of plant species and causes enormous economic losses. Auxin and WRKY transcription factors play crucial roles in plant responses to P. syringae, but their functional relationship in plant immunity remains unclear. Here, we characterized tomato (Solanum lycopersicum) SlWRKY75, which promotes defenses against P. syringae pv. tomato (Pst) DC3000 by regulating plant auxin homeostasis. Overexpressing SlWRKY75 resulted in low free indole-3-acetic acid (IAA) levels, leading to attenuated auxin signaling, decreased expansin transcript levels, upregulated expression of PATHOGENESIS-RELATED GENES (PRs) and NONEXPRESSOR OF PATHOGENESIS-RELATED GENE 1 (NPR1), and enhanced tomato defenses against Pst DC3000. RNA interference-mediated repression of SlWRKY75 increased tomato susceptibility to Pst DC3000. Yeast one-hybrid, electrophoretic mobility shift assays, and luciferase activity assays suggested that SlWRKY75 directly activates the expression of GRETCHEN HAGEN 3.3 (SlGH3.3), which encodes an IAA-amido synthetase. SlGH3.3 enhanced tomato defense against Pst DC3000 by converting free IAA to the aspartic acid (Asp)-conjugated form IAA-Asp. In addition, SlWRKY75 interacted with a tomato valine-glutamine (VQ) motif-containing protein 16 (SlVQ16) in vivo and in vitro. SlVQ16 enhanced SlWRKY75-mediated transcriptional activation of SlGH3.3 and promoted tomato defense responses to Pst DC3000. Our findings illuminate a mechanism in which the SlVQ16–SlWRKY75 complex participates in tomato pathogen defense by positively regulating SlGH3.3-mediated auxin homeostasis.

Tobacco bacterial wilt caused by Ralstonia solanacearum is one of the most devastating diseases. Microbial keystone taxa were proposed as promising targets in plant disease control. In this study, we obtained an antagonistic Bacillus isolate EM-1 from bacterial wilt-suppressive soil, and it was considered rhizosphere-resident bacteria based on high (100%) 16S rRNA gene similarity to sequences derived from high-throughput amplicon sequencing. According to 16S rRNA gene sequencing and MLSA, strain EM-1 was identified as Bacillus velezensis. This strain could inhibit the growth of R. solanacearum, reduce the colonization of R. solanacearum in tobacco roots, and decrease the incidence of bacterial wilt disease. In addition, strain EM-1 also showed a strong inhibitory effect on other phytopathogens, such as Alternaria alternata and Phytophthora nicotianae, indicating a wide antagonistic spectrum. The antimicrobial ability of EM-1 can be attributed to its volatile, lipopeptide and polyketide metabolites. Iturin A (C14, C15, and C16) was the main lipopeptide, and macrolactin A and macrolactin W were the main polyketides in the fermentation broth of EM-1, while heptanone and its derivatives were dominant among the volatile organic compounds. Among them, heptanones and macrolactins, but not iturins, might be the main potential antibacterial substances. Complete genome sequencing was performed, and the biosynthetic gene clusters responsible for iturin A and macrolactin were identified. Moreover, strain EM-1 can also induce plant resistance by increasing the activity of CAT and PPO in tobacco. These results indicated that EM-1 can serve as a biocontrol Bacillus strain for tobacco bacterial wilt control. This study provides a better insight into the strategy of exploring biocontrol agent based on rhizosphere microbiome.

Symbiotic associations between leguminous plants and their nodule microbiome play a key role in sustainable agriculture by facilitating the fixation of atmospheric nitrogen and enhancing plant stress resistance. This study aimed to decipher the root nodule microbiome of two halophytic legumes, Sesbania cannabina and Glycine soja, which grow in saline soils of the Yellow River Delta, China, using PacBio’s circular consensus sequencing for full-length bacterial 16S rRNA gene to obtain finer taxonomic information. The cultivated legume Glycine max was used for comparison. We identified 18 bacterial genera and 55 species in nodule samples, which mainly classified to Proteobacteria, and rhizobial genus Ensifer was the predominant group. The three legumes showed similarity in operational taxonomic unit (OTU) diversity but distinction in OTU richness, indicating that they harbor similar bacterial species with different relative contents. The results of principal coordinates analysis and ANOSIM tests indicated that G. soja and G. max have similar nodule bacterial communities, and these communities differ from that of S. cannabina. Wild legumes S. cannabina and G. soja both harbored a higher number of rhizobia, while G. max possessed more non-rhizobial bacteria. These differences could be associated with their adaptability to saline–alkali stress and revealed clues on the nodule endophytes with relative importance of culturable rhizobial symbionts.

Sorghum (Sorghum bicolor) is the fifth most important cereal crop in the world. It is an annual C4 crop due to its high biomass and wide usage, and has a strong resistance to stress. Obviously, there are many benefits of planting sorghum on marginal soils such as saline-alkali land. Although it is known that abscisic acid (ABA) is involved in plant abiotic stress responses, there are few reports on sorghum. Here, we obtained RNA-seq data, which showed gene expression at the genome-wide level under saline-alkali stress. The genes related to ABA biosynthesis, catabolism, and signaling were identified and analyzed. Meanwhile, their amino acid sequences were intermingled with rice genes to form several distinct orthologous and paralogous groups. ABA-related differentially expressed genes under saline-alkali stress were identified, and family members involved in ABA signaling were hypothesized based on the expression levels and homologous genes in rice. Furthermore, the ABA signaling pathway in Sorghum bicolor was understood better by interaction analysis. These findings present a comprehensive overview of the genes regulating ABA biosynthesis, catabolism, and signaling in Sorghum bicolor under saline-alkali stress, and provide a foundation for future research regarding their biological roles in sorghum stress tolerance.

Salt and alkali stress are major constraints on soybean productivity, but their distinct impacts during early development remain insufficiently understood. Wild soybean (Glycine soja), a valuable genetic resource for stress tolerance, was evaluated under salt (0.6% and 1.2% NaCl) and alkali (pH 9.16) stress by assessing germination, seedling traits, ion accumulation, and transcriptomic responses. Salt stress permitted partial germination, whereas alkali stress completely suppressed radicle emergence. Seedling growth and height showed tolerance under salinity, but high pH caused severe wilting and mortality. Ion profiling revealed root Na⁺ sequestration with stem K⁺ buffering in salinity, whereas alkali stress confined Na⁺ to roots, maintaining the highest stem K⁺/Na⁺ ratio. Bioaccumulation and translocation factors peaked at 0.6% NaCl in wild soybean. Transcriptome analysis identified 7,355 DEGs grouped into five clusters, enriched in phenylpropanoid/flavonoid biosynthesis and hormone signaling. Salt stress upregulated genes including FLS, F3H, and F3′5′H, whereas alkali stress induced CHS, peroxidase, and CYP75B1. Ion transport regulation differed, with HKT1 and KT11 activated under salinity and NIP5–1 under alkalinity. Among 385 TF-related DEGs, MYB, ERF, bHLH, and WRKY dominated (67% of total), with complex TF-gene networks observed under salt stress. Exogenous flavonoids (rutin, eriodictyol) treatment enhanced leaf area, root length, and plant height under salt and alkali stress treatments. These results suggest that G. soja mitigates ion toxicity via root Na⁺ sequestration, stress-responsive gene regulation, and flavonoid-mediated growth enhancement, providing insights into adaptive mechanisms under salt and alkali stress.

Soil salinization poses a major constraint to global agriculture. Apocynum venetum, a salt-tolerant halophyte, provides an effective model for investigating salt-adaptive strategies; however, the temporal dynamics of its tolerance-associated genes and metabolites remain unclear. In this study, integrated transcriptomics, metabolomics (UHPLC-MS), physiological assays, and weighted gene co-expression network analysis (WGCNA) were conducted to characterize early (7-day) and late (18-day) responses to 200 mM NaCl stress. NaCl stress significantly reduced chlorophyll content while increasing Na⁺ accumulation, MDA levels, antioxidant enzyme activities (SOD and CAT), and total flavonoid content. Early responses (NaCl7) were marked by accumulation of ferulic acid, rhamnetin, and 3,4-dihydrocoumarin, with activation of plant hormone (ABA, auxin, zeatin) and MAPK signaling pathways. Late responses (NaCl18) exhibited increased accumulation of scopoletin, formononetin, and caffeyl-alcohol, with enrichment of phenylpropanoid biosynthesis, glutathione metabolism, and photosynthesis-related pathways. WGCNA identified early-response hub genes, including AOC, MAPKKK17/18, CYP98A, and CCoAOMT, coordinating stress signaling and antioxidant metabolism. Late stress responses involved genes like CPK, GST, CYCD3, and ARF, modulating calcium signaling and ROS detoxification. Genes shared across phases included CYP90C1, HD-ZIP, HSP20, and PP2C, regulating protein stabilization and stress signaling. These findings reveal a two-phase salt tolerance strategy in A. venetum, integrating early signaling and late metabolic adaptation.