Jasmonates (JAs) are the most effective inducers for the biosynthesis of various secondary metabolites. Currently, jasmonate ZIM domain (JAZ) and its interactors, such as MYC2, constitute the main JA signal transduction cascade, and such a cascade fails to directly regulate all the taxol biosynthesis genes, especially the rate-limit gene, DBAT. Another JA signaling branch, JAV and WRKY, would probably fill the gap. Here, TcJAV3 was the closest VQ-motif-containing protein in Taxus chinensis to AtJAV1. Although TcJAV3 was overexpressed in AtJAV1 knockdown mutant, JAVRi17, the enhanced disease resistance to Botrytis cinerea caused by silencing AtJAV1 was completely recovered. The results indicated that TcJAV3 indeed transduced JA signal as AtJAV1. Subsequently, TcWRKY26 was screened out to physically interact with TcJAV3 by using a yeast two-hybrid system. Furthermore, bimolecular fluorescence complementation and luciferase complementary imaging also confirmed that TcJAV3 and TcWRKY26 could form a protein complex in vivo. Our previous reports showed that transient TcWRKY26 overexpression could remarkably increase DBAT expression. Yeast one-hybrid and luciferase activity assays revealed that TcWRKY26 could directly bind with the w_a-box of the DBAT promoter to activate downstream reporter genes. All of these results indicated that TcWRKY26 acts as a direct regulator of DBAT, and the TcJAV3–TcWRKY26 complex is actually another JA signal transduction mode that effectively regulates taxol biosynthesis in Taxus. Our results revealed that JAV–WRKY complexes directly regulated DBAT gene in response to JA stimuli, providing a novel model for JA-regulated secondary metabolism. Moreover, JAV could also transduce JA signal and function non-redundantly with JAZ during the regulation of secondary metabolisms.

The majority of terrestrial plants can interact with arbuscular mycorrhizal fungi (AMF) to form symbiotic relationships. AMF colonization not only enhances the host plant’s uptake of mineral nutrients but also improves its tolerance to biotic and abiotic stresses. In return, the host plant supplies the AMF with carbon sources essential for completing its life cycle. How AMF overcome the plant immune system to successfully establish symbiosis has remained an unresolved question. During colonization, AMF also secrete effector proteins, similar to how pathogenic fungi utilize effectors to promote virulence. In this study, we employed machine learning models such as SignalP 6.0 and EffectorP 3.0 to predict potential effectors in Rhizophagus irregularis, leading to the identification of 227 effector candidates. Using EffectorP 3.0, ApoplastP, and LOCALIZER, most R. irregularis effectors were predicted to be localized in the cytoplasm rather than the apoplast, suggesting a functional role in regulating symbiotic development. Only 26% of the predicted effectors were annotated by Pfam, indicating that the majority are proteins of unknown function. Effector proteins from 14 microbial species representing five ecological types (Ectomycorrhizae, Ericoid mycorrhizae, Endophyte, Arbuscular mycorrhizae, and Pathogen) clustered distinctly by species, highlighting the high degree of species specificity among effectors. Two R. irregularis effectors containing the RxLR motif were identified. Although these effectors localized to the cytoplasm, they did not exhibit virulence factor activity. Additionally, we characterized a functionally conserved chitin deacetylase effector, RiPDA1, which localized to the apoplastic space. The Y2H assay indicated that RiPDA1 forms homodimers. The in vitro chitin-binding assay showed that RiPDA1 has an affinity for chitin. RiPDA1 may function as a secretory polysaccharide deacetylase that facilitates symbiosis by deacetylating chitin oligomers. In summary, this study systematically identified and characterized effector proteins in R. irregularis. Similar to pathogenic fungi, AMF appear to employ cell wall-modifying enzymes to overcome plant immune defenses.

Perennial ryegrass is a widely cultivated cool-season forage and turf grass species whose growth and development are limited by drought and high temperature. MAX2 is an F-box leucine-rich repeat (LRR) protein, which serves as a central component of strigolactone (SL) and karrikin (KAR) signaling pathways, involved in multiple growth and developmental processes as well as stress response. Here, we identified LpMAX2, a perennial ryegrass (Lolium perenne L.) homolog of Arabidopsis MAX2 (AtMAX2) and rice D3. LpMAX2 can interact with AtD14 and LpD14 in an SL-dependent manner, implying functional conservation with AtMAX2. Overexpression of LpMAX2 in the Arabidopsis max2-3 mutant partially rescued leaf morphology, hypocotyl elongation, and branching phenotypes, while fully restoring drought tolerance, highlighting the evolutionarily conserved roles of MAX2 in plant growth and drought resistance. In conclusion, LpMAX2 is evolutionarily conserved in SL/KAR signaling pathways, highlighting its potential function in drought adaptation. In addition to elucidating the biological function of LpMAX2, this study identifies a promising genetic target for enhancing stress resilience in forage grasses through biotechnological approaches.

Karrikin (KAR) signaling plays crucial roles in plant development, regulating key traits such as photomorphogenesis, root hair development, and arbuscular mycorrhizal symbiosis. SUPPRESSOR OF MAX2 1 (SMAX1), a key negative regulator of the KAR pathway, has been functionally studied in several plant species. However, the SMAX1 protein remains poorly understood in Medicago truncatula, an important model legume, which limits the comprehensive understanding and application of the KAR pathway in legumes. In this study, we identified the single SMAX1 ortholog MtSMAX1 in M. truncatula. Sequence alignment and structural modeling analyses revealed that MtSMAX1 is highly conserved with SMAX1 homologs from other plant species. Yeast two-hybrid assays demonstrated that MtSMAX1 interacts with two KAR signaling receptors KARRIKIN INSENSITIVE 2 (MtKAI2a/b). In addition, both MtKAI2a/b interact with the F-box protein MORE AXILLARY GROWTH 2 (MtMAX2), suggesting a conserved KAR signaling pathway in M. truncatula. To further investigate the biological functions of MtSMAX1, we generated two distinct CRISPR-edited mutant lines. The loss-of-function mutant Mtsmax1, which carries a premature termination mutation, displays defective phenotypes including reduced seed size, dwarfism, and delayed flowering. In contrast, the Mtsmax1^ΔQ210 mutant, harboring a single glutamine deletion at position 210, exhibits specific defects only in seed development. These phenotypic differences indicate a previously unreported role of MtSMAX1 in regulating legume seed development, with the conserved Q210 residue potentially involved in this process. Furthermore, MtSMAX1 overexpression lines exhibit phenotypes opposite to those of the mutants, further validating the biological functions of MtSMAX1. Gene expression analysis of key developmental marker genes revealed altered expression levels in MtSMAX1 mutants, which are tightly consistent with the corresponding phenotypic variations. These results suggest that MtSMAX1 likely functions as an important transcriptional regulator to modulate the expression of downstream developmental genes. Collectively, our findings establish MtSMAX1 as a pivotal regulator of multiple developmental processes in legumes and provide a foundation for elucidating the broader biological functions and regulatory mechanisms of the KAR signaling pathway.

Plant hormones and their synthetic analogueues offer sustainable alternatives for crop protection, yet the direct antifungal activity of strigolactone (SL) and its analogues against necrotrophic pathogens remain largely unexplored. Here, we screened eight phytohormones and related analogues for treatments of Botrytis cinerea and identified the SL analogue rac-GR24 (racemic GR24) as a concentration-dependent growth inhibitor active at low micromolar concentrations. Given the stereochemical complexity of SLs and their analogues, we evaluated multiple enantiopure isomers and found that ent-5DS and GR24^ent-5DS, which differ in configuration from natural SLs, exhibited the strongest inhibitory activity. This stereospecific response was further validated using another filamentous fungus, Sclerotinia sclerotiorum, which displayed an identical susceptibility profile. Combinatorial treatments with enantiopure isomers and double-concentration rac-GR24 revealed that the antifungal effect of the racemate is primarily attributable to the GR24^ent-5DS enantiomer, whereas the opposite enantiomer GR24^5DS is almost inactive. Collectively, our findings uncover a stereospecific response in fungal pathogens, demonstrating that B. cinerea and S. sclerotiorum respond to exogenous SL analogues in a chirally selective manner. This work establishes a stereochemically defined framework for developing enantioselective fungicidal agents with potential applications in sustainable agriculture.