Genetius

Using Rhizophagus irregularis to connect two Medicago truncatula plants, the study shows that intact common mycelial networks (CMNs) transmit signals from wounded or flg22‑treated sender plants that reprogram the receiver's leaf transcriptome and metabolome, leading to altered isoprenoid production. These CMN‑mediated signals enhance resistance to Fusarium sporotrichoides while increasing susceptibility to Botrytis cinerea, indicating pathogen‑specific effects of neighbour‑primed defences.

The study examined how interactions among plant genotype, aphid genotype, and rhizobial symbiosis affect defense priming in two Medicago truncatula genotypes inoculated with Sinorhizobium meliloti or supplied with nitrate. Aphid performance, plant fitness, and leaf expression of jasmonic acid and salicylic acid pathway genes were monitored over 12 days, revealing that both plant and aphid genotypes and rhizobial inoculation jointly shape defense outcomes. The results highlight the importance of genetic context and microbial symbiosis in multitrophic interactions and suggest avenues for enhancing pest resistance via beneficial microbes.

The study identifies MtFTb1 and MtFTb2 as essential, redundant regulators of long‑day flowering in the legume Medicago truncatula, demonstrating that they are required for up‑regulating MtFTa1 under vernalised long‑day conditions. Using CRISPR/Cas9‑generated single and double mutants, the authors show that double mutants are specifically delayed in flowering under long days while retaining vernalization responsiveness, and transcriptomic analyses reveal that MtFTb1/2 activate MADS‑box genes and other flowering regulators.

A yeast two‑hybrid screen using Medicago truncatula root cDNA identified MtCSP1, a BTB/POZ domain protein, as an interactor of the ARF GTPase MtARFA1. Interaction was confirmed in planta by co‑immunopurification and bimolecular fluorescence complementation, showing localization to late‑endosomal vesicles, and functional assays in transgenic roots demonstrated that MtCSP1 is essential for rhizobial infection progression and nodule organogenesis, linking small GTPase activity to ubiquitin‑mediated protein turnover during symbiosis.

Using a simple root immersion system, the study examined how NRT2.1 and NRT1.1A/B transporters influence external and apoplastic pH during nitrate uptake in Medicago truncatula mutants. Loss of NRT2.1 blocked nitrate‑induced media alkalization, while NRT1.1A/B mutants showed a transient reduction, and HPTS imaging revealed that apoplastic pH initially drops in a NRT1.1‑dependent manner, suggesting cell‑wall buffering and H⁺‑ATPase activity decouple media and apoplastic pH changes.

The study reveals that the cold‑repressed transcription factor MtCBF4 suppresses anthocyanin synthesis in Medicago truncatula by repressing MtLAP1 and modulating histone H3K27 trimethylation via activation of the demethylase MtJMJ13. MtJMJ13, in turn, demethylates the gene bodies of MtCBF4 and other negative regulators, creating a feedback loop that is inhibited under cold stress, thereby increasing anthocyanin accumulation and enhancing cold tolerance. This work identifies a transcription‑epigenetic regulatory module controlling anthocyanin production during cold stress.

The study combines mathematical modeling, live-cell fluorescence imaging, and bacterial mutant analyses to investigate how Sinorhizobium meliloti moves within infection threads of Medicago truncatula root hairs, finding that movement is slow and likely passive, relying on flagella-independent surface translocation mediated by the rhizobactin 1021 surfactant. Flagella-deficient mutants retain colonization ability, whereas disruption of rhbE impairs surface motility, leads to branched infection threads, and compromises nodule development.

The study identifies Medicago truncatula mutants in the immune kinase SOBIR1 and examines their effects on symbiotic interactions. While SOBIR1 mutants form normal nodules with Sinorhizobium meliloti, they develop fewer and abnormal nodules with S. medicae, and they show increased colonization by the arbuscular mycorrhizal fungus Glomus versiforme, with SOBIR1 localized to the periarbuscular membrane. These findings indicate that SOBIR1 modulates both bacterial nodulation and fungal mycorrhizal symbioses, but with opposite outcomes upon mutation.

The authors created a Medicago truncatula–Diversispora epigaea yeast‑two‑hybrid (Y2H) library and a vector system for bimolecular fluorescence complementation (BiFC) in mycorrhizal roots, enabling rank‑ordered identification of protein‑protein interactions during arbuscular mycorrhizal (AM) symbiosis. Using these tools, they screened for interactors of the essential kinase CKL2 and found three 14‑3‑3 proteins as top candidates, confirming a CKL2:14‑3‑3 interaction at the periarbuscular membrane and suggesting a signaling role. The resources provide a platform for rapid functional analysis of AM‑related proteins.

The authors present an optimized protocol for applying the Xenium in situ sequencing platform to FFPE sections of plant tissues, specifically Medicago truncatula roots and nodules, overcoming challenges such as cell wall autofluorescence and probe accessibility. The workflow includes customized tissue preparation, probe design with reduced autofluorescence, and modular gene panels (380‑gene core and 100‑gene add‑on), enabling high‑resolution spatial transcriptomics across nodule developmental stages and facilitating downstream functional validation.