Fusarium wilt of banana, caused by Fusarium oxysporum f. sp. cubense (Foc), is a destructive vascular disease that seriously threatens global banana production. To investigate the contribution of histidine metabolism to Foc growth and pathogenicity, we functionally characterized FoHis2, a putative histidinol-phosphate phosphatase in Foc race 4 (Foc4). Targeted deletion of FoHis2 severely compromised histidine prototrophy, with the ΔFoHis2 mutant growing slowly on potato dextrose agar and even more slowly on minimal medium (MM, no histidine added). Exogenous histidine fully restored the mutant growth to wild-type (WT) levels, whereas histidinol supplementation rescued the colony size but not the reduced aerial mycelium formation. The ΔFoHis2 mutant exhibited markedly reduced vegetative growth and hyphal branching, and increased sensitivity to elevated H₂O₂ concentrations, compared with the WT strain. Consistent with the oxidative stress phenotype, peroxisome-associated genes were down-regulated in the ΔFoHis2 mutant. FoHis2 was dispensable for conidiation, cell wall integrity, and fusaric acid and beauvericin biosynthesis. Pathogenicity assays showed that the deletion of FoHis2 severely compromised cellophane penetration and greatly reduced disease incidence and severity on Cavendish banana plantlets, whereas genetic complementation restored the WT phenotypes. These results indicate that FoHis2-mediated histidine biosynthesis is essential for metabolic homeostasis, stress adaptation, and full virulence in Foc4, and highlight histidine metabolism as a potential target for controlling Fusarium wilt in banana.

As a non-pathogenic oomycete, Pythium oligandrum possesses unique advantages, particularly in the context of being a biological control agent. With the increasing awareness of consumer consciousness, people are paying more attention to the use of environmentally friendly strategies in plant disease prevention and control. Pythium oligandrum is a type of biocontrol oomycete that can be developed as a biological control agent, and it does not have adverse effects on humans in the prevention and control of plant diseases. Consequently, there is increasing scientific interest in the beneficial plant–microbe interactions mediated by P. oligandrum. Currently, the main points of focus regarding the beneficial role of P. oligandrum in plant interactions are as follows: (i) P. oligandrum can activate plant defense responses and cause plants to produce resistance, thus protecting them from disease attacks; (ii) it is a strong mycoparasite that can coil around various oomycetes and fungi, directly killing pathogenic microorganisms; (iii) in addition, it can also promote plant growth. In this paper, we will discuss the aforementioned three main features in detail.

Potato production is severely threatened by the oomycete Phytophthora infestans, the fungus Alternaria solani, and the bacterium Ralstonia solanacearum; however, strategies capable of simultaneously managing these three pathogen classes remain relatively scarce. In this study, we designed a series of signal peptide (SP)-fused recombinant constructs containing four functional modules with distinct antimicrobial and immune-inducing properties: GAFP1-2×FYVE, an oomycete-inhibiting antimicrobial protein; BbAFP1-ErBD, a fungal-suppressive protein fragment; the pathogen-associated molecular pattern (PAMP) csp22 derived from R. solanacearum, which elicits effective anti-bacterial immunity; and the microbe-associated molecular pattern (MAMP) PpEli2 identified from Pythium periplocum, which triggers broad-spectrum plant defense responses. Through systematic evaluation of six module order rearrangements, we identified SP-cBG as the optimal multi-domain combination. Further optimization via the introduction of a rigid alpha-helical linker (HL4) yielded SP-cBG-HL4, which tended to show superior resistance against all three pathogens, as reflected in smaller lesion diameters and decreased bacterial titers. qRT-PCR analyses revealed that SP-cBG-HL4 significantly upregulated PTI (CYP71D20, PTI5), SA (PR1, PR2), and JA/ET (PR3, PR4) defense marker genes. Collectively, these findings show that modular domain assembly combined with linker-mediated modular combinatorial optimization represents a powerful engineering strategy for achieving broad-spectrum disease resistance, offering a promising approach to simultaneously control oomycete, fungal, and bacterial pathogens of plants.