Fungal diseases affecting maize not only reduce maize yields but also generate fungal toxins that pose risks to both human and animal health, particularly when the straw is returned to the field. Microbial in-situ control is considered an environmentally friendly method that effectively addresses the limitations of unstable effects. In this study, we isolated Bacillus velezensis zm026 from rhizosphere soil for in-situ restoration, based on the soil community structure, which exhibits high antagonistic activity against Fusarium verticillioides and Exserohilum turcicum. Zm026 effectively colonized the surface of maize roots within 5 days and activated the plant immune system, significantly increasing the expression of defense genes such as ZmGST, ZmZHD, ZmPR-1, ZmPR-2, and ZmPR-3. The efficient anti-fungal substance of zm026 was identified by HPLC-MS and determined to be bacillomycin D. Further observations using trypan blue staining, along with DAPI (4´,6-diamidino-2-phenylindole) and PI (propidium iodide) fluorescent staining, revealed that bacillomycin D could inhibit fungal spore germination, disrupt the integrity of fungal cell membranes, induce apoptosis, and cause spore tips to protrude, swell, or rupture. Ultimately, indoor pot experiments demonstrated that the application of zm026 fermentation broth significantly promoted growth, inhibited the onset of fungal diseases in maize, and effectively reduced the abundance of Fusarium spp. in maize grains. This research provides a beneficial in-situ restoration strain for the high-quality development of maize.

LysM proteins contain the lysin domain (LysM), bind chitin and are found in various organisms including fungi. In phytopathogenic fungi, certain LysM proteins act as effectors to inhibit host immunity, thus increasing fungal virulence. However, our understanding of the LysM protein family in Setosphaeria turcica is limited. In this study, eight StLysM genes are identified and designated as StLysM1 to StLysM8. The analysis of sequence features indicates that five proteins (StLysM1, StLysM2, StLysM5, StLysM6, and StLysM7) are potential effectors. Phylogenetic analysis suggests that the StLysMs are divided into fungal/bacterial and fungus-specific subclasses. Domain architecture analysis reveals that the five StLysM effectors exclusively harbor the LysM domain, whereas the other three StLysM proteins contain additional functional domains. Sequence conservation analysis shows that the fungal-specific LysM domain sequences share the ⁸GDxTC¹² and ²⁹WNP³¹ motifs as well as three highly conserved cysteine residues. Conversely, the LysM domain sequences from the bacterial/fungal branch have few conserved sites. Moreover, expression profiling analysis shows that the StLysM1 gene is significantly upregulated during the infection of maize. Yeast secretion assays and transient expression experiments demonstrate that StLysM1 is a secreted protein that can suppress BAX/INF1-induced programmed cell death in Nicotiana benthamiana. Further functional analysis suggests that StLysM1 cannot interact with itself but it can bind chitin. The transient expression of StLysM1 inhibits the chitin-triggered plant immune response, increasing susceptibility to the phytopathogenic fungus Botrytis cinerea in N. benthamiana. This study reveals that the S. turcica LySM protein family consists of eight members, highlighting the significance of StLysM1 as a vital effector in regulating plant immunity. The results provide insight into StLysMs and establish a foundation for understanding the roles of StLysM proteins in the pathogenic process of S. turcica.

The jasmonic acid (JA) signaling pathway is involved in plant growth, development, and response to abiotic or biotic stresses. MYC2, a bHLH transcription factor, is a regulatory hub in the pathway. The function of ZmMYC7, a putative MYC2 ortholog, in jasmonate-signaled defense responses of maize has not been reported. In this study, we found that ZmMYC7 possesses JID, TAD, bHLH and Zip domains and essential characteristics of transcription factors: a nuclear location and transactivation activity. The ZmMYC7 mutants showed markedly increased sensitivity to Fusarium graminearum and Setosphaeria turcica. The expression levels of the defense-associated genes ZmPR1, ZmPR2, ZmPR3, ZmPR5, ZmPR6, and ZmPR7 in response to F. graminearum infection were downregulated in ZmMYC7 mutants, while ZmPR4 and ZmPR10 were up-regulated. ZmMYC7 interacted with members of the ZmJAZ family, including ZmJAZ8, ZmJAZ11, and ZmJAZ12. ZmMYC7 physically interacted with G-box cis-elements in the ZmERF147 promoter in vitro and transcriptional activation of ZmERF147 by ZmMYC7 was inhibited by ZmJAZ11 and ZmJAZ12. ZmERF147 mutants were more susceptible to F. graminearum infection than inbred line B73 with concomitant down-regulation of all defense-associated ZmPRs except ZmPR4. These findings indicate that ZmMYC7 functions in maize resistance to F. graminearum and sheds light on maize defense responses to pathogenic fungi via the JA signaling pathway.