Maize Root Exudates Recruit Bacillus amyloliquefaciens OR2-30 to Inhibit Fusarium graminearum Infection

Abstract

Bacillus spp. can exert plant growth-promoting effects and biocontrol effects after effective colonization, and bacterial chemotaxis toward plant root exudates is the initial step to colonize. Under biotic stress, plants are able to alter their root exudates in order to attract or avoid different types of microbes. Hence, Bacillus chemotaxis toward root exudates after pathogen infection is crucial for exerting their beneficial effects. In this study, B. amyloliquefaciens OR2-30 strain, which exhibited greater chemotaxis ability toward maize root exudates after Fusarium graminearum infection, was screened from 156 rhizosphere microorganisms. The infected maize root exudates were further confirmed to improve the swarming and biofilm formation ability of OR2-30 strain. Chemotaxis, swarming and biofilm formation ability were able to influence bacterial colonization. Indeed, the OR2-30 strain displayed more effective colonization ability in maize rhizosphere after F. graminearum inoculation. Moreover, lipopeptides produced by OR2-30 were identified as iturins and responsible for suppressing F. graminearum growth. Further study showed that lipopeptides suppressed the growth of F. graminearum by inhibiting conidia formation and germination, inducing reactive oxygen species (ROS) production and causing cell death in mycelium. Eventually, OR2-30 strain increased maize resistance against F. graminearum. These results suggested that maize root exudates could recruit B. amyloliquefacines OR2-30 after F. graminearum infection, OR2-30 then suppress the F. graminearum by producing lipopeptides, such as iturins, to protect maize.

degQ associated with the degS/degU two‐component system regulates biofilm formation, antimicrobial metabolite production, and biocontrol activity in Bacillus velezensis DMW1

“…The lipopeptides iturin and fengycin exhibit strong antagonistic effects against F. graminearum and are the major antifungal substances produced by Bacillus spp. (Hanif et al, 2019 ; Xie et al, 2022 ). Our HPLC results showed that the deletion of degQ and degU significantly reduced iturin and fengycin yields based on the calculation of peak areas, which corroborate our predictions (Figure 5c,d ).…”

Broad‐spectrum antagonistic potential of Bacillus spp. volatiles against Rhizoctonia solani and Xanthomonas oryzae pv. oryzae

“…The expression profile of the rice plant defence genes ( LOX1, EXP18, GluA, PAL1, PBZ1, SOD1, PR‐3 , and PR‐4 ) was analyzed after exposure to synthetic VOCs in the pot experiment (Xie et al 2022). The leaf samples were collected after 7 days of exposure to the selected VOCs.…”

Effects of interaction of Epichloë gansuensis and Bacillus strains on the seed germination and seedling growth in Achnatherum inebrians plants

“…(2021) demonstrated that Bacillus X13, Bacillus X14, and co-inoculation of both strains exhibited a promotion effect on total dry biomass, crude protein content and digestibility in Megathyrsus maximus under drought. According to Xie et al (2022), maize root exudate recruited B. amyloliquefaciens OR2-30 to colonize the rhizosphere and then inhibited the growth of Fusarium graminearum by producing iturins. In our experiments, some Bacillus strains increased the growth of A. inebrians at the seedling emergence (21 days old) and mature stage (grown in the 2:1 vermiculite and black soil mixture for 3 months).…”