A Transcriptome Profile Reveals The Regulatory Mechanism of Verticillium Dahliae Against Bacillus

Abstract

Background: Verticillium dahliae, the causal agent of Verticillium wilt, is notoriously invasive in many crops and has been involved in numerous epidemics worldwide. Bacillus species, as representatives of biocontrol bacteria, produce a variety of lipopeptides (LPs), which are useful as biofungicides to many pathogenic fungi, including Verticillium dahliae. This study will explore the mechanism of resistance of V. dahliae to Bacillus and biocontrol bacteria.Results: By using in vitro confrontation bioassays, we found that under the stress induced by Bacillus, the spore vitality of V. dahliae with larger colonies was higher, and more abundant microsclerotia were formed. Then, according to the RNA-Seq analysis, the target of rapamycin (TOR) and mitophagy pathways were enriched among the significantly upregulated 542 genes observed in two co-culture groups with different colony sizes. In addition, in the group of V. dahliae with large colonies, the pathways related to cell wall synthesis, microsclerotia formation and the clearance of reactive oxygen species were regulated, and the expression of genes was up-regulated.Conclusion: This study found that the larger colonies of V. dahliae were more resistant to the antagonistic actions of Bacillus and the likelihood of the formation of homeostasis. Therefore, the prevention of Verticillium wilt by Bacillus is more effective than the treatment of an active fungal infection. These transcriptomic insights provide direction for the use of fungicides in the prevention and treatment of diseases such as Verticillium wilt.

Response of Fusarium pseudograminearum to Biocontrol Agent Bacillus velezensis YB-185 by Phenotypic and Transcriptome Analysis

“…Thus far, there are several transcriptome studies of plant pathogenic fungi incubated with Bacillus species or their crude culture filtrates. For example, RNA was analyzed from Colletotrichum gloeosporioides TS-09 grown on PDA with B. amyloliquefaciens SDF-005 for 9 days [ 39 ], Verticillium dahliae VdSHZ-9 grown on PDA with Bacillus N-4 for 7 days [ 40 ], and Fusarium oxysporum grown on PDA with B. subtilis HSY21 for 2 and 3 days [ 29 ]. RNA was also analyzed for Sclerotinia sclerotiorum 1980 grown on PDA containing 10% culture filtrate of B. amyloliquefaciens Bam22 for 1 day [ 41 ], and Botrytis cinerea strain B05.10 grown in PDB with B. subtilis MBI 600 culture filtrate for 0, 24, 48, and 72 h [ 42 ].…”

“…There was down-regulation of one 1,3-beta-glucan synthase and three 1,3-beta-glucanosyltransferase genes at 4 and 16 h. Note that 1,3-Beta-glucan synthase is a glucosyltransferase that generates beta-glucan, a major component of fungal cell walls, and 1,3-beta-glucanosyltransferase is involved in the elongation of 1,3-beta-glucan [ 43 ]. For both S. sclerotiorum and V. dahilae with Bacillus , 1,3-beta-glucan synthase DEGs were up-regulated [ 40 , 41 ]. It was concluded that this was an attempt to alleviate cell wall damage.…”

“…Chitin synthase is a glycosyltransferase that catalyzes formation of chitin, another major component of fungal cell walls [ 44 ]. Tian et al [ 40 ] reported that DEGs related to chitin synthase in V. dahilae were up-regulated by Bacillus . Overall, there may be more limited new cell wall synthesis of F. pseudograminearum with Bacillus stress limited to earlier in the interaction.…”

“…Mechanosensitive ion channels provide protection against hypoosmotic shock, responding to membrane tension, and reduced levels of them could result in membrane fragility and loosening [ 47 ]. However, other transcriptome studies of plant pathogenic fungi with Bacillus did not report DEGs related to mechanosensitive ion channels [ 29 , 39 , 40 , 41 , 42 ].…”

“…Peroxiredoxins are cysteine-dependent peroxidases that limit peroxide levels within cells [ 49 ], and thioredoxins reduce oxidized cysteine residues cleaving disulfide bonds, protecting proteins from oxidative aggregation and inactivation [ 50 ]. With Bacillus or culture filtrate, however, S. sclerotiorum up-regulated peroxidase and catalase DEGs [ 41 ], and V. dahilae up-regulated SOD, catalase, peroxiredoxin, and thioredoxin DEGs [ 40 ]. This was proposed to be part of an ROS stress response.…”