Comparative Transcriptome Analysis Unravels the Response Mechanisms of Fusarium oxysporum f.sp. cubense to a Biocontrol Agent, Pseudomonas aeruginosa Gxun-2.

Banana Fusarium wilt, which is caused by Fusarium oxysporum f.sp. cubense Tropical Race 4 (FOC TR4), is one of the most serious fungal diseases in the banana-producing regions in east Asia. Pseudomonas aeruginosa Gxun-2 could significantly inhibit the growth of FOC TR4. Strain Gxun-2 strongly inhibited the mycelial growth of FOC TR4 on dual culture plates and caused hyphal wrinkles, ruptures, and deformities on in vitro cultures. Banana seedlings under pot experiment treatment with Gxun-2 in a greenhouse resulted in an 84.21% reduction in the disease. Comparative transcriptome analysis was applied to reveal the response and resistance of FOC TR4 to Gxun-2 stress. The RNA-seq analysis of FOC TR4 during dual-culture with P. aeruginosa Gxun-2 revealed 3075 differentially expressed genes (DEGs) compared with the control. Among the genes, 1158 genes were up-regulated, and 1917 genes were down-regulated. Further analysis of gene function and the pathway of DEGs revealed that genes related to the cell membrane, cell wall formation, peroxidase, ABC transporter, and autophagy were up-regulated, while down-regulated DEGs were enriched in the sphingolipid metabolism and chitinase. These results indicated that FOC TR4 upregulates a large number of genes in order to maintain cell functions. The results of qRT-PCR conducted on a subset of 13 genes were consistent with the results of RNA-seq data. Thus, this study serves as a valuable resource regarding the mechanisms of fungal pathogen resistance to biocontrol agents.

A Comparative Transcriptome Analysis Unveils the Mechanisms of Response in Feather Degradation by Pseudomonas aeruginosa Gxun-7.

Microbial degradation of feathers offers potential for bioremediation, yet the microbial response mechanisms warrant additional investigation. In prior work, Pseudomonas aeruginosa Gxun-7, which demonstrated robust degradation of feathers at elevated concentrations, was isolated. However, the molecular mechanism of this degradation remains only partially understood. To investigate this, we used RNA sequencing (RNA-seq) to examine the genes that were expressed differentially in P. aeruginosa Gxun-7 when exposed to 25 g/L of feather substrate. The RNA-seq analysis identified 5571 differentially expressed genes; of these, 795 were upregulated and 603 were downregulated. Upregulated genes primarily participated in proteolysis, amino acid, and pyruvate metabolism. Genes encoding proteases, as well as those involved in sulfur metabolism, phenazine synthesis, and type VI secretion systems, were notably elevated, highlighting their crucial function in feather decomposition. Integration of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) taxonomies, combined with a review of the literature, led us to propose that metabolic feather degradation involves environmental activation, reducing agent secretion, protease release, peptide/amino acid uptake, and metabolic processes. Sulfite has emerged as a critical activator of keratinase catalysis, while cysteine serves as a regulatory mediator. qRT-PCR assay results for 11 selected gene subset corroborated the RNA-seq findings. This study enhances our understanding of the transcriptomic responses of P. aeruginosa Gxun-7 to feather degradation and offers insights into potential degradation mechanisms, thereby aiding in the formulation of effective feather waste management strategies in poultry farming.

Comparative Transcriptome Analysis Reveals the Molecular Mechanisms of Acetic Acid Reduction by Adding NaHSO3 in Actinobacillus succinogenes GXAS137.

Acetic acid (AC) is a major by-product from fermentation processes for producing succinic acid (SA) using Actinobacillus succinogenes. Previous experiments have demonstrated that sodium bisulfate (NaHSO3) can significantly decrease AC production by A. succinogenes GXAS137 during SA fermentation. However, the mechanism of AC reduction is poorly understood. In this study, the transcriptional profiles of the strain were compared through Illumina RNA-seq to identify differentially expressed genes (DEGs). A total of 210 DEGs were identified by expression analysis: 83 and 127 genes up-regulated and down-regulated, respectively, in response to NaHSO3 treatment. The functional annotation analysis of DEGs showed that the genes were mainly involved in carbohydrates, inorganic ions, amino acid transport, metabolism, and energy production and conversion. The mechanisms of AC reduction might be related to two aspects: (i) the lipoic acid synthesis pathway (LipA, LipB) was significantly down-regulated, which blocked the pathway catalyzed by pyruvate dehydrogenase complex to synthesize acetyl-coenzyme A (acetyl-CoA) from pyruvate; (ii) the expression level of the gene encoding bifunctional acetaldehyde-alcohol dehydrogenase was significantly up-regulated, and this effect facilitated the synthesis of ethanol from acetyl-CoA. However, the reaction of NaHSO3 with the intermediate metabolite acetaldehyde blocked the production of ethanol and consumed acetyl-CoA, thereby decreasing AC production. Thus, our study provides new insights into the molecular mechanism of AC decreased underlying the treatment of NaHSO3 and will deepen the understanding of the complex regulatory mechanisms of A. succinogenes.