Biological control of Magnaporthe oryzae using natively isolated Bacillus subtilis G5 from Oryza officinalis roots.

Rice blast, caused by Magnaporthe oryzae, is a major threat to global rice production causing significant crop losses and impacting grain quality. The annual loss of rice production due to this disease ranges from 10% to 30%. The use of biologically controlled strains, instead of chemical pesticides, to control plant diseases has become a research hotspot. In this study, an antagonistic endophytic bacterial strain was isolated from the roots of Oryza officinalis using the traditional isolation and culture methods. A phylogenetic tree based on 16S RNA and whole-genome sequencing identified isolate G5 as a strain of Bacillus subtilis. This isolate displayed strong antagonistic effects against different physiological strains of M. oryzae. After co-culture in LB medium for 7 days, the inhibition rates of the mycelial growth of four strains of M. oryzae, ZB15, WH97, Guy11, and T-39800E were 98.07 ± 0.0034%, 98.59 ± 0.0051%, 99.16 ± 0.0012%, and 98.69 ± 0.0065%, respectively. Isolate G5 significantly inhibited the formation of conidia of M. oryzae, with an inhibition rate of 97% at an OD600 of 2. Isolate G5 was able to provide 66.81% protection against rice blast under potted conditions. Whole-genome sequencing revealed that the genome size of isolate G5 was 4,065,878 bp, including 4,182 coding genes. Using the anti-SMASH software, 14 secondary metabolite synthesis gene clusters were predicted to encode antifungal substances, such as fengycin, surfactin, and bacilysin. The G5 isolate also contained genes related to plant growth promotion. These findings provide a theoretical basis for expounding the biocontrol mechanisms of this strain and suggest further development of biogenic agents that could effectively inhibit rice blast pathogen growth and reduce crop damage, while being environmentally friendly, conducive to ecological development, and a sustainable alternative to chemical pesticides. This study also enriches the relevant research on endophytes of wild rice, which proves that wild rice is a valuable microbial resource bank.

Transcriptome analysis confers a complex disease resistance network in wild rice Oryza meyeriana against Xanthomonas oryzae pv. oryzae.

Rice bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the devastating diseases of rice. It is well established that the wild rice Oryza meyeriana is immune to BB. In this study, the transcriptomic analysis was carried out by RNA sequencing of O. meyeriana leaves, inoculated with Xoo to understand the transcriptional responses and interaction between the host and pathogen. Totally, 57,313 unitranscripts were de novo assembled from 58.7 Gb clean reads and 14,143 unitranscripts were identified after Xoo inoculation. The significant metabolic pathways related to the disease resistance enriched by KEGG, were revealed to plant-pathogen interaction, phytohormone signaling, ubiquitin mediated proteolysis, and phenylpropanoid biosynthesis. Further, many disease resistance genes were also identified to be differentially expressed in response to Xoo infection. Conclusively, the present study indicated that the induced innate immunity comprise the basal defence frontier of O. meyeriana against Xoo infection. And then, the resistance genes are activated. Simultaneously, the other signaling transduction pathways like phytohormones and ubiquitin mediated proteolysis may contribute to the disease defence through modulation of the disease-related genes or pathways. This could be an useful information for further investigating the molecular mechanism associated with disease resistance in O. meyeriana.

C1 metabolism and the Calvin cycle function simultaneously and independently during HCHO metabolism and detoxification in Arabidopsis thaliana treated with HCHO solutions.

Formaldehyde (HCHO) is suggested to be detoxified through one-carbon (C1) metabolism or assimilated by the Calvin cycle in plants. To further understand the function of the Calvin cycle and C1 metabolism in HCHO metabolism in plants, HCHO elimination and metabolism by Arabidopsis thaliana in HCHO solutions was investigated in this study. Results verified that Arabidopsis could completely eliminate aqueous HCHO from the HCHO solutions. Carbon-13 nuclear magnetic resonance ((13)C-NMR) analysis showed that H(13)CHO absorbed by Arabidopsis was first oxidized to H(13)COOH. Subsequently, a clear increase in [U-(13)C]Gluc peaks accompanied by a strong enhancement in peaks of [2-(13)C]Ser and [3-(13)C]Ser appeared in Arabidopsis. Pretreatment with cyclosporin A or L-carnitine, which might inhibit the transport of (13)C-enriched compounds into chloroplasts and mitochondria, caused a remarkable decline in yields of both [U-(13)C]Gluc and [3-(13)C]Ser in H(13)CHO-treated Arabidopsis. These results suggested that both the Calvin cycle and the C1 metabolism functioned simultaneously during HCHO detoxification. Moreover, both functioned more quickly under high H(13)CHO stress than low H(13)CHO stress. When a photorespiration mutant was treated in 6 mm H(13)CHO solution, formation of [U-(13)C]Gluc and [2-(13)C]Ser was completely inhibited, but generation of [3-(13)C]Ser was not significantly affected. This evidence suggested that the Calvin cycle and C1 metabolism functioned independently in Arabidopsis during HCHO metabolism.