Mitigation of tobacco bacteria wilt with microbial degradation of phenolic allelochemicals

AMF inhibit the production of phenolic acid autotoxins at the seed-filling stage in soybeans with continuous monocropping

BACKGROUND

Soybean is the main oil crop in Northeast China. Continuous monocropping is more commonly used for soybean production due to rising market demand and arable land constraints. However, autotoxic substances, such as phenolic acids, produced by continuously cropped soybean can reduce yield and quality. The mycorrhiza formed of Arbuscular mycorrhizal fungi (AMF) and plant roots regulate the metabolic activities of the host plant and increase its disease resistance. The main purpose of this study was to inhibit the production of phenolic acids and determine the adverse effects on the growth of continuous monocropping soybean by inoculating Funneliformis mosseae (F. mosseae).

RESULTS

Transcriptomics results showed that the production of phenolic acids in continuous monocropping soybean roots was mainly regulated by the expression of the CHS6, PCL1, SAMT, SRG1, and ACO1 genes, and the expression of these genes was significantly downregulated after inoculation with F. mosseae. Metabolomics results showed that continuous monocropping soybean roots inoculated with F. mosseae inhibited phenolic acid production through the phenylpropane biosynthetic, α-linoleic acid, linoleic acid, and other metabolic pathways. Phenolic acids in the phenylpropane metabolic pathway, such as 4-hydroxybenzoic acid, phthalic acid, and vanillic acid, decreased significantly after inoculation with F. mosseae. The combined analysis of the two showed that genes such as YLS9 and ARF3 were positively correlated with 4-hydroxybenzoic acid and so on, while genes such as CHS6 and SRG1 were negatively correlated with butyric acid and so on.

CONCLUSION

F. mosseae regulated the expression of functional genes and related phenolic acid metabolic pathways produced by continuous monocropping soybean roots, inhibiting the production of phenolic acid autotoxic substances in continuous cropped soybean, and slowing down the disturbance of continuous monocropping. This study provides a new solution for continuous monocropping of plants to overcome the autotoxicity barrier and provides a new basis for the development and utilization of AMF as a biological agent.

How to deal with xenobiotic compounds through environment friendly approach?

Every year, a huge amount of lethal compounds, such as synthetic dyes, pesticides, pharmaceuticals, hydrocarbons, etc. are mass produced worldwide, which negatively affect soil, air, and water quality. At present, pesticides are used very frequently to meet the requirements of modernized agriculture. The Food and Agriculture Organization of the United Nations (FAO) estimates that food production will increase by 80% by 2050 to keep up with the growing population, consequently pesticides will continue to play a role in agriculture. However, improper handling of these highly persistent chemicals leads to pollution of the environment and accumulation in food chain. These effects necessitate the development of technologies to eliminate or degrade these pollutants. Degradation of these compounds by physical and chemical processes is expensive and usually results in secondary compounds with higher toxicity. The biological strategies proposed for the degradation of these compounds are both cost-effective and eco-friendly. Microbes play an imperative role in the degradation of xenobiotic compounds that have toxic effects on the environment. This review on the fate of xenobiotic compounds in the environment presents cutting-edge insights and novel contributions in different fields. Microbial community dynamics in water bodies, genetic modification for enhanced pesticide degradation and the use of fungi for pharmaceutical removal, white-rot fungi's versatile ligninolytic enzymes and biodegradation potential are highlighted. Here we emphasize the factors influencing bioremediation, such as microbial interactions and carbon catabolism repression, along with a nuanced view of challenges and limitations. Overall, this review provides a comprehensive perspective on the bioremediation strategies.

Pigmentiphaga kullae CHJ604 improved the growth of tobacco by degrading allelochemicals and xenobiotics in continuous cropping obstacles

Plant autotoxicity is considered to be one of the important causes of continuous cropping obstacles in modern agriculture, which accumulates a lot of allelochemicals and xenobiotics and is difficult to solve effectively. To overcome tobacco continuous obstacles, a strain Pigmentiphaga kullae CHJ604 isolated from the environment can effectively degrade these compounds in this study. CHJ604 strain can degrade 11 types of autotoxicity allelochemicals and xenobiotics (1646.22 μg/kg) accumulated in the soil of ten-years continuous cropping of tobacco. The 11 allelochemicals and xenobiotics significantly reduced Germination Percentage (GP), Germination Index (GI), and Mean Germination Time (MGT) of tobacco seeds, and inhibited the development of leaves, stems, and roots. These negative disturbances can be eliminated by CHJ604 strain. The degradation pathways of 11 allelochemicals and xenobiotics were obtained by whole genome sequence and annotation of CHJ604 strain. The heterologous expression of a terephthalate 1,2-dioxygenase can catalyze 4-hydroxybenzoic acid, 4-hydroxy-3-methoxybenzoic acid, 4-hydroxybenzaldehyde, and 4-hydroxy-3-methoxy-benzaldehyde, respectively. The phthalate 4,5-dioxygenase can catalyze phthalic acid, diisobutyl phthalate, and dibutyl phthalate. These two enzymes are conducive to the simultaneous degradation of multiple allelochemicals and xenobiotics by strain CHJ604. This study provides new insights into the biodegradation of autotoxicity allelochemicals and xenobiotics as it is the first to describe a degrading bacterium of 11 types of allelochemicals and xenobiotics and their great potential in improving tobacco continuous obstacles.

Crop diversification promotes soil aggregation and carbon accumulation in global agroecosystems: A meta-analysis

Soil aggregation contributes to the stability of soil structure and the sequestration of soil organic carbon (SOC), making it an important indicator of soil health in agroecosystems. Crop diversification is considered a rational management practice for promoting sustainable agriculture. However, the complexity of cropping systems and crop species across different regions limits our comprehensive understanding of soil aggregation and associated carbon (C) content under crop diversification. Therefore, we conducted a meta-analysis by integrating 1924 observations from three diversification strategies (cover crops, crop rotation, and intercropping) in global agroecosystems to explore the effects of crop diversification on soil aggregates and associated C content. The results showed that compared to monoculture, crop diversification significantly increased the mean weight diameter and bulk soil C by 7.5% and 3.3%, respectively. Furthermore, there was a significant increase in the proportion of macroaggregates and their associated C content by 5.0% and 12.5%, while there was a significant decrease in the proportion of microaggregates as well as silt-clay fractions along with their associated C under crop diversification. Through further analysis, we identified several important factors that influence changes in soil aggregation and C content induced by crop diversification including climatic conditions, soil properties, crop species, and agronomic practices at the experimental sites. Interestingly, no significant differences were found among the three cropping systems (cover crops, crop rotation, and intercropping), while the effects induced by crop diversifications showed relatively consistent results for monoculture crops as well as additive crops and crop diversity. Moreover, the impact of crop diversification on soil aggregates and associated C content is influenced by soil properties such as pH and SOC. In general, our findings demonstrate that crop diversification promotes soil aggregation and enhances SOC levels in agroecosystems worldwide.

Microbial degradation of plant toxins

Plants produce a variety of secondary metabolites in response to biotic and abiotic stresses. Although they have many functions, a subclass of toxic secondary metabolites mainly serve plants as deterring agents against herbivores, insects, or pathogens. Microorganisms present in divergent ecological niches, such as soil, water, or insect and rumen gut systems have been found capable of detoxifying these metabolites. As a result of detoxification, microbes gain growth nutrients and benefit their herbivory host via detoxifying symbiosis. Here, we review current knowledge on microbial degradation of toxic alkaloids, glucosinolates, terpenes, and polyphenols with an emphasis on the genes and enzymes involved in breakdown pathways. We highlight that the insect-associated microbes might find application in biotechnology and become targets for an alternative microbial pest control strategy.

Plant and soil-associated microbiome dynamics determine the fate of bacterial wilt pathogen Ralstonia solanacearum

MAIN CONCLUSION

Plant and the soil-associated microbiome is important for imparting bacterial wilt disease tolerance in plants. Plants are versatile organisms that are endowed with the capacity to withstand various biotic and abiotic stresses despite having no locomotory abilities. Being the agent for bacterial wilt (BW) disease, Ralstonia solanacearum (RS) colonizes the xylem vessels and limits the water supply to various plant parts, thereby causing wilting. The havoc caused by RS leads to heavy losses in crop productivity around the world, for which a sustainable mitigation strategy is urgently needed. As several factors can influence plant-microbe interactions, comprehensive understanding of plant and soil-associated microbiome under the influence of RS and various environmental/edaphic conditions is important to control this pathogen. This review mainly focuses on microbiome dynamics associated with BW disease and also provide update on microbial/non-microbial approaches employed to control BW disease in crop plants.