Advances of miRNA-mediated regulatory roles in plant-microbe interaction / 生物工程学报

There are many bidirectional communication and crosstalk between microbes and host plants. The plant-pathogen interaction directly affects the survival of host plants, while the interaction between plants and their probiotics benefits both. Plant miRNA responds quickly to pathogenic or beneficial microbes when they enter the plant tissues, while microbes also produce miRNA-like RNA (milRNA) to affect plant health. These means miRNA or milRNA is an important fast-responding molecular mediator in plant-microbe interactions, and these internal mechanisms have been better understood in recent years. This review summarized the regulatory roles of miRNA in plant-pathogens and plant-probiotics interaction. The regulatory role of miRNA in disease resistance of host plants during plant-pathogens interaction, and the regulatory role of miRNA in promoting host growth and development during plant-probiotics interaction, as well as the cross-kingdom regulatory role of milRNA in host plants, were discussed in-depth.

Population Dynamics and Diversity of Endophytic Bacteria Associated with Soybean (Glycine max (L) Merril).

Aim: Endophytic bacterial population and their diversity in soybean were investigated. Study Design: Endophytic population was assessed during different growth stages of soybean (CV JS 335) viz., vegetative and reproductive stages. Place and Duration of Study: Microbiology Research Laboratory, Department of Microbiology, R. A. Mahavidyalaya, Washim (MS), India, during the cultivation period of June-December 2010. Methodology: Healthy plants of soybean were screened from the different locations of Washim district (M. S., India). Samples represent each growth stage viz., vegetative (V1- V5) and reproductive (R1-R8) were collected. Population densities were expressed as log10 colony forming units (CFU) g-1 fresh weight. The isolates were identified to genus level according to Bergey’s Manual of Determinative Bacteriology on the basis morphological, cultural and biochemical characteristics. Results: The maximum endophytic population was recorded for vegetative stage at V5 and V4 (5.74 and 5.01 log10 CFU g-1 fresh weight) and for reproductive stage at R2, R1 and R3 (5.84, 5.80 and 5.74 log10 CFU g-1 fresh weight). A total of 572 (35.50 %) from vegetative growth stages and 1039 (64.50 %) from reproductive growth stages bacterial isolates were obtained. The endophytic isolates were identified as members belonging to the genera Pseudomonas, Bacillus, Enterobacter, Klebsiella, Acetobacter Burkholderia, Rhizobium and Xanthomonas. Conclusion: As soybean development progresses endophytic population increased. At maturity, the high population density was observed and thereafter the population declined.

Growth responses of in vitro Fusarium oxysporum f. sp. niveum to external supply of tannic acid.

Allelochemicals released from root exudates or decaying residues of plants play diversified roles in ecological interactions of plant-pathogen. The objective of this work was to evaluate the allelopathic effect of an externally supplied tannic acid on soil-borne in vitro Fusarium oxysporum f.sp.niveum. Results showed that the tannic acid decreased the growth of the fungus up to 9.5% at 800 mg l-1. Conidial germination was reduced by 52.3% in comparison with the control. However, sporulation and mycotoxin production by the fungus were stimulated. The activity of pectinase and proteinase were initially increased and finally decreased with increase in concentrations of tannic acid. Tannic acid served as an ecological allelochemical, repressing the growth of the pathogen.

Plant-enhanced phenanthrene and pyrene biodegradation in acidic soil.

A study was undertaken to assess if corn plant (Zea may L.) may be able to enhance the degradation of phenanthrene and pyrene in acidic soil inoculated with a bacterial strain (Pseudomonas putida MUB1) capable of degrading polycyclic aromatic hydrocarbons (PAHs). Planting with corn, inoculating with MUB1, or a combination of the two were found to promote the degradation of phenanthrene and pyrene in acidic soil at different rates. In the presence of corn plants, the rates of phenanthrene and pyrene removal were 41.7 and 38.8% in the first 10 days, while the rates were 58.8 and 53.6%, respectively, in the treatment which received MUB1 only. After 60 days, the corn + MUB1 treatment led to the greatest reduction in both phenanthrene and pyrene biodegradation (89 and 88.2%, respectively). In control autoclaved soil, the rates of phenanthrene and pyrene removal were 14.2 and 28.7%, respectively, while in non-autoclaved soil, the rates were 68.7 and 53.2%, respectively. These results show that corn, which was previously shown to grow well in PAH-contaminated acidic soil, also can enhance PAH degradation in such soil. Inoculation with a known PAH degrader further enhanced PAH degradation in the presence of corn.

Growth of in vitro Fusarium oxysporum f. sp. niveum in chemically defined media amended with gallic acid

Gallic acid was artificially added to the media to grow Fusarium oxysporum f.sp.niveum to investigate its effect on the pathogenic fungus. Results indicate that gallic acid inhibited the growth of F. oxysporum f.sp.niveum. The colony diameter, the conidia germinating rate and the conidia yield were reduced by 5.7-22.9 percent percent, 35.8-55.6 percent and 38.9-62.2 percent respectively. However, the virulence factors by the fungus were stimulated. The activity of pectinase, proteinase and cellulase increased by 12.3-627.8 percent, 11.8-41.2 percent and 0.5-325.0 percent respectively, while the activity of amylase increased slightly. The results suggest that gallic acid repressed growth but facilitated the relative pathogenicity of invading pathogens.