Abstract
BackgroundPseudostellaria heterophylla (P. heterophylla), a herbaceous perennial, belongs to Caryophyllaceae family and is one of the Chinese herbal medicine with high pharmacodynamic value. It can be used to treat the spleen deficiency, anorexia, weakness after illness and spontaneous perspiration symptoms. Our previous study found that consecutive monoculture of Pseudostellaria heterophylla could lead to the deterioration of the rhizosphere microenvironment. The specialized forms of pathogenic fungus Fusarium oxysporum f.Sp. heterophylla (F. oxysporum) in rhizosphere soils of P. heterophylla plays an important role in the consecutive monoculture of P. heterophylla.ResultsIn this study, F. oxysporum was used to infect the tissue culture plantlets of P. heterophylla to study the responding process at three different infection stages by using RNA-sequencing. We obtained 127,725 transcripts and 47,655 distinct unigenes by de novo assembly and obtained annotated information in details for 25,882 unigenes. The Kyoto Encyclopedia of Genes and Genomes pathway analysis and the real-time quantitative PCR results suggest that the calcium signal system and WRKY transcription factor in the plant-pathogen interaction pathway may play an important role in the response process, and all of the WRKY transcription factor genes were divided into three different types. Moreover, we also found that the stimulation of F. oxysporum may result in the accumulation of some phenolics in the plantlets and the programmed cell death of the plantlets.ConclusionsThis study has partly revealed the possible molecular mechanism of the population explosion of F. oxysporum in rhizosphere soils and signal response process, which can be helpful in unraveling the role of F. oxysporum in consecutive monoculture problems of P. heterophylla.
Highlights
Pseudostellaria heterophylla (P. heterophylla), a herbaceous perennial, belongs to Caryophyllaceae family and is one of the Chinese herbal medicine with high pharmacodynamic value
Abundance of F. oxysporum in different rhizosphere soil and its infection to the plants We used the quantitative real time PCR in the analysis of the abundance of F. oxysporum in different rhizosphere soil, the results indicated that the abundance of F. oxysporum in two-year monoculture soil (SM) was much higher than the newly planted soil (NP) and control soil (CK), the amount of F. oxysporum in twoyear monoculture soil (SM) was 2.3 times higher than that in newly planted soil (NP), and all of the differences reached an extremely significant level (P ≤ 0.01) (Fig. 1)
Since we inoculated the pathogen on the medium about 2–3 cm away from the roots of plants, the pathogenic fungi F. oxysporum initiated to contact with roots about three days later, the leaves start to turn yellow about one week later and the basal part of the stem was covered with F. oxysporum and the plants died two weeks later (Fig. 2a)
Summary
Pseudostellaria heterophylla (P. heterophylla), a herbaceous perennial, belongs to Caryophyllaceae family and is one of the Chinese herbal medicine with high pharmacodynamic value. It has been reported that a wide variety of compounds exudated from the roots of the monocultured plants, could be degraded or transformed to other allelochemicals, thereby orchestrate the soil microbial community in their immediate vicinity Due to this reason, chemical and physical properties of the soil alters, retard the growth and development, which leads to the yield and quality decline of the medicinal plants [6, 9,10,11,12,13]. Wu et al [13] discovered that mixed phenolic acid could promote mycelial growth, sporulation and toxin production of pathogenic F. oxysporum, implying that the allelochemicals including phenolic acids, organic acids, etc., released in the root exudates by the monocultured plants might mediate the differential changes of microbial flora in rhizosphere soil under monoculture cropping system
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