Rhizosphere microbial diversity in rhizosphere of Pinellia ternata intercropped with maize

Structure and function of rhizosphere soil microbial communities associated with root rot of Knoxia roxburghii

The microbial communities in rhizosphere soil play important roles in plant health and crop productivity. However, the microbial community structure of rhizosphere soil still remains unclear. In this study, the composition, diversity and function of the microbial communities in the rhizosphere soil of healthy and diseased plants were compared using Illumina MiSeq high-throughput sequencing. The Sobs (richness) and Shannon (diversity) indices of the soil microbial communities were higher in the rhizospheres of 2- and 3-year-old susceptible plants than in those of the healthy plants. With the increase in planting time, the numbers of fungi tended to decrease, while those of the bacteria tended to increase. Fungal diversity could be used as a biological indicator to measure the health of Knoxia roxburghii. The microbial composition and differential analyses revealed that the rhizosphere soil infested with fungi had a higher relative abundance at the phylum level in Ascomycota and Basidiomycota, while the bacteria had a higher relative abundance of Chloroflexi and a lower relative abundance of Actinobacteriota. At the genus level, the rhizosphere soil infested with fungi had relatively more abundant unclassified_f__Didymellaceae and Solicoccozyma and relatively less abundant Saitozyma and Penicillium. The bacterial genus norank_f__Gemmatimonadaceae was the most abundant, while Arthrobacter was less abundant. In addition, the abundance of Fusarium in the fungal community varied (p = 0.001). It tended to increase in parallel with the planting years. Therefore, it was hypothesized that the change in the community composition of Fusarium may be the primary reason for the occurrence of root rot in K. roxburghii, and the change in the abundance of Fusarium OTU1450 may be an indication of the occurrence of root rot in this species. The community function and prediction analyses showed that the pathogenic fungi increased with the increase in planting years. In general, soil fungi can be roughly divided into three types, including pathotrophs, symbiotrophs, and saprotrophs. An analysis of the differences in the prediction of different rhizosphere functions showed that D and L were significantly different in the COG enrichment pathway of the K. roxburghii rhizosphere bacteria (p < 0.05). The soil physical and chemical properties, including the pH, AK, total potassium (TK), and catalase (S_CAT), had the most significant effect on the soil fungal community, and most of the soil physical and chemical properties significantly correlated with the bacterial community. This study demonstrated that the occurrence of root rot had an important effect on the diversity, structure and composition of microbial communities. In addition, the results will provide a theoretical basis to prevent and control root rot in K. roxburghii.

Assessing the biodiversity of rhizosphere and endophytic fungi in Knoxia valerianoides under continuous cropping conditions

BACKGROUND

Rhizosphere and endophytic fungi play important roles in plant health and crop productivity. However, their community dynamics during the continuous cropping of Knoxia valerianoides have rarely been reported. K. valerianoides is a perennial herb of the family Rubiaceae and has been used in herbal medicines for ages. Here, we used high-throughput sequencing technology Illumina MiSeq to study the structural and functional dynamics of the rhizosphere and endophytic fungi of K. valerianoides.

RESULTS

The findings indicate that continuous planting has led to an increase in the richness and diversity of rhizosphere fungi, while concomitantly resulting in a decrease in the richness and diversity of root fungi. The diversity of endophytic fungal communities in roots was lower than that of the rhizosphere fungi. Ascomycota and Basidiomycota were the dominant phyla detected during the continuous cropping of K. valerianoides. In addition, we found that root rot directly affected the structure and diversity of fungal communities in the rhizosphere and the roots of K. valerianoides. Consequently, both the rhizosphere and endophyte fungal communities of root rot-infected plants showed higher richness than the healthy plants. The relative abundance of Fusarium in two and three years old root rot-infected plants was significantly higher than the control, indicating that continuous planting negatively affected the health of K. valerianoides plants. Decision Curve Analysis showed that soil pH, organic matter (OM), available K, total K, soil sucrase (S_SC), soil catalase (S_CAT), and soil cellulase (S_CL) were significantly related (p < 0.05) to the fungal community dynamics.

CONCLUSIONS

The diversity of fungal species in the rhizosphere and root of K. valerianoides was reported for the first time. The fungal diversity of rhizosphere soil was higher than that of root endophytic fungi. The fungal diversity of root rot plants was higher than that of healthy plants. Soil pH, OM, available K, total K, S_CAT, S_SC, and S_CL were significantly related to the fungal diversity. The occurrence of root rot had an effect on the community structure and diversity of rhizosphere and root endophytic fungi.

Responses of soil nutrients and rhizosphere microbial communities of a medicinal plant Pinelliaternata to vermicompost

Vermicomposting is an important strategy for restoring soil function and fertility. However, information on the effects of vermicompost application in intensive Pinellia ternata planting systems has rarely been reported. Here, we focus on the effects of different vermicompost levels and chemical fertilizer (CF) strategies on soil chemical properties, soil enzymes, and soil rhizosphere microbial communities (bacteria and fungi) in a field experiment. Compared to no added fertilizers (CK), vermicompost was more effective than the CF treatment in increasing P. ternata yield. We found that the 5 t ha-1 vermicompost treatment (VC2) significantly increased the tuber yield by 44.43% and 6.55% compared to the CK and CF treatment, respectively, and water-soluble exudates by 6.56% and 9.63% (P < 0.05). The vermicompost and CF treatments significantly increased the total phosphorus (TP), urease (Ure), and soil catalase (Cat) contents (P < 0.05). Compared to the vermicompost and CK treatments, the CF treatment significantly decreased soil organic carbon (SOC), C/N ratio, and soil acid phosphatase (Pac) (P < 0.05). Redundancy analysis (RDA) showed that Ure and total potassium (TK) were the major drivers in the bacterial community, whereas TP, total nitrogen (TN), Pac, and TK were the major drivers in the fungal community. We also found a positive correlation between soil enzyme activities, including between Ure and bacterial genera (Clostridium, Pseudoclavibacter, Stella, Hyphomicrobium, Mesorhizobium, and Adlercreutzia). In summary, vermicompost application promotes P. ternata soil microecosystems and improves soil fertility, soil enzyme activities, and rhizosphere microbial structure and function. Vermicomposting is a novel and promising approach to sustainable ecological cultivation of Chinese herbs via the promotion of soil properties and beneficial organisms.

Biosynthetic pathways of triterpenoids and strategies to improve their Biosynthetic Efficiency

"Triterpenoids" can be considered natural products derived from the cyclization of squalene, yielding 3-deoxytriterpenes (hydrocarbons) or 3-hydroxytriterpenes. Triterpenoids are metabolites of these two classes of triterpenes, produced by the functionalization of their carbon skeleton. They can be categorized into different groups based on their structural formula/design. Triterpenoids are an important group of compounds that are widely used in the fields of pharmacology, food, and industrial biotechnology. However, inadequate synthetic methods and insufficient knowledge of the biosynthesis of triterpenoids, such as their structure, enzymatic activity, and the methods used to produce pure and active triterpenoids, are key problems that limit the production of these active metabolites. Here, we summarize the derivatives, pharmaceutical properties, and biosynthetic pathways of triterpenoids and review the enzymes involved in their biosynthetic pathway. Furthermore, we concluded the screening methods, identified the genes involved in the pathways, and highlighted the appropriate strategies used to enhance their biosynthetic production to facilitate the commercial process of triterpenoids through the synthetic biology method.