In recent years, the optimum development of land resources has become an important task for ensuring the security of food production in China. Soil microorganisms have been considered to play an important role in conferring soil fertility and productivity. In order to obtain the plant-growth-promoting bacteria in newly reclaimed land, a total of 988 bacterial strains were isolated from nine soil samples collected from different sites in wastelands in Hangzhou (Zhejiang Province, China), a rural mountainous area. Among them, five strains exhibited substantial potential of phosphate solubilization, nitrogen fixation, siderophore production and indole acetic acid production at both pH 5.0 and pH 7.0, and also promoted eggplant growth in immature soil from newly reclaimed land. Furthermore, bacterial strains ZJ62 and ZJ3-12 were identified as Pantoeadispersa and Pantoea ananatis, respectively, while strains ZJ5, ZJ9 and ZJ174 were identified as Burkholderiaarboris, Burkholderia pyrrocinia and Burkholderia pyrrocinia, respectively, based on colony morphology observation and phylogenetic analysis of 16S rDNA and the housekeeping genes sequences. Overall, the result of this study showed that the 5 obtained bacterial strains have a great potential in promoting plant growth in immature soil from newly reclaimed land.
IntroductionPakchoi is an important leafy vegetable in China. Due to industrialization and urbanization, pakchoi has been cultivated in newly reclaimed mountainous lands in Zhejiang Province, China in recent years. However, immature soil is not suitable for plant growth and needs to be modified by the application of different organic fertilizer or microbial fertilizer based plant-growth-promoting microbe. In 2021, a high efficient plant-growth-promoting fungi (PGPF; Aspergillus brunneoviolaceus HZ23) was obtained from newly reclaimed land of Zhejiang Province, China. In order to valuate microbial fertilizer based A. brunneoviolaceus HZ23 (MF-HZ23) on pakchoi growth in immature soil, we investigated the effect of MF-HZ23 on soil properties, rhizosphere bacterial community structure, and metabolites of pakchoi rhizosphere soil samples.MethodsThe field experiment (four treatments, MF-HZ23, MF-ZH23 + CCF, CCF and the control) was completely randomly designed and carried out on newly reclaimed land in Yangqingmiao Village of Fuyang district, Hangzhou City, Zhejiang Province, China. In order to evaluate the influence of microbial fertilizer based A. brunneoviolaceus HZ23 on pakchoi in the newly reclaimed land, the number of pakchoi leaves, total fresh and dry weight of the seedlings was counted. In addition, the soil properties, including the pH, OMC, total N, AHN, available P, the genome sequencing, and metabolomics assay were also detected.ResultsThe results revealed a significant difference between MF-HZ23 and the control in soil properties, bacterial community structure, and metabolites. Indeed, compared with the control, MF-HZ23 caused 30.66, 71.43, 47.31, 135.84, and 2099.90% increase in the soil pH, organic matter contents (OMC), total nitrogen (N), alkaline hydrolysis nitrogen (AHN), and available phosphorus (P), respectively. Meanwhile, MF-HZ23 caused 50.78, 317.47, and 34.40% increase in the relative abundance of Proteobacteria, Bacteroidota, and Verrucomicrobiota and 75.55, 23.27, 69.25, 45.88, 53.42, and 72.44% reduction in the relative abundance of Acidobacteriota, Actinobacteriota, Chloroflexi, Planctomycetota, Patescibacteria, and WPS-2, respectively, compared with the control based on 16S amplicon sequencing of soil bacteria. Furthermore, redundancy discriminant analysis (RDA) of bacterial communities and soil properties indicated that the main variables of bacterial communities included available P, AHN, pH, OMC, and total N. In addition, non-targeted metabolomics techniques (UHPLC–MS analysis) revealed that MF-HZ23 resulted in a great change in the kinds of metabolites in the rhizosphere soil. Indeed, in MF-HZ23 and the control group, there were six differentially expressed metabolites (DEMs) belong to organoheterocyclic compounds, organic acids and derivatives, organic nitrogen compounds, and these six DEMs were significantly positively correlated with 23 genus of bacteria, which showed complicated interactions between bacteria and DEMs in pakchoi rhizosphere soil.ConclutionsOverall, the results of this study revealed significant modification in physical, chemical, and biological properties of pakchoi soil. Microbial fertilizer based PGPF A. brunneoviolaceus HZ23 (MF-HZ23) can be used as a good amendment for newly reclaimed land.
SaNramp6 in Sedum alfredii encodes a membrane-localized metal transporter. We isolated the SaNramp6h allele from the hyperaccumulating ecotype (HE) of S. alfredii. When this allele was expressed in transgenic yeast and Arabidopsis thaliana, it enhanced their cadmium (Cd) sensitivity by increased Cd transport and accumulation. We isolated another allele, SaNramp6n, from a nonhyperaccumulating ecotype (NHE) of S. alfredii. Amino acid sequence comparisons revealed three amino acid differences between SaNramp6h and SaNramp6n. We investigated the Cd transport activity of the Nramp6 allele, and determined which residues are essential for the transport activity. We conducted structure-function analyses of SaNramp6 based on site-directed mutagenesis and functional assays of the mutants in yeast and Arabidopsis. The three residues that differed between SaNramp6h and SaNramp6n were mutated. Only the L157P mutation of SaNramp6h impaired Cd transport. The other mutations, S218N and T504A, did not affect the transport activity of SaNramp6h, indicating that these residues are not essential for metal selectivity. Transgenic plants overexpressing SaNramp6hL157P showed altered metal accumulation in shoots and roots. Our results suggest that the conserved site L157 is essential for the high metal transport activity of SaNramp6h. This information may be useful for limiting or increasing Cd transport by other plant natural resistance associated macrophage protein (NRAMP) proteins.
Targeted genome editing technologies are becoming the most important and widely used genetic tools in studies of phytopathology. The “clustered regularly interspaced short palindromic repeats (CRISPR)” and its accompanying proteins (Cas) have been first identified as a natural system associated with the adaptive immunity of prokaryotes that have been successfully used in various genome-editing techniques because of its flexibility, simplicity, and high efficiency in recent years. In this review, we have provided a general idea about different CRISPR/Cas systems and their uses in phytopathology. This review focuses on the benefits of knock-down technologies for targeting important genes involved in the susceptibility and gaining resistance against viral, bacterial, and fungal pathogens by targeting the negative regulators of defense pathways of hosts in crop plants via different CRISPR/Cas systems. Moreover, the possible strategies to employ CRISPR/Cas system for improving pathogen resistance in plants and studying plant–pathogen interactions have been discussed.
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