Genome-Wide Identification and Characterization of Calcium Metabolism Related Gene Families in Arabidopsis thaliana and Their Regulation by Bacillus amyloliquefaciens Under High Calcium Stress.

Several gene families involved in calcium signaling have been detected in plants, including calmodulin (CaM), calcium dependent protein kinases (CDPK), calcineurin B-like (CBL) and cyclic nucleotide-gated channels (CNGCs). In our previous study, we demonstrated that Bacillus amyloliquefaciens LZ04 (B. amyloliquefaciens LZ04) regulate genes involved in calcium stress in Arabidopsis thaliana (A. thaliana). Here, we aimed to explore the potential involvement of calcium-related gene families in the response of A. thaliana to calcium stress and the potential regulatory effects of B. amyloliquefaciens LZ04 on these genes. The structure, duplication, synteny, and expression profiles of 102 genes in calcium-related gene families in A. thaliana were investigated. Hidden Markov Models (HMMs) and BLASTP were used to predict candidate genes and conserved domains of the candidate genes were confirmed in SMART and NCBI CDD databases. Gene duplications and synteny were uncovered by BLASTP and phylogenetic analysis. The transcriptome expression profiles of candidate genes were investigated by strand-specific sequencing. Cluster analysis was used to find the expression profiles of calcium-related genes families under different treatment conditions. A total of 102 genes in calcium-related gene families were detected in A. thaliana genome, including 34 CDPK genes, 20 CNGC genes, 18 CIPK genes, 22 IQD genes, and 10 CBP genes. Additionally, of the 102 genes, 33 duplications (32.35%) and 26 gene pairs including 48 genes (47.06%) were detected. Treatment with B. amyloliquefaciens LZ04 enhanced the resistance of A. thaliana under high calcium stress by regulating some of the genes in the calcium-related gene families. Functional enrichment analysis revealed that the genes clustered in the 42nd expression profile which may be B. amyloliquefaciens-responsive genes under calcium stress were enriched in protein phosphorylation and protein modification process. Transcriptome data was validated by RT-PCR and the results generally corroborated the transcriptome sequencing results. These results may be useful for agricultural improvement in high calcium stress regions.

Bacillus amyloliquefaciens PDR1 from root of karst adaptive plant enhances Arabidopsis thaliana resistance to alkaline stress through modulation of plasma membrane H+-ATPase activity.

Exploration of native microbes is a feasible way to develop microbial agents for ecological restoration. This study was aimed to explore the impact of Bacillus amyloliquefaciens PDR1 from karst adaptive plant on the activity of root plasma membrane H+-ATPase in Arabidopsis thaliana. A. thaliana was cultured in presence or absence of B. amyloliquefaciens PDR1 and its effects on the growth were evaluated by measuring the taproot length and dry weight. The rhizosphere acidification capacity was detected by a pH indicator, a pH meter and non-invasive micro-test techniques (NMT). The nutrient uptake was performed using appropriate methods. A combination of transcriptome sequencing and real-time quantitative polymerase chain reaction (qRT-PCR) was used to measure the expression of functional genes that regulate the plasma membrane H+-ATPase activity in A. thaliana roots. Functional analysis was performed to understand how B. amyloliquefaciens regulates biological processes and metabolic pathways to strengthen A. thaliana resistance to alkaline stress. Here, we show that volatile organic compounds (VOCs) from B. amyloliquefaciens PDR1 promoted the growth and development of A. thaliana, enhanced the plasma membrane H+-ATPase activity, and affected ion absorption in Arabidopsis roots. Moreover, B. amyloliquefaciens PDR1 VOCs did not affect the expression of the gene coding for plasma membrane H+-ATPase, but affected the expression of genes regulating the activity of plasma membrane H+-ATPase. Our findings illuminate the mechanism by which B. amyloliquefaciens regulates the growth and alkaline stress resistance of A. thaliana, and lay a foundation for wide and efficient application for agricultural production and ecological protection.

Bacillus amyloliquefaciens LZ04 improves the resistance of Arabidopsis thaliana to high calcium stress and the potential role of lncRNA-miRNA-mRNA regulatory network in the resistance.

Bacillus amyloliquefaciens is a non-pathogenic and plant growth-promoting rhizobacterium that enhances plant resistance to drought and diseases. Arabidopsis thaliana is a multipurpose model plant for exploring microorganism-plant interactions and a crucial vegetal tool for molecular research. Non-coding RNAs are RNA molecules involved in the regulation of various biological functions and constitute a research hotspot in the field of plant biology. In this study, the effect of B. amyloliquefaciens treatment on the resistance of A. thaliana to high calcium stress was analyzed. The transcriptome sequencing of A. thaliana roots under four treatment conditions was performed to screen differentially expressed lncRNAs, mRNAs and miRNAs. Functional analysis was also performed to understand the potential mechanism by which B. amyloliquefaciens-regulated lncRNAs, miRNAs and mRNAs affect the resistance of A. thaliana to high calcium stress. The results indicated that B. amyloliquefaciens treatment increased the resistance of A. thaliana to high calcium stress. A set of differentially expressed lncRNAs, mRNAs and miRNAs were screened between the high calcium and control group on one hand, and high calcium and high calcium + B. amyloliquefaciens groups on the other hand. Functional analysis indicated that the differentially expressed mRNAs and miRNA were involved in various biological functions and that transcriptional dysregulation caused by high calcium stress involves metabolic processes rather than defense responses. Conclusively, B. amyloliquefaciens may improve the resistance of A. thaliana to high calcium stress via a lncRNA-miRNA-mRNA regulatory network. These findings will contribute to the development of agriculture in karst regions with high calcium content.