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Wheat powdery mildew caused by Blumeria graminis f. sp. tritici ( Bgt) is one of the most serious wheat diseases in the world. Biological control is considered an environmentally safe approach to control plant diseases. Here, to develop effective biocontrol agents for controlling wheat powdery mildew, antagonistic strain XZ16-1 was isolated and identified as Bacillus subtilis based on the morphological, biochemical, and physiological characteristics and 16S rDNA sequence. The culture filtrate of B. subtilis XZ16-1 and its extracts had a significant inhibitory effect on the spore germination of Bgt. Moreover, the therapeutic and prevention efficacy of the 100% culture filtrate on wheat powdery mildew reached 81.18 and 83.72%, respectively, which was better than that of chemical fungicide triadimefon. Further antimicrobial mechanism analysis showed that the XZ16-1 culture filtrate could inhibit the development of powdery mildew spores by disrupting the cell membrane integrity, causing reductions in the mitochondrial membrane potential, and inducing the accumulation of reactive oxygen species in the spores. Biochemical detection indicated that XZ16-1 could solubilize phosphate, fix nitrogen, and produce hydrolases, lipopeptides, siderophores, and indole-3-acetic acid. Defense-related enzymes activated in wheat seedlings treated with the culture filtrate indicated that disease resistance was induced in wheat to resist pathogens. Furthermore, a 106 CFU/ml suspension of XZ16-1 increased the height, root length, fresh weight, and dry weight of wheat seedlings by 77.13, 63.46, 76.73, and 19.16%, respectively, and showed good growth-promotion properties. This study investigates the antagonistic activity and reveals the action mechanism of XZ16-1, which can provide an effective microbial agent for controlling wheat powdery mildew.

The yield and quality of the medicinal plant Achyranthes bidentata can be increased when it is replanted into a field cultivated previously with the same crop, however, fundamental aspects of its biology (so-called “replanting benefit”) still remain to be elucidated. miRNAs are sRNA molecules involved in the post-transcriptional regulation of gene expression in plant biological processes. Here, 267 conserved and 36 novel miRNAs were identified in A. bidentata roots. We compared the miRNA content of the roots (R1) from first-year planting with that of the roots (R2) of second-year replanting, and screened 21 differentially expressed (DE) miRNAs. Based on in silico functional analysis, integrated miRNA-mRNA datasets allowed the identification of 10 miRNA-target family modules, which might participate in the benefit. The expression profiles of the miRNA-target modules were potentially correlated with the presence of the replanting benefit. The indication was that the miRNA-responsive continuous monoculture could reprogram miRNA-mRNA expression patterns, which possibly promote the root growth and development, enhance its transport activity and strengthen its tolerance to various stresses, thereby improving A. bidentata productivity as observed in the replanting benefit. Our study provides basic data for further research on the molecular mechanisms of the benefit in A. bidentata.

Chromogranin A (CGA)-N46, a derived peptide of human chromogranin A, has antifungal activity. To further research the active domain of CGA-N46, a series of derivatives were designed by successively deleting amino acid from both terminus of CGA-N46, and the amino acid sequence of each derivative was analyzed by bioinformatic software. Based on the predicted physicochemical properties of the peptides, including half-life time in mammalian reticulocytes (in vitro), yeast (in vivo) and E. coli (in vivo), instability index, aliphatic index and grand average of hydropathicity (GRAVY), the secondary structure, net charge, the distribution of hydrophobic residues and hydrophilic residues, the final derivatives CGA-N15, CGA-N16, CGA-N12 and CGA-N8 were synthesized by solid-phase peptide synthesis. The results of bioinformatic analysis showed that CGA-N46 and its derivatives were α-helix, neutral or weak positive charge, hydrophilic, and CGA-N12 and CGA-N8 were more stable than the other derivatives. The results of circular dichroism confirmed that CGA-N46 and its derived peptides displayed α-helical structure in an aqueous solution and 30 mM sodium dodecylsulfate, but α-helical contents decreased in hydrophobic lipid vesicles. CGA-N15, CGA-N16, CGA-N12 and CGA-N8 had higher antifungal activities than their mother peptide CGA-N46. Among of the derived peptides, CGA-N12 showed the least hemolytic activity. In conclusion, we have successfully identified the active domain of CGA-N46 with strong antifungal activity and weak hemolytic activity, which provides the possibility to develop a new class of antibiotics.

The transcriptome profiling in replanting roots revealed that expression pattern changes of key genes promoted important metabolism pathways, antioxidant and pathogen defense systems, adjusted phytohormone signaling and inhibited lignin biosynthesis. The yield of the medicinal plant Achyranthes bidentata could be significantly increased when replanted into a field cultivated previously for the same crop, but the biological basis of this so-called “replanting benefit” is unknown. Here, the RNA-seq technique was used to identify candidate genes responsible for the benefit. The analysis of RNA-seq libraries prepared from mRNA extracted from the roots of first year planting (normal growth, NG) and second year replanting (consecutive monoculture, CM) yielded about 40.22 GB sequencing data. After de novo assembly, 87,256 unigenes were generated with an average length of 1060 bp. Among these unigenes, 55,604 were annotated with public databases, and 52,346 encoding sequences and 2881 transcription factors were identified. A contrast between the NG and CM libraries resulted in a set of 3899 differentially transcribed genes (DTGs). The DTGs related to the replanting benefit and their expression profiles were further analyzed by bioinformatics and qRT-PCR approaches. The major differences between the NG and CM transcriptomes included genes encoding products involved in glycolysis/gluconeogenesis, glutathione metabolism and antioxidant defense, in aspects of the plant/pathogen interaction, phytohormone signaling and phenylpropanoid biosynthesis. The indication was that replanting material enjoyed a stronger level of defense systems, a balance regulation of hormone signals and a suppression of lignin formation, thereby promoting root growth and development. The study provides considerable significant insights for a better understanding of the molecular mechanism of the replanting benefit and suggests their possible application in developing methods to reinforce the effects in medicinal plants.

The perennial herbaceous plant, Rehmannia glutinosa Libosch, is a traditional Chinese medicine because of the active extracts from its dried tuberous roots. However, R. glutinosa productivity and quality has been seriously affected by replanting (continuous monoculture) disease, which cannot at present be effectively prevented or controlled. Since very little is known about the molecular mechanism of replanting disease, we aimed to investigate transcriptional changes in replanted R. glutinosa leaves and identify genes responding to the disease. Here, we constructed a cDNA library from total RNA isolated from the mixture of leaves of the first year planted (L1) and the second year replanted R. glutinosa (L2) at the tuberous root expansion stage. We generated about 37 million high-quality reads from the cDNA library using deep sequencing and obtained 94,544 distinct sequences by de novo assembly and gap-filling. From this set, a total of 54,490 transcripts containing a complete or partial encoding region was annotated in public protein databases. Based on this resource, we screened differentially expressed genes in the L1 and L2 libraries by the digital gene expression (DGE) technique. Finally, a set of 1,954 genes was found to be differentially expressed in L2. Using bioinformatics and qRT-PCR, the 117 most strongly differentially expressed genes were considered to be prime candidates responsible for replanting disease. Functional analysis of the candidates showed that ethylene signaling was exaggerated and the genes in key metabolism pathways were abnormally expressed in L2. The study provides an important resource for further investigating the cause of replanting disease and developing methods to control or reduce its harmful effects.