A new broad-spectrum powdery mildew resistance allele Pm2c was identified and mapped in Chinese wheat landrace Niaomai. Chinese wheat landrace Niaomai showed resistance to 27 of 28 Chinese Blumeria graminis f. sp tritici (Bgt) races. Genetic analysis of an F2 population and its derived F2:3 families from the cross Niaomai × Mingxian 169 and backcross population, Niaomai/2*Mingxian 169, indicated that the resistance of Niaomai to Bgt races was conferred by a single dominant resistance gene, temporarily designated PmNM. Molecular tagging showed that PmNM was located on chromosome 5DS and flanked by SSR markers Xcfd81 and Xcfd78 with the genetic distances of 0.1/0.4 cM and 4.9/7.5 cM, respectively. Niaomai showed a different array of responses compared to lines with Pm2a, Pm2b, PmD57-5D, PmLX66, PmX3986-2 and Pm48 genes, sharing the same Xcfd81 allele but differing from Xcfd78 allele for Pm2a and Pm2b lines. Allelism tests based on crosses of Niaomai with Ulka/8*Cc and KM2939 showed that PmNM is allelic to Pm2a and Pm2b. We concluded that PmNM is a new allele of Pm2, re-designated Pm2c. Pm2c could be transferred into wheat cultivars by marker-assisted selection to improve the powdery mildew resistance of breeding cultivars/lines.
Common root rot, caused by Bipolaris sorokiniana, is one of the most prevalent diseases of wheat and has led to major declines in wheat yield and quality worldwide. Here, strain XZ34-1 was isolated from soil and identified as Bacillus amyloliquefaciens based on the morphological, physiological, biochemical characteristics and 16S rDNA sequence. Culture filtrate (CF) of strain XZ34-1 showed a high inhibition rate against B.sorokiniana and had a broad antifungal spectrum. It also remarkably inhibited the mycelial growth and spore germination of B. sorokiniana. In pot control experiments, the incidence and disease index of common root rot in wheat seedlings were decreased after treatment with CF, and the biological control efficacy was significant, up to 78.24%. Further studies showed XZ34-1 could produce antifungal bioactive substances and had the potential of promoting plant growth. Lipopeptide genes detection with PCR indicated that strain XZ34-1 may produce lipopeptides. Furthermore, activities of defense-related enzymes were enhanced in wheat seedlings after inoculation with B.sorokiniana and treatment with CF, which showed induced resistance could be produced in wheat to resist pathogens. These results reveal that strain XZ34-1 is a promising candidate for application as a biological control agent against B.sorokiniana.
CGA-N12 (the amino acid sequence from the 65th to the 76th residue of the N-terminus of chromagranin A) is an antifungal peptide derived from human chromogranin A (CGA). In our previous investigation, CGA-N12 was found to have specific anti-candidal activity, though the mechanism of action remained unclear. Here, we investigated the effects of CGA-N12 on mitochondria. We found that CGA-N12 induced an over-generation of intracellular reactive oxygen species and dissipation in mitochondrial membrane potential, in which the former plays key roles in the initiation of apoptosis and the latter is a sign of the cell apoptosis. Accordingly, we assessed the apoptosis features of Candida tropicalis cells after treatment with CGA-N12 and found the following: leakage of cytochrome c and uptake of calcium ions into mitochondria and the cytosol; metacaspase activation; and apoptotic phenotypes, such as chromatin condensation and DNA degradation. In conclusion, CGA-N12 is capable of inducing apoptosis in C. tropicalis cells through mitochondrial dysfunction and metacaspase activation. Antifungal peptide CGA-N12 from human CGA exhibits a novel apoptotic mechanism as an antifungal agent.
Rhizoctonia cerealis is a major fungal pathogen of wheat that causes great yield losses in all wheat-growing regions of the world. The biocontrol agent Bacillus subtilis XZ18-3 was investigated for inhibiting R. cerealis growth in wheat. The results of the mycelial growth test showed that the sterile filtrate of B. subtilis XZ18-3 could significantly inhibit the mycelial growth of R. cerealis and cause swelling and rupture of the mycelium. Observation by transmission electron microscopy indicated that the sterile filtrate could penetrate the cellular membrane of Rhizoctoniacerealis, resulting in organelle destruction. The effect of the sterile filtrates on the pathogen cells, shown through fluorescent microscopy using different stains, revealed the mechanism by which the sterile filtrate caused DNA fragmentation, accumulation of ROS and changes in cell membrane permeability. To reach a better treatment of the soil-borne fungi, the components of a wettable powder were screened and an optimised formula determined (30.0% kaolin, 4.0% polyvinyl alcohol, 8.0% Tween-80, 2.0% polyethylene glycol and 100% fermentation broth). A quality index analysis revealed that the wetting powder reached acceptable biological pesticide standards. Pot control experiments showed that the wettable powder of B. subtilis XZ18-3 effectively controlled the pathogens with an efficacy of 88.28%. This study has provided the potential biocontrol agents (BCAs) for wheat sharp eyespot disease.
Rehmannia glutinosa production is affected by replanting disease, in which autotoxic harm to plants is mediated by endogenous phenolic acids as allelopathic compounds found in root exudates. These phenolic acids are mostly phenylpropanoid products of plants’ secondary metabolisms. The molecular mechanism of their biosynthesis and release has not been explored in R. glutinosa. P-coumarate-3-hydroxylase (C3H) is the second hydroxylase gene involved in the phenolic acid/phenylpropanoid biosynthesis pathways. C3Hs have been functionally characterized in several plants. However, limited information is available on the C3H gene in R. glutinosa. Here, we identified a putative RgC3H gene and predicted its potential function by in silico analysis and subcellular localization. Overexpression or repression of RgC3H in the transgenic R. glutinosa roots indicated that the gene was involved in allelopathic phenolic biosynthesis. Moreover, we found that these phenolic acid release amount of the transgenic R. glutinosa roots were altered, implying that RgC3H positively promotes their release via the molecular networks of the activated phenolic acid/phenylpropanoid pathways. This study revealed that RgC3H plays roles in the biosynthesis and release of allelopathic phenolic acids in R. glutinosa roots, laying a basis for further clarifying the molecular mechanism of the replanting disease development.
Infections with multidrug‐resistant (MDR) pathogens are increasingly concerning for public health. Synthesized antimicrobial peptide A4 (SAMP‐A4), a peptide computationally designed by our research team, is a potential drug candidate. However, the antimicrobial peptide SAMP‐A4 is easily degraded in serum. To obtain SAMP‐A4 analogues with high biostability, chemical modifications at its N‐terminus, including fatty acid conjugation, glycosylation and PEGylation, were carried out. The results showed that the introduction of hydrophobic fatty acids at the N‐terminus of SAMP‐A4 is better than hydrophilic glycosylation and PEGylation. With increasing fatty acid chain length, the stability of SAMP‐A4 analogues in serum and trypsin solutions is significantly improved, and the activities against MDR bacteria and Candida are significantly enhanced. There is no obvious change in haemolysis even when hexanoic acid is coupled with SAMP‐A4, so the resulting analogue SAMP‐A4‐C6, SAMP‐A4 conjugated with hexanoic acid, is the most likely of the analogues to become a drug.
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