Xanthomonas oryzae pv. oryzae (Xoo) is an important pathogen in rice. C15surfactin A, produced by Bacillus velezensis HN-2, displayed antibacterial activity against Xoo and effectively inhibited its ...infection of rice. The median inhibitory concentration of C15surfactin A was 9.27 μg/mL. Scanning electron and transmission electron microscopy examination showed that C15surfactin A caused significant damage to the cell wall structure of Xoo cells. On the other hand, dramatic increases in the activity of phenylalanine ammonia-lyase (Pal) and H2O2 content were observed in rice leaves inoculated with Xoo from 0 h to 72 h. Quantitative PCR assays indicated that C15surfactin A exposure upregulated the expression of the genes Pr1a, CatA, and Pal. The results showed that C15surfactin A could inhibit the growth of Xoo and effectively induce rice resistance to Xoo by triggering a hypersensitive reaction (HR) via mediation of the activities of antioxidant-related enzymes. Taken together, C15surfactin A has strong antibiotic activity against Xoo and effectively induces rice resistance to Xoo. These results highlight the potential of C15surfactin A as a biocontrol agent against Xoo in rice.
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•C15surfactin A is major of secondary metabolites in Bacillus. It was isolated from Bacillus velezensis HN-2.•C15surfactin A has stronger antibacterial activity against Xanthomonas oryzae pv. oryzae.•C15surfactin A can effectively induce rice resistance to pathogen.•A series of biological methods to preliminary clarify the mechanism underlying C15surfactin A protective capability in rice
Main conclusion
A putative powdery mildew effector can elicit defense responses including reactive oxygen species and callose accumulations in model plants
Nicotiana benthamiana
and
Arabidopsis ...thaliana
and host plant
Hevea brasiliensis
.
Powdery mildew fungi cause severe diseases in many agricultural plants, such as the mildew fungus
Erysiphe quercicola
infecting the rubber tree (
Hevea brasiliensis
), causing latex yield losses. However, effectors of
E
.
quercicola
were rarely functionally characterized. In this study, we identified a highly specific candidate-secreted effector protein, EqCSEP04187, from
E
.
quercicola
. This putative effector is expressed at the late stage but not the early stage during infection. The constitutive expression of EqCSEP04187 in model plants
Nicotiana benthamiana
and
Arabidopsis thaliana
elicited defense responses, as did transient expression of EqCSEP04187 in protoplasts of
H
.
brasiliensis
. Introducing EqCSEP04187 into another
H
.
brasiliensis-
associated fungal pathogen,
Colletotrichum gloeosporioides
, inhibited
H
.
brasiliensis
infection, and infection by
E
.
quercicola
was decreased in the
A
.
thaliana eds1
mutant expressing EqCSEP04187. Further analysis suggests that these reductions in infection were the consequences of EqCSEP04187 eliciting defense responses. Our study suggests that this putative effector has elicitor activity that can improve plant resistance.
Heat resistance is a common characteristic of harpins, a class of proteins found in Gram-negative bacteria, which may be related to the stability of coiled-coil (CC) structure. The CC structure is a ...ubiquitous protein folding and assembly motif made of α-helices wrapping around each other forming a supercoil. Specifically, whether the stability of the CC structure near to N-terminus of four selected harpin proteins from Xanthomonas (hereafter referred to as Hpa1) would influence their characteristics of heat resistance was investigated. We used bioinformatics approach to predict the structure of Hpa1, used the performance of hypersensitive response (HR)-induction activity of Hpa1 and circular dichroism (CD) spectral analyses to detect the relationship between the stability of the CC structure of Hpa1 and heat resistance.
Each of four-selected Hpa1 has two α-helical regions with one in their N-terminus that could form CC structure, and the other in their C-terminus that could not. And the important amino acid residues involved in the CC motifs are located on helices present on the surface of these proteins, indicating they may engage in the formation of oligo mericaggregates, which may be responsible for HR elicitation by harpins and their high thermal stability. Increased or decreased the probability of forming a CC could either induce a stronger HR response or eliminate the ability to induce HR in tobacco after high temperature treatment. In addition, although the four Hpa1 mutants had little effect on the induction of HR by Hpa1, its thermal stability was significantly decreased. The α-helical content increased with increasing temperature, and the secondary structures of Hpa1 became almost entirely α-helices when the temperature reached 200 °C. Moreover, the stability of the CC structure near to N-terminus was found to be positively correlated with the heat resistance of Hpa1.
The stability of the CC structure might sever as an inner drive for mediating the heat resistance of harpin proteins. Our results offer a new insight into the interpretation of the mechanism involved in the heat resistance of harpin protein and provide a theoretical basis for further harpin function investigations and structure modifications.
Plasma membrane H
-ATPases (PMAs) play an important role in the pathogenicity of pathogenic fungi. Lipid droplets are important storage sites for neutral lipids in fungal conidia and hyphae and can ...be used by plant pathogenic fungi for infection. However, the relationship between plasma membrane H
-ATPase, lipid droplets and virulence remains unclear. Here, we characterized a plasma membrane H
-ATPase, CsPMA2, that plays a key role in lipid droplet formation, appresorial development and virulence in
. Deletion of
impaired
conidial size, conidial germination, appressorial development and virulence but did not affect hyphal growth. Δ
increased the sensitivity of
to phytic acid and oxalic acid. CsPMA2 was localized to lipids on the plasma membrane and intracellular membrane. Deletion of
significantly inhibited the accumulation of lipid droplets and significantly affected the contents of some species of lipids, including 12 species with decreased lipid contents and 3 species with increased lipid contents. Furthermore, low pH can inhibit
expression and lipid droplet accumulation. Overall, our data revealed that the plasma membrane H
-ATPase CsPMA2 is involved in the regulation of lipid droplet formation and affects appressorial development and virulence in
.
Powdery mildew infects a wide range of crops and economic plants, causing substantial losses. Rubber trees (
) are the primary source of natural rubber, and powdery mildew infection causes ...significant losses to natural rubber yields. How the causal agent,
, establishes successful infection in rubber trees is largely unknown. Previously, 133 candidate secreted effector proteins (CSEPs) were identified in powdery mildew fungus. In this study, we characterize a CSEP named EqCSEP01276 for its function in suppressing host plant defense responses. We show that EqCSEP01276 is a secreted protein and is able to disturb the localization of 9-
-epoxycarotenoid dioxygenase 5 (HbNCED5), a key enzyme in abscisic acid (ABA) biosynthesis in plant cell chloroplasts of
.
. We also show that this effector inhibits ABA biosynthesis, and that in
.
ABA is a positive regulator of the plant immune response against powdery mildew. Our study reveals a strategy by which powdery mildew fungus manipulates plant ABA-mediated defense for a successful infection.
Cotton Verticillium wilt is mainly caused by the fungus
, which threatens the production of cotton. Its pathogen can survive in the soil for several years in the form of microsclerotia, making it a ...destructive soil-borne disease. The accurate, sensitive, and rapid detection of
from complex soil samples is of great significance for the early warning and management of cotton Verticillium wilt. In this study, we combined the loop-mediated isothermal amplification (LAMP) with CRISPR/Cas12a technology to develop an accurate, sensitive, and rapid detection method for
. Initially, LAMP primers and CRISPR RNA (crRNA) were designed based on a specific DNA sequence of
, which was validated using several closely related
spp. The lower detection limit of the LAMP-CRISPR/Cas12a combined with the fluorescent visualization detection system is approximately ~10 fg/μL genomic DNA per reaction. When combined with crude DNA-extraction methods, it is possible to detect as few as two microsclerotia per gram of soil, with the total detection process taking less than 90 min. Furthermore, to improve the method's user and field friendliness, the field detection results were visualized using lateral flow strips (LFS). The LAMP-CRISPR/Cas12a-LFS system has a lower detection limit of ~1 fg/μL genomic DNA of the
, and when combined with the field crude DNA-extraction method, it can detect as few as six microsclerotia per gram of soil, with the total detection process taking less than 2 h. In summary, this study expands the application of LAMP-CRISPR/Cas12a nucleic acid detection in
and will contribute to the development of field-deployable diagnostic productions.
The genus
consists of obligate parasites that cause ring spot, scab, and leaf blight diseases in higher plant species. We assembled the three complete mitogenomes for the guava fruit ring spot ...pathogen,
. The mitogenomes are circular, with sizes of 38,666 bp, 33,846 bp, and 32,593 bp. The comparative analyses with
showed that
differs greatly from it in the length of the mitogenomes and the number of introns. Moreover, they showed significant differences in the gene content and tRNAs. The two genera showed little difference in gene skewness and codon preference for core protein-coding genes (PCGs). We compared gene sequencing in the mitogenomes of the order
and found large-scale gene rearrangement events, such as gene translocations and the duplication of tRNAs.
shows a unique evolutionary position in the phylum
constructed in phylogenetic analyses. We also found a more concentrated distribution of evolutionary pressures on the PCGs of
in the phylum
and that they are under little selective pressure compared to other species and are subjected to purifying selection. This study explores the evolutionary dynamics of the mitogenomes of
and provides important support for genetic and taxonomic studies.
Soft rot pectobacteria are devastating plant pathogens with a global distribution and a broad host range.
L6, previously isolated from leaves of
, is a pectolytic bacterial pathogen that causes ...typical soft rot on
. There is a shortage for genome data of
, which seriously hinders research on classification and pathogenesis of
. We present here the complete genome sequence of
L6. The L6 strain carries a single 4,995,896-bp chromosome with 53.10% G + C content and harbors 4,306 predicted protein-coding genes. We estimated
DNA-DNA hybridization and average nucleotide identity values in combination with the whole-genome-based phylogeny from 19
strains including
L6. The results showed that L6 and PC1 formed a population distinct from other populations of the
genus. Phylogenetic analysis based on 16S rRNA and genome sequences showed a close evolutionary relationship among
species. Overall, evolutionary analysis showed that L6 was in the same branch with PC1. In comparison with 18
spp. reference pathogens, strain L6 had 2,712 gene families, among which 1,632 gene families were identified as orthologous to those strains, as well as 1 putative unique gene family. We discovered 478 genes, 10.4% of the total of predicted genes, that were potentially related to pathogenesis using the Virulence Factors of Pathogenic Bacteria database. A total of 25 genes were related to toxins, 35 encoded plant cell-wall degrading enzymes, and 122 were involved in secretion systems. This study provides a foundation for a better understanding of the genomic structure of
and particularly offers information for the discovery of potential pathogenic factors and the development of more effective strategies against this pathogen.
Harpins, encoded by hrp (hypersensitive response and pathogenicity) genes of Gram-negative plant pathogens, are elicitors of hypersensitive response (HR). HpaXm is a novel harpin-like protein ...described from cotton leaf blight bacteria, Xanthomonas citri subsp. malvacearum-a synonym of X. campestris pv. malvacearum (Smith 1901-1978). A putative signal peptide (1-MNSLNTQIGANSSFL-15) of hpaXm was predicted in the nitroxyl-terminal (N-terminal)by SignalP (SignalP 3.0 server). Here, we explored the function of the N-terminal leader peptide like segment of hpaXm using transgenic tobacco (Nicotiana tabacum cv. Xanthi nc.). Transgenic tobacco lines expressing the full-length hpaXm and the signal peptide-like segment-deleted mutant hpaXmΔLP were developed using transformation mediated by Agrobacterium tumefaciens. The target genes were confirmed integrated into the tobacco genomes and expressed normally. Using immune colloidal-gold detection technique, hpaXm protein was found to be transferred to the cytoplasm, the cell membrane, and organelles such as chloroplasts, mitochondria, and nucleus, as well as the cell wall. However, the deletion mutant hpaXmΔLP expressed in transgenic tobacco was found unable to cross the membrane to reach the cell wall. Additionally, soluble proteins extracted from plants transformed with hpaXm and hpaXmΔLP were bio-active. Defensive micro-HR induced by the transgene expression of hpaXm and hpaXmΔLP were observed on transgenic tobacco leaves. Disease resistance bioassays to tobacco mosaic virus (TMV) showed that tobacco plants transformed with hpaXm and with hpaXmΔLP exhibited enhanced resistance to TMV. In summary, the N-terminal signal peptide-like segment (1-45 bp) in hpaXm sequence is not necessary for transgene expression, bioactivity of hpaXm and resistance to TMV in transgenic tobacco, but is required for the protein to be translocated to the cell wall.
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