Transcription factors VviWRKY10 and VviWRKY30 co-regulate powdery mildew resistance in grapevine

Grapevine (Vitis vinifera) is an economically important fruit crop worldwide. The widely cultivated grapevine is susceptible to powdery mildew caused by Erysiphe necator. In this study, we used CRISPR-Cas9 to simultaneously knock out VviWRKY10 and VviWRKY30 encoding two transcription factors reported to be implicated in defense regulation. We generated 53 wrky10 single mutant transgenic plants and 15 wrky10 wrky30 double mutant transgenic plants. In a 2-yr field evaluation of powdery mildew resistance, the wrky10 mutants showed strong resistance, while the wrky10 wrky30 double mutants showed moderate resistance. Further analyses revealed that salicylic acid (SA) and reactive oxygen species contents in the leaves of wrky10 and wrky10 wrky30 were substantially increased, as was the ethylene (ET) content in the leaves of wrky10. The results from dual luciferase reporter assays, electrophoretic mobility shift assays and chromatin immunoprecipitation (ChIP) assays demonstrated that VviWRKY10 could directly bind to the W-boxes in the promoter of SA-related defense genes and inhibit their transcription, supporting its role as a negative regulator of SA-dependent defense. By contrast, VviWRKY30 could directly bind to the W-boxes in the promoter of ET-related defense genes and promote their transcription, playing a positive role in ET production and ET-dependent defense. Moreover, VviWRKY10 and VviWRKY30 can bind to each other's promoters and mutually inhibit each other's transcription. Taken together, our results reveal a complex mechanism of regulation by VviWRKY10 and VviWRKY30 for activation of measured and balanced defense responses against powdery mildew in grapevine.

Genome-wide identification of the CYP82 gene family in cucumber and functional characterization of CsCYP82D102 in regulating resistance to powdery mildew

The cytochrome P450 (CYP450) gene family plays a vital role in basic metabolism, hormone signaling, and enhances plant resistance to stress. Among them, the CYP82 gene family is primarily found in dicots, and they are typically activated in response to various specific environmental stresses. Nevertheless, their roles remain considerably obscure, particularly within the context of cucumber. In the present study, 12 CYP82 subfamily genes were identified in the cucumber genome. Bioinformatics analysis included gene structure, conserved motif, cis-acting promoter element, and so on. Subcellular localization predicted that all CYP82 genes were located in the endoplasmic reticulum. The results of cis element analysis showed that CYP82s may significantly affect the response to stress, hormones, and light exposure. Expression patterns of the CYP82 genes were characterized by mining available RNA-seq data followed by qRT-PCR (quantitative real-time polymerase chain reaction) analysis. Members of CYP82 genes display specific expression profiles in different tissues, and in response to PM and abiotic stresses in this study, the role of CsCYP82D102, a member of the CYP82 gene family, was investigated. The upregulation of CsCYP82D102 expression in response to powdery mildew (PM) infection and treatment with methyl jasmonate (MeJA) or salicylic acid (SA) was demonstrated. Further research found that transgenic cucumber plants overexpressing CsCYP82D102 display heightened resistance against PM. Wild-type (WT) leaves exhibited average lesion areas of approximately 29.7% at 7 dpi upon powdery mildew inoculation. In contrast, the two independent CsCYP82D102 overexpression lines (OE#1 and OE#3) displayed significantly reduced necrotic areas, with average lesion areas of approximately 13.4% and 5.7%. Additionally, this enhanced resistance is associated with elevated expression of genes related to the SA/MeJA signaling pathway in transgenic cucumber plants. This study provides a theoretical basis for further research on the biological functions of the P450 gene in cucumber plants.

Phylogeny and taxonomy of the genera of Erysiphaceae, part 5: Erysiphe (the "Microsphaera lineage" part 1)

In this contribution, we offer the fifth installment of a series focusing on the phylogeny and taxonomy of powdery mildews. This paper is the second segment evaluating the genus Erysiphe. The first treatment of Erysiphe focused on phylogenetically basal species in the "Uncinula lineage." This research presents a phylogenetic-taxonomic assessment of species that form the group previously referred to as the "Microsphaera lineage." Given the size of the group, we split the treatment of this lineage of Erysiphe species into two parts based on their phylogenetic placement. Phylogenetic trees based on ITS+28S data are supplemented by sequences of additional markers (CAM, GADPH, GS, RPB2, and TUB). Included in the analysis of the Microsphaera lineage is the "Erysiphe aquilegiae complex" (group, clade, cluster), which encompasses sequences obtained from an assemblage of Erysiphe species with insufficient resolution in rDNA analyses. Attempts have been made to resolve this group at the species level by applying a multilocus approach. A detailed discussion of the "Erysiphe aquilegiae complex" is provided. Sequences are provided for the first time for several species, particularly North American species, such as Erysiphe aggregata, E. erineophila, E. parnassiae, and E. semitosta. Ex-type sequences for Microsphaera benzoin and M. magnusii have been retrieved. Alphitomorpha penicillata, Microsphaera vanbruntiana, and M. symphoricarpi are epitypified with ex-epitype sequences. The new species Erysiphe alnicola, E. deutziana, E. cornigena, E. lentaginis, and E. sambucina are described, the new combinations E. lauracearum, E. passiflorae, and E. sambucicola are introduced, and the new name E. santali is proposed.

Genetic Analysis and Molecular Identification of the Powdery Mildew Resistance in 116 Elite Wheat Cultivars/Lines

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a destructive disease worldwide. Host resistance is the preferred method for limiting the disease epidemic, protecting the environment, and minimizing economic losses. In the present study, the reactions to powdery mildew for a collection of 600 wheat cultivars and breeding lines from different wheat-growing regions were tested using the Bgt isolate E09. Next, 116 resistant genotypes were identified and then crossed with susceptible wheat cultivars/lines to produce segregating populations for genetic analysis. Among them, 87, 19, and 10 genotypes displayed single, dual, and multiple genic inheritance, respectively. To identify the Pm gene(s) in those resistant genotypes, 16 molecular markers for 13 documented Pm genes were used to test the resistant and susceptible parents and their segregating populations. Of the 87 wheat genotypes that fitted the monogenic inheritance, 75 carried the Pm2a allele. Three, two, one, and two genotypes carried Pm21, Pm6, Pm4, and the recessive genes pm6 and pm42, respectively. Four genotypes did not carry any of the tested genes, suggesting that they might have other uncharacterized or new genes. The other 29 wheat cultivars/lines carried two or more of the tested Pm genes and/or other untested genes, including Pm2, Pm5, Pm6, and/or pm42. It was obvious that Pm2 was widely used in wheat production, whereas Pm1, Pm24, Pm33, Pm34, Pm35, Pm45, and Pm47 were not detected in any of these resistant wheat genotypes. This study clarified the genetic basis of the powdery mildew resistance of these wheat cultivars/lines to provide information for their rational utilization in different wheat-growing regions. Moreover, some wheat genotypes which may have novel Pm gene(s) were mined to enrich the diversity of resistance source.

Genetic Mapping of a Novel Gene PmAege7M from Aegilops geniculata Conferring Resistance to Wheat Powdery Mildew

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is one of the most damaging foliage diseases of wheat across the world. Aegilops geniculata Roth is a valuable gene resource for enhancing wheat resistance to powdery mildew. This study identified Ae. geniculata accession PI 487224 as immune and PI 487228 as susceptible to powdery mildew. Genetic analysis of the F1, F2, and F2:3 progeny derived from PI 487224 × PI 487228 showed that powdery mildew resistance in PI 487224 was controlled by two independent dominant genes located on two different nonhomologous chromosomes. By combing bulked segregant RNA-Seq, genetic linkage analysis of a single resistance gene segregation population, and marker analysis of a set of 14 wheat-Ae. geniculata chromosome addition lines, one of the resistance genes, temperately designated PmAege7M, was mapped to a 4.9-cM interval flanked by markers STS7-55926 and SNP7-45792/STS7-65911 on the long arm of chromosome 7 Mg of PI 487224, spanning 604.73 to 622.82 Mb on the 7D long arm based on the Ae. tauschii reference genome (Aet_v4.0). The map and closely linked markers of PmAege7M from Ae. geniculata in this study will facilitate the transfer of PmAege7M into common wheat and fine mapping of the gene.

Development and Identification of a Wheat-Rye Breeding Line for Harmonious Improvement Between Powdery Mildew Resistance and High Yield Potential

Powdery mildew, caused by Blumeria graminis f. sp. tritici, is a devastating disease that seriously threatens wheat yield and quality. To control this disease, host resistance is the preferred measure. However, wheat breeding is a complex process with elusive exchange and recombination of the traits from their parents. Increased resistance often leads to a decline in other key traits, such as yield and quality. Developing breakthrough germplasms with harmonious powdery mildew resistance and other key breeding traits is attractive in wheat breeding. In this study, we developed an ideal wheat breeding line AL46 that pyramided its hexaploid triticale parent-derived desirable yield traits and its wheat parent-derived powdery mildew resistance gene Pm2. Sequential genomic in situ hybridization (GISH), multicolor GISH, multicolor fluorescence in situ hybridization, and molecular marker analyses revealed that AL46 was a wheat-rye T1RS·1BL translocation line. Genetic analysis combined with function marker detection and sequence alignment were used to confirm that AL46 carried the Pm2 gene. Then, we evaluated the powdery mildew resistance and comprehensive traits of AL46, and just as we designed, AL46 showed harmonious powdery mildew resistance with some key breeding traits. This study not only developed an ideal wheat germplasm resource but also provided a successful example for pyramiding breeding, which could be a promising direction for wheat improvement in the future.

Resistance to Powdery Mildew Is Conferred by Different Genetic Loci at the Adult-Plant and Seedling Stages in Winter Wheat Line Tianmin 668

Winter wheat line Tianmin 668 was crossed with susceptible cultivar Jingshuang 16 to develop 216 recombinant inbred lines (RILs) for dissecting its adult-plant resistance (APR) and all-stage resistance (ASR) against powdery mildew. The RIL population was genotyped on a 16K genotyping by target sequencing single-nucleotide polymorphism array and phenotyped in six field trials and in the greenhouse. Three loci-QPmtj.caas-2BL, QPmtj.caas-2AS, and QPmtj.caas-5AL-conferring APR to powdery mildew were detected on chromosomes 2BL, 2AS, and 5AL, respectively, of Tianmin 668. The effect of resistance to powdery mildew for QPmtj.caas-2BL was greater than that of the other two loci. A Kompetitive allele-specific PCR marker specific for QPmtj.caas-2BL was developed and verified on 402 wheat cultivars or breeding lines. Results of virulence and avirulence patterns to 17 Blumeria graminis f. sp. tritici isolates, bulked segregant analysis-RNA-sequencing, and a genetic linkage mapping identified a resistance allele at locus Pm4 in Tianmin 668 based on the seedling phenotypes of the RIL population. The PCR-based DNA sequence alignment and cosegregation of the functional marker with the phenotypes of the RIL population demonstrated that Pm4d was responsible for the ASR to isolate Bgt1 in Tianmin 668. The dissection of genetic loci for APR and ASR may facilitate the application of Tianmin 668 in developing powdery mildew-resistant wheat cultivars.

Identification of a Wheat Powdery Mildew Dominant Resistance Gene in the Pm5 Locus for High-Throughput Marker-Assisted Selection

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), poses a severe threat to wheat yield and quality worldwide. Rapid identification and the accurate transference of effective resistance genes are important to the development of resistant cultivars and the sustainable control of this disease. In the present study, the wheat line AL11 exhibited high levels of resistance to powdery mildew at both the seedling and adult plant stages. Genetic analysis of the AL11 × 'Shixin 733' mapping population revealed that its resistance was controlled by a single dominant gene, tentatively designated PmAL11. Using bulked segregant RNA-Seq and molecular marker analysis, PmAL11 was mapped to the Pm5 locus on chromosome 7B where it cosegregated with the functional marker Pm5e-KASP. Sequence alignment analysis revealed that the Pm5e-homologous sequence in AL11 was identical to the reported recessive gene Pm5e in wheat landrace 'Fuzhuang 30'. It appears that PmAL11 was most probably Pm5e, but it was mediated by a dominant inheritance pattern, so it should provide a valuable resistance resource for both genetic study and wheat breeding. To efficiently use and trace PmAL11 in breeding, a new kompetitive allele-specific PCR marker AL11-K2488 that cosegregated with this gene was developed and confirmed to be applicable in the different wheat backgrounds, thus promoting its use in the marker-assisted selection of PmAL11.

Comparative proteomic analysis reveals molecular differences between incompatible and compatible interaction of Erysiphe pisi in garden pea

Comparative proteome analysis of Erysiphe pisi-infected pea genotypes; JI-2480 carrying er2 resistant gene and Arkel, the susceptible genotype by liquid chromatography- mass spectrometry (LCMS/MS QTOF) at 72 h post inoculation (hpi) revealed several differentially abundant proteins (DAPs) of both the host and the pathogen. The functional annotation of proteins through gene enrichment and KEGG pathway analyses revealed strong up-regulation of pathogenesis related protein NPR1, proteins related to defense, transportation and signal transduction, hypersensitive response, cell wall modifications, phenylpropanoid and metabolic pathways in J-72. Significant abundance of membrane-related polypeptides, kinase domains and small GTPase signal transduction-related proteins suggested their major role in plant defense. The abundance of cellular antioxidant protein, catalase and its isozyme along with calreticulin-1 and 2 in J-72 confirmed their intervention in maintaining a redox balance in powdery mildew defense. High abundance levels of Glycolysis-related proteins indicated it as a major pathway for energy source during fungal growth. The majority of pathogenicity and virulence genes were downregulated in J-72 compared to A-72, while four EKA (Effectors homologues to Avk1 and Avra10) like avirulence proteins were significantly upregulated in incompatible interaction suggesting their role in eliciting hypersensitive response in pea against E. pisi.