Silencing of the Wheat Protein Phosphatase 2A Catalytic Subunit TaPP2Ac Enhances Host Resistance to the Necrotrophic Pathogen Rhizoctonia cerealis

Eukaryotic type 2A protein phosphatases (protein phosphatase 2A, PP2A) consist of a scaffold subunit A, a regulatory subunit B, and a catalytic subunit C. Little is known about the roles of PP2Ac proteins that are involved in plant responses to necrotrophic fungal pathogens. Sharp eyespot, caused by the necrotrophic fungus Rhizoctonia cerealis, is a destructive disease of wheat (Triticum aestivum), an important staple food crop. Here, we isolated TaPP2Ac-4D from wheat, which encodes a catalytic subunit of the heterotrimeric PP2A, and characterized its properties and role in plant defense response to R. cerealis. Based on the sequence alignment of TaPP2Ac-4D with the draft sequences of wheat chromosomes from the International Wheat Genome Sequencing Consortium (IWGSC), it was found that TaPP2Ac-4D gene is located on the long arm of the wheat chromosome 4D and has two homologs assigned on wheat chromosomes 4A and 4B. Sequence and phylogenetic tree analyses revealed that the TaPP2Ac protein is a typical member of the PP2Ac family and belongs to the subfamily II. TaPP2Ac-4B and TaPP2Ac-4D displayed higher transcriptional levels in the R. cerealis-susceptible wheat cultivar Wenmai 6 than those seen in the resistant wheat line CI12633. The transcriptional levels of TaPP2Ac-4B and TaPP2Ac-4D were significantly elevated in wheat R. cerealis after infection and upon H2O2 treatment. Virus-induced gene silencing results revealed that the transcriptional knockdown of TaPP2Ac-4D and TaPP2Ac-4B significantly increased wheat resistance to R. cerealis infection. Meanwhile, the transcriptional levels of certain pathogenesis-related (PR) and reactive oxygen species (ROS)-scavenging enzyme encoding genes were increased in TaPP2Ac-silenced wheat plants. These results suggest that TaPP2Ac-4B and TaPP2Ac-4D negatively regulate defense response to R. cerealis infection possibly through modulation of the expression of certain PR and ROS-scavenging enzyme genes in wheat. This study reveals a novel function of the plant PP2Ac genes in plant immune responses

Robust ferromagnetism of single crystalline CoxZn1−xO (0.3 ≤ x ≤ 0.45) epitaxial films with high Co concentration

In contrast to conventional dilute magnetic semiconductors with concentrations of magnetic ions of just a few percent, here, we report the fabrication of epitaxial Cox Zn 1− xO single crystalline films with Co concentrations from x = 0.3 up to 0.45 by radio-frequency oxygen-plasma-assisted molecular beam epitaxy. The films retain their single crystalline wurtzite structure without any other crystallographic phase from precipitates, based on reflection high energy electron diffraction, X-ray diffraction, transmission electron microscopy, and Raman scattering. The results of X-ray diffraction, optical transmission spectroscopy, and in-situ X-ray photoelectron spectroscopy confirm the incorporation of Co2+ cations into the wurtzite lattice. The films exhibit robust ferromagnetism and the magneto-optical Kerr effect at room temperature. The saturation magnetization reaches 265 emu/cm3 at x = 0.45, which corresponds to the average magnetic moment of 1.5 μB per Co atom

The wheat LLM-domain-containing transcription factor TaGATA1 positively modulates host immune response to Rhizoctonia cerealis

Wheat (Triticumaestivum) is essential for global food security. Rhizoctonia cerealis is the causal pathogen of sharp eyespot, an important disease of wheat. GATA proteins in model plants have been implicated in growth and development; however, little is known about their roles in immunity. Here, we reported a defence role of a wheat LLM-domain-containing B-GATA transcription factor, TaGATA1, against R. cerealis infection and explored the underlying mechanism. Through transcriptomic analysis, TaGATA1 was identified to be more highly expressed in resistant wheat genotypes than in susceptible wheat genotypes. TaGATA1 was located on chromosome 3B and had two homoeologous genes on chromosomes 3A and 3D. TaGATA1 was demonstrated to localize in the nucleus, possess transcriptional-activation activity, and bind to GATA-core cis-elements. TaGATA1 overexpression significantly enhanced resistance of transgenic wheat to R. cerealis, whereas silencing of TaGATA1 suppressed the resistance. RT-qPCR and chromatin immunoprecipitation-qPCR results indicated that TaGATA1 directly bound to and activated certain defence genes in host immune response to R. cerealis. Collectively, TaGATA1 positively regulates immune responses to R. cerealis through activating expression of defence genes in wheat. This study reveals a new function of plant GATAs in immunity and provides a candidate gene for improving crop resistance to R. cerealis

The Wall-Associated Receptor-Like Kinase TaWAK7D Is Required for Defense Responses to Rhizoctonia cerealis in Wheat

Sharp eyespot, caused by necrotrophic fungus Rhizoctonia cerealis, is a serious fungal disease in wheat (Triticum aestivum). Certain wall-associated receptor kinases (WAK) mediate resistance to diseases caused by biotrophic/hemibiotrophic pathogens in several plant species. Yet, none of wheat WAK genes with positive effect on the innate immune responses to R. cerealis has been reported. In this study, we identified a WAK gene TaWAK7D, located on chromosome 7D, and showed its positive regulatory role in the defense response to R. cerealis infection in wheat. RNA-seq and qRT-PCR analyses showed that TaWAK7D transcript abundance was elevated in wheat after R. cerealis inoculation and the induction in the stem was the highest among the tested organs. Additionally, TaWAK7D transcript levels were significantly elevated by pectin and chitin treatments. The knock-down of TaWAK7D transcript impaired resistance to R. cerealis and repressed the expression of five pathogenesis-related genes in wheat. The green fluorescent protein signal distribution assays indicated that TaWAK7D localized on the plasma membrane in wheat protoplasts. Thus, TaWAK7D, which is induced by R. cerealis, pectin and chitin stimuli, positively participates in defense responses to R. cerealis through modulating the expression of several pathogenesis-related genes in wheat

Genome-Wide Identification of M35 Family Metalloproteases in Rhizoctonia cerealis and Functional Analysis of RcMEP2 as a Virulence Factor during the Fungal Infection to Wheat

Rhizoctonia cerealis is the causal pathogen of the devastating disease, sharp eyespot, of the important crop wheat (Triticum aestivum L.). In phytopathogenic fungi, several M36 metalloproteases have been implicated in virulence, but pathogenesis roles of M35 family metalloproteases are largely unknown. Here, we identified four M35 family metalloproteases from R. cerealis genome, designated RcMEP2–RcMEP5, measured their transcriptional profiles, and investigated RcMEP2 function. RcMEP2-RcMEP5 are predicted as secreted metalloproteases since each protein sequence contains a signal peptide and an M35 domain that includes two characteristic motifs HEXXE and GTXDXXYG. Transcription levels of RcMEP2-RcMEP5 markedly elevated during the fungus infection to wheat, among which RcMEP2 expressed with the highest level. Functional dissection indicated that RcMEP2 and its M35 domain could trigger H2O2 rapidly-excessive accumulation, induce cell death, and inhibit expression of host chitinases. This consequently enhanced the susceptibility of wheat to R. cerealis and the predicated signal peptide of RcMEP2 functions required for secretion and cell death-induction. These results demonstrate that RcMEP2 is a virulence factor and that its M35 domain and signal peptide are necessary for the virulence role of RcMEP2. This study facilitates a better understanding of the pathogenesis mechanism of metalloproteases in phytopathogens including R. cerealis

TaWAK2A-800, a Wall-Associated Kinase, Participates Positively in Resistance to Fusarium Head Blight and Sharp Eyespot in Wheat

Fusarium head blight (FHB) and sharp eyespot are important diseases of the cereal plants, including bread wheat (Triticum aestivum) and barley. Both diseases are predominately caused by the pathogenic fungi, Fusarium graminearum and Rhizoctonia cerealis. The roles of the wheat-wall-associated kinases (WAKs) in defense against both F. graminearum and R. cerealis have remained largely unknown. This research reports the identification of TaWAK2A-800, a wheat WAK-coding gene located on chromosome 2A, and its functional roles in wheat resistance responses to FHB and sharp eyespot. TaWAK2A-800 transcript abundance was elevated by the early infection of R. cerealis and F. graminearum, or treatment with exogenous chitin. The gene transcript seemed to correspond to the resistance of wheat. Further functional analyses showed that silencing TaWAK2A-800 compromised the resistance of wheat to both FHB (F. graminearum) and sharp eyespot (R. cerealis). Moreover, the silencing reduced the expression levels of six defense-related genes, including the chitin-triggering immune pathway-marker genes, TaCERK1, TaRLCK1B, and TaMPK3. Summarily, TaWAK2A-800 participates positively in the resistance responses to both F. graminearum and R. cerealis, possibly through a chitin-induced pathway in wheat. TaWAK2A-800 will be useful for breeding wheat varieties with resistance to both FHB and sharp eyespot