Generation of β-glucuronidase reporter-tagged strain to monitor Ustilaginoidea virens infection in rice

Cloning and functional verification of the CmHSP17.9 gene from chrysanthemum

Small molecular heat shock proteins (sHSPs) belong to the HSP family of molecular chaperones. Under high-temperature stress, they can prevent the aggregation of irreversible proteins and maintain the folding of denatured proteins to enhance heat resistance. In this study, the CmHSP17.9-1 and CmHSP17.9-2 genes, which were cloned from chrysanthemum (Chrysanthemum×morifolium 'Jinba') by homologous cloning, had a complete open reading frame of 480 bp each, encoding 159 amino acids. The protein subcellular localization analysis showed that CmHSP17.9-1 and CmHSP17.9-2 were located in the cytoplasm and mostly aggregated in granules, especially around the nucleus. Real-time quantitative PCR (qRT-PCR) analysis showed that the relative expression level of the CmHSP17.9-1 and CmHSP17.9-2 genes was highest in the terminal buds of the chrysanthemum, followed by the leaves. CmHSP17.9-1 and CmHSP17.9-2 overex-pression vectors were constructed and used to transform the chrysanthemum; overexpression of these genes led to the chrysanthemum phenotypes being less affected by high-temperature, and the antioxidant capacity was enhanced. The results showed that chrysanthemum with overex-pression of the CmHSP17.9-1 and CmHSP17.9-2 genes had stronger tolerance than the wild type chrysanthemum after high-temperature treatment or some degree of heat exercise, and overex-pression of the CmHSP17.9-1 gene led to stronger heat resistance than that of the CmHSP17.9-2 gene, providing an important theoretical basis for the subsequent molecular breeding and pro-duction applications of chrysanthemum.

Grain Characteristics, Moisture, and Specific Peptides Produced by Ustilaginoidea virens Contribute to False Smut Disease in Rice (Oryza sativa L.)

The fungus Ustilaginoidea virens, the causative agent of false smut in rice (Oryza sativa L.), is responsible for one of the severe grain diseases that lead to significant losses worldwide. In this research, microscopic and proteomic analyses were performed by comparing U. virens infected and non-infected grains of the susceptible and resistant rice varieties to provide insights into the molecular and ultrastructural factors involved in false smut formation. Prominent differentially expressed peptide bands and spots were detected due to false smut formation as revealed by sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional gel electrophoresis (2-DE) SDS-PAGE profiles and were identified using liquid chromatography-mass spectrometry (LC-MS/MS). The proteins identified from the resistant grains were involved in diverse biological processes such as cell redox homeostasis, energy, stress tolerance, enzymatic activities, and metabolic pathways. It was found that U. virens produces diverse degrading enzymes such as β-1, 3-endoglucanase, subtilisin-like protease, putative nuclease S1, transaldolase, putative palmitoyl-protein thioesterase, adenosine kinase, and DNase 1 that could discretely alter the host morphophysiology resulting in false smut. The fungus also produced superoxide dismutase, small secreted proteins, and peroxidases during the smut formation. This study revealed that the dimension of rice grain spikes, their elemental composition, moisture content, and the specific peptides produced by the grains and the fungi U. virens play a vital role in the formation of false smut.

Establishment of Agrobacterium tumefaciens - mediated genetic transformation of apple pathogen Marssonina coronaria using marker genes under the control of CaMV 35S promoter

Premature leaf fall of apple caused by Marssonina coronaria is economically very important apple disease and all the commercially available apple cultivars are susceptible to this disease. The non-availability of an efficient transformation system for this fungus hinders the functional genomics research. Herein, we report for the first time, the successful Agrobacterium-mediated transformation in apple leaf blotch fungus M. coronaria by transferring T-DNA harbouring the genes for hygromycin phosphotransferase (hpt), β-glucuronidase (uidA) and green fluorescent protein (gfp) under the control of CaMV 35S promoter. The key factors that affect the transformation efficiency including type of recipient fungal material, acetosyringone concentration, the conditions for co-cultivation, Agrobacterium concentration, Agrobacterium strains and membrane types as support were investigated. The present results have recommended that 250 μM concentration of acetosyringone, 24 °C temperature and 48 h time, 0.5 OD₆₀₀ of A. tumefaciens, EHA105 Agrobacterium strain and Whatman filter paper were the optimal co-cultivation conditions for the transformation of M. coronaria by using fragmented mycelia suspension and mycelial plugs. We observed that conidia were tedious to transform as compared to the fragmented mycelia and mycelial plugs of this slow growing fungus. These optimized parameters yielded 54 and 70 average transformants per 60 mycelial plugs and 10⁴ fragmented mycelia, respectively. Fungal transformants were analysed for T-DNA integration, gus gene expression and gfp gene expression. Strong gus histochemical staining and green fluorescence expression indicated that the CaMV 35S promoter can drive gene expression in M. croronaria. Some mutants showed difference in the morphology of the colony as compared to the wild type control. This report will be very useful to inspect molecular basis of apple-M. coronaria interactions by deciphering the functional roles of various genes in this pathogenic fungus.