Flavonoids Modulate the Accumulation of Toxins From Aspergillus flavus in Maize Kernels

Aspergillus flavus is an opportunistic fungal pathogen capable of producing aflatoxins, potent carcinogenic toxins that accumulate in maize kernels after infection. To better understand the molecular mechanisms of maize resistance to A. flavus growth and aflatoxin accumulation, we performed a high-throughput transcriptomic study in situ using maize kernels infected with A. flavus strain 3357. Three maize lines were evaluated: aflatoxin-contamination resistant line TZAR102, semi-resistant MI82, and susceptible line Va35. A modified genotype-environment association method (GEA) used to detect loci under selection via redundancy analysis (RDA) was used with the transcriptomic data to detect genes significantly influenced by maize line, fungal treatment, and duration of infection. Gene ontology enrichment analysis of genes highly expressed in infected kernels identified molecular pathways associated with defense responses to fungi and other microbes such as production of pathogenesis-related (PR) proteins and lipid bilayer formation. To further identify novel genes of interest, we incorporated genomic and phenotypic field data from a genome wide association analysis with gene expression data, allowing us to detect significantly expressed quantitative trait loci (eQTL). These results identified significant association between flavonoid biosynthetic pathway genes and infection by A. flavus. In planta fungal infections showed that the resistant line, TZAR102, has a higher fold increase of the metabolites naringenin and luteolin than the susceptible line, Va35, when comparing untreated and fungal infected plants. These results suggest flavonoids contribute to plant resistance mechanisms against aflatoxin contamination through modulation of toxin accumulation in maize kernels.

105 The Epigenetics and Plasticity of CD4+ T Cells in Poultry Health

Marek’s disease (MD) is one of the top priority diseases in chicken. The mechanisms through which immune cells react to virus infection and pathway signals represent the fundamental cell biological question to defeat MD. We hypothesized epigenetic status in immune organs and cells is directly associated with how the Marek’s disease virus (MDV) infection influences intrinsic transcriptional and regulatory networks in MD. To investigate the epigenetics in CD4+ T cells induced by MDV infection, we assembled a multifaceted approach with epigenetics, deep sequencing, and computational methods together to explore the roles of epigenetics in unique inbred lines of chickens. First, a genome-wide transcriptome analysis in the immune organs from resistant line 63 and susceptible line 72 chickens was performed to explore disease resistance mechanisms. MDV infection influences both cytokine-cytokine receptor interaction and cellular development in resistant and susceptible chickens. Second, we examined the epigenetic status of CD4+ T cells induced by MDV infection, including DNA methylations, histone modifications, chromatin accessibility, and 3D chromatin structures. Our results revealed more than 5,000 epigenetic modification changes (FDR< 0.01) and methylation changes (>15,000, FDR< 0.01) caused by MDV infection. Only resistant line 63 chickens could initiate robust adaptive immune responses at the transcription level (>200 genes, FDR< 0.05). The increase in chromatin accessibility (P < 0.001) and chromosome reorganization represented by A/B compartment flipping were related to up-regulated genes induced by MDV infection ten days post-infection in line 63 chickens. Our findings provided a deeper insight into the CD4+ T cell commitment and responses toward viral infection. In particular, the identifications of cis-acting and trans-acting regulations and lipid pathways will improve our understanding of the sequence, structural basis of RNA-protein, and RNA-DNA interactions and serve as the impetus for mechanistic studies to refine the genomic and epigenetic control of MD resistance in poultry.

Uncovering the transcriptional response of popcorn (Zea mays L. var. everta) under long-term aluminum toxicity

To date, the investigation of genes involved in Al resistance has focused mainly on microarrays and short periods of Al exposure. We investigated genes involved in the global response under Al stress by tracking the expression profile of two inbred popcorn lines with different Al sensitivity during 72 h of Al stress. A total of 1003 differentially expressed genes were identified in the Al-sensitive line, and 1751 were identified in the Al-resistant line, of which 273 were shared in both lines. Genes in the category of “response to abiotic stress” were present in both lines, but there was a higher number in the Al-resistant line. Transcription factors, genes involved in fatty acid biosynthesis, and genes involved in cell wall modifications were also detected. In the Al-resistant line, GST6 was identified as one of the key hub genes by co-expression network analysis, and ABC6 may play a role in the downstream regulation of CASP-like 5. In addition, we suggest a class of SWEET transporters that might be involved in the regulation of vacuolar sugar storage and may serve as mechanisms for Al resistance. The results and conclusions expand our understanding of the complex mechanisms involved in Al toxicity and provide a platform for future functional analyses and genomic studies of Al stress in popcorn.

Functional Analysis of A Soybean Ferredoxin-NADP Reductase (FNR) Gene in Response to Soybean Mosaic Virus

The Ferredoxin-NADP reductase (FNR) gene plays a significant role in NADPH production, carbon assimilation, antioxidation, and cross-talking between chloroplasts and mitochondria in plants. This study aims to know the functional response of the soybean FNR gene (GmFNR) during a soybean mosaic virus (SMV) infection. For this purpose, we developed the bean pod mottle virus (BPMV)-based gene construct (BPMV-GmFNR) and used it to silence the GmFNR gene in resistant and susceptible lines. The results showed that GmFNR expression decreased to 50% in the susceptible line, compared to 40% in the resistant line. The silencing of GmFNR reduces the photosynthetic capacity and CAT activity of both lines compared to their respective controls. In addition, the H2O2 content increased significantly in the susceptible line, whereas the resistant line did not exhibit any change. Further, an SMV infection in the silencing plants of the susceptible line resulted in serious morphological changes and increased the SMV NIa-protease transcript accumulation compared to its control plants. However, the same impact was not observed in the resistant line. The yeast two-hybrid system, BIFC assay, and quantitative real-time polymerase chain reaction (qRT-PCR) analyses revealed that the GmFNR was interacting with EF1A and coincided with the increased SMV accumulation. The results obtained in this study improve the understanding of the soybean FNR gene response during SMV infection and provide a novel insight into the SMV resistance mechanism.

Comparative transcriptome profiling and co-expression network analysis uncover the key genes associated withearly-stage resistance to Aspergillus flavus in maize

Background The fungus Aspergillus flavus (A. flavus) is a serious threat to maize (Zea mays) production worldwide. It causes considerable yield and economic losses, and poses a health risk to humans and livestock due to the high toxicity of aflatoxin. However, key genes and regulatory networks conferring maize resistance to A. flavus are not clear, especially at the early stage of infection. Here, we performed a comprehensive transcriptome analysis of two maize inbred lines with contrasting resistance to A. flavus infection. Results The pairwise comparisons between mock and infected kernels in each line during the first 6 h post inoculation (hpi) showed that maize resistance to A. flavus infection was specific to the genotype and infection stage, and defense pathways were strengthened in the resistant line. Further comparison of the two maize lines revealed that the infection-induced up-regulated differentially expressed genes (DEGs) in the resistant line might underlie the enhanced resistance. Gene co-expression network analysis by WGCNA (weighted gene co-expression network analysis) identified 7 modules that were significantly associated with different infection stages, and 110 hub genes of these modules. These key regulators mainly participate in the biosynthesis of fatty acid and antibiotics. In addition, 90 candidate genes for maize resistance to A. flavus infection and/or aflatoxin contamination obtained in previous studies were confirmed to be differentially expressed between the resistant and susceptible lines within the first 6 hpi. Conclusion This work unveiled more A. flavus resistance genes and provided a detailed regulatory network of early-stage resistance to A. flavus in maize.

Biosorptio Of Cd2+ By Wildtype And Cadmium Resistant, CdR-99 Cell Line Of Chlorella Vulgaris

Removal of heavy metals is very important in wastewater treatment process, due to their toxic effects on the environment. Biological treatment has attracted researchers for years since it has many advantages over physical and chemical methods for removing heavy metals from wastewater. The purpose of this research was to assess the biosorption of Cd2+ by wildtype (WT) and CdR-99 resistant line of Chlorella vulgaris confirming mechanisms of resistance to Cd2+ toxicity and the effect of the variable concentrations of Cd2+ on their growth. Exposure of both algal cell lines to increasing Cd2+ concentrations resulted in progressive inhibition of growth as revealed by growth experiments. The higher ID50 value (38 μM Cd2+) of CdR-99 resistant line exhibited some degree of resistance to Cd2+ toxicity. Metal content was determined by flame atomic absorption spectrometry (FAAS). When exposed to the growth medium containing 50 μM Cd2+, CdR-99 resistant isolate proved to be efficient cell line compared to the WT, in terms of adsorption and removal of Cd2+ at 15 min and 48 hr interval of time respectively. Extracellular Cd2+ adsorption was found significantly higher than intracellular uptake in both the tested cell lines. Total Cd2+ accumulation and distribution between the external and internal cell fractions of the CdR-99 were significantly higher to the WT. Thus, the CdR-99 cell line appeared more resistant to Cd2+ toxicity and hence may be used for wastewater treatment and remediation of metal contaminated sites.

Glucosinolate profile and Myrosinase gene expression are modulated upon Plasmodiophora brassicae infection in cabbage

Clubroot is a devastating disease of Brassicaceae caused by the biotrophic protist Plasmodiophora brassicae. The progression of clubroot disease is modulated by the glucosinolate (GSL) profile of the host plant. GSL is hydrolysed by the enzyme myrosinase upon cell disruption and gives rise to metabolites like isothiocyanate, nitriles, thiocyanates, epithionitriles and oxazolidines. Some of these metabolites play important roles in the plant’s defence mechanism. We identified 13 Myrosinase (Myro) and 28 Myrosinase-Binding Protein-like (MBP) genes from Brassica oleracea L. using a comparative genomics approach and characterised them through in silico analyses. We compared the expression patterns of these genes in a clubroot-susceptible line and a resistant line following inoculation with P. brassicae. Two BolMyro and 12 BolMBP genes were highly expressed in the susceptible line, whereas only one BolMyro and five BolMBP genes were highly expressed in the resistant line. Principal component analysis confirmed that specific GSL profiles and gene expression were modulated due to pathogen infection. Plants with higher levels of neoglucobrassicin, glucobrassicin and methooxyglucobrassicin produced disease symptoms and formed galls, whereas, plants with higher levels of sinigrin, hydroxyglucobrassicin and progoitrin produced less symptoms with almost no galls. Our results provide insights into the roles of Myro and MBP genes in GSL hydrolysis during P. brassicae infection, which will help for developing clubroot resistant cabbage lines.

Gamma-rays in the development of rice lines tolerant to aryloxyphenoxypropionate herbicides.

The aryloxyphenoxypropionate (APP) herbicides are graminicides with excellent control of many grass weed species, including weedy rice (Oryza sativa L.). These herbicides block fatty acid biosynthesis by inhibition of the enzyme acetyl-CoA carboxylase (ACCase) and cause death of the plant. Through induced mutation of rice seeds with gamma-rays, rice lines resistant to APP have been developed. Plant dose-response assays confirmed resistance to the APP herbicides quizalofop-p-ethyl and haloxyfop-p-methyl. The carboxyl-transferase (CT) domain fragments of ACCase from the resistant line and the susceptible control were sequenced and compared. A point mutation was detected in the amino acid position 2027. Results indicated that resistance to APP herbicides is a consequence of an altered ACCase enzyme that confers resistance. APP-resistant rice provides an option to improve the efficiency of weed management in rice crops.