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Transcriptome analysis of germinating maize kernels exposed to smoke-water and the active compound KAR1

ABSTRACT: Smoke released from burning vegetation functions as an important environmental signal promoting the germination of many plant species following a fire . It not only promotes the germination of species from fire-prone habitats, but several species from non-fire-prone areas also respond, including some crops. Bioactivity-guided fractionation of smoke-water led to the identification of a highly active butenolide compound, 3-methyl-2H-furo[2,3-c]pyran-2-one. Several hypotheses have arisen regarding the molecular background of smoke and butenolide action. Contrary to the efforts to unravel the mode of action of smoke, the mechanism is still largely unknown. In this paper we demonstrate that although smoke-water and butenolide treatment of maize kernels results in a similar physiological response, the gene and protein expression patterns are quite different. Treatment with smoke-water enhanced the ubiquitination of proteins and activated protein-degradation-related genes. This effect was completely absent from butenolide-treated kernels, in which a specific aquaporin gene was distinctly upregulated. These findings indicate that other bioactive compounds present in smoke-water may act together, leading to accelerated protein turnover. The results highlight the importance of protein degradation and aquaporins in the seed germination process. Besides their obvious use in the sustainable agricultural practice, smoke and butenolide can be used in studies to gain further insight into the transcriptional changes during germination.

ORGANISM(S): Zea mays

PROVIDER: GSE17484 | GEO | 2009/08/24

SECONDARY ACCESSION(S): PRJNA118755

REPOSITORIES: GEO

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Project description:Smoke released from burning vegetation functions as an important environmental signal promoting the germination of many plant species following a fire . It not only promotes the germination of species from fire-prone habitats, but several species from non-fire-prone areas also respond, including some crops. Bioactivity-guided fractionation of smoke-water led to the identification of a highly active butenolide compound, 3-methyl-2H-furo[2,3-c]pyran-2-one. Several hypotheses have arisen regarding the molecular background of smoke and butenolide action. Contrary to the efforts to unravel the mode of action of smoke, the mechanism is still largely unknown. In this paper we demonstrate that although smoke-water and butenolide treatment of maize kernels results in a similar physiological response, the gene and protein expression patterns are quite different. Treatment with smoke-water enhanced the ubiquitination of proteins and activated protein-degradation-related genes. This effect was completely absent from butenolide-treated kernels, in which a specific aquaporin gene was distinctly upregulated. These findings indicate that other bioactive compounds present in smoke-water may act together, leading to accelerated protein turnover. The results highlight the importance of protein degradation and aquaporins in the seed germination process. Besides their obvious use in the sustainable agricultural practice, smoke and butenolide can be used in studies to gain further insight into the transcriptional changes during germination. 15 individual kernels from each of six biological replicates were chosen and equal amount of the aaRNA samples were pooled. Three technical replicates were applied at each time point for the microarray analysis. For the control versus butenolide experiment the samples were collected at 1.5, 3, 6, 9, 12 and 24 hours after treatment. For the control versus smoke experiment the samples were collected at 1.5, 3, 6, 9, 12, 24 and 27 hours after treatment. For the delayed experiment samples were collected after 3 or 6 hours after treatment.

Project description:Sensing environmental cues is essential for plants in order to respond properly to, adapt to and survive changes in the environment and disturbances. Smoke-derived germination active compounds are important cues which provide a strong chemical signal to seeds in the soil seed bank about the available germination niche created by the passage of fire. The germination stimulatory activity can largely be attributed to the presence of the butenolide, 3-methyl-2H-furo[2,3-c]pyran-2-one (karrikinolide; KAR1). More recently, a related fire-borne butenolide, 3,4,5-trimethylfuran-2(5H)-one (inhibenolide A; InhA), was shown to have an inhibitory effect on germination. The aim of this study was to extensively characterize the interaction of these potent smoke-derived compounds in the highly KAR1-sensitive Lactuca sativa cv. M-bM-^@M-^XGrand RapidsM-bM-^@M-^Y achenes. A time course microarray analysis of KAR1- and InhA-treated achenes was performed using custom-made Agilent microarrays. Early time points for sampling the transcriptome were chosen by taking into account the fact that treatment with KAR1 is irreversible (by leaching with water) after 2 h, and that the KAR1-treated achenes enter an InhA-insensitive stage after 9 h. Therefore, samples were harvested after 2 and 10 h of initial exposure to 0.1 M-BM-5M KAR1 or 10 M-BM-5M InhA, and after 24 h, when germinated and non-germinating achenes could be distinguished visually. To assess the divergence between the expression patterns induced by the two compounds, a sample of achenes treated with 0.1 M-BM-5M KAR1 and 10 M-BM-5M InhA simultaneously, was harvested after 2 h. At 24 h, samples were collected from germinating and non-germinating achenes separately, and equal amounts of mRNA were pooled. Although this design implies that there is a small chance of losing data, our primary aim at 24 h was to screen for differences between the KAR1- and InhA-induced transcriptome. Achenes germinated in distilled water served as controls and were compared to the experimental samples treated as described above.

Project description:Fusarium verticillioides is a detrimental fungus that can contaminate maize grains with mycotoxins that are harmful to human and animal health. Breeding and growing resistant genotypes is one alternative to reduce contamination and subsequent production of mycotoxins by this fungus. However, little is known about the resistant mechanism relevant to breeding in this pathosystem. Therefore, our aim was to identify genes and metabolites that may be related to Fusarium ear rot resistance using resistant and susceptible maize inbreds. Kernels of the resistant inbred showed significantly reduced disease severity, and reduced levels of total fumonisin and ergosterol content compared with the susceptible one. Gene expression data were obtained from microarray hybridizations using F. verticillioides inoculated and non inoculated maize kernels. Differentially expressed sequences were identified and classified into 36 functional categories. Most of the differentially expressed genes were assigned to the categories “protein, RNA, DNA, stress, transport, signaling and cell metabolism”. These genes encode for PR proteins, detoxification and primary metabolism enzymes. Fungal inoculation did not produce considerable changes in gene expression and metabolites in the resistant L4637 inbred, probably due to a preformed or constitutive resistance mechanism. Defense-related genes were induced or repressed in kernels of the susceptible inbred L4674, responding specifically to the pathogen infection. The qRT-PCR in infected silks showed that glucanase, lipid transfer, xylanase inhibitor, PR1 and 26S proteosome transcripts had higher expression ratios in the susceptible line compared to the resistant one in response to fungal infection. Through this study, a global view of differential genes expressed and metabolites concentration during resistance and susceptibility to F. verticillioides inoculation has been obtained, giving additional information about the mechanisms and pathways conferring resistance to this important disease in maize.

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Transcriptome analysis of germinating maize kernels exposed to smoke-water and the active compound KAR1

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