Project description:Drought represents a major constraint on maize production worldwide. Understanding the genetic basis for natural variation in drought tolerance of maize may facilitate efforts to improve this trait in cultivated germplasm. Here, using a genome-wide association study, we show that a miniature inverted-repeat transposable element (MITE) inserted in the promoter of a NAC gene (ZmNAC111) is significantly associated with natural variation in maize drought tolerance. For maize RNA-seq analysis, pooled tissues from three, eight-day-old maize seedlings were collected from transgenic and wild-type plants, prior to or after 2-hour dehydration, to conduct the RNA-seq analysis.
Project description:Plants have developed complex mechanisms to respond and adapt to abiotic stresses, coupling elaborate modulation of gene expression together with the preservation of genome stability. Epigenetic mechanisms - DNA methylation, chromatin modifications and non coding RNAs - were shown to play a fundamental role in stress-induced gene regulation and may also result in genome destabilization, with the activation and/or the transcription of silenced transposons and retroelements, causing genome rearrangements and novel gene expression patterns. Maize leaf transcriptome was analyzed by total RNA-Seq in both B73 and rmr6 (PolIV mutant involved in siRNA biogenesis and in the RdDM pathway) after drought and salt stress application. Reference annotation based transcript assembly allowed the identification both of new expressed loci and splicing variants, improving the current maize transcriptome annotation. Many antisense transcripts matching on the opposite strand of annotated loci were also identified, while more than the 20% of transcripts represent non coding RNA belonging to four classes: siRNAs, shRNAs, lncRNAs and transposable elements (or their relics). Several lncRNAs are modulated by stress application while TE-related sequences are mainly expressed in rmr6 and up-regulated by the stress.
Project description:PREMISE OF THE STUDY:Positional cloning in combination with phenotyping is a general approach to identify disease-resistance gene candidates in plants; however, it requires several time-consuming steps including population or fine mapping. Therefore, in the present study, we suggest a new combined strategy to improve the identification of disease-resistance gene candidates. METHODS AND RESULTS:Downy mildew (DM)-resistant maize was selected from five cultivars using a spreader row technique. Positional cloning and bioinformatics tools were used to identify the DM-resistance quantitative trait locus marker (bnlg1702) and 47 protein-coding gene annotations. Eventually, five DM-resistance gene candidates, including bZIP34, Bak1, and Ppr, were identified by quantitative reverse-transcription PCR (RT-PCR) without fine mapping of the bnlg1702 locus. CONCLUSIONS:The combined protocol with the spreader row technique, quantitative trait locus positional cloning, and quantitative RT-PCR was effective for identifying DM-resistance candidate genes. This cloning approach may be applied to other whole-genome-sequenced crops or resistance to other diseases.
Project description:Maize is one of the most important crops in the world. With the exponentially increasing population and the need for ever increased food and feed production, an increased yield of maize grain (as well as rice, wheat and other grains) will be critical. Maize grain development is understood from the perspective of morphology, hormone responses, and storage reserve accumulation. This includes various studies on gene expression during embryo development and maturation but a global study of gene expression of the embryo has not been possible until recently. Transcriptome analysis is a powerful new tool that can be used to understand the genetic basis of embryo maturation. We undertook a transcriptomic analysis of normal maturing embryos at 15, 21 and 27 days after pollination (DAP), of one elite maize germplasm line that was utilized in crosses to transgenic plants. More than 19,000 genes were analyzed by this method and the challenge was to select subsets of genes that are vitally important to embryo development and maturation for the initial analysis. We describe the changes in expression for genes relating to primary metabolic pathways, DNA synthesis, late embryogenesis proteins and embryo storage proteins, shown through transcriptome analysis and confirmed levels of transcription for some genes in the transcriptome using qRT-PCR.
Project description:These RNA-seq samples represent ten different tissue types for the fifth version of the maize reference genome B73, sequenced by the NAM Consortium Group. These samples correspond to project ID PRJEB32225.
Project description:RNA-directed DNA methylation (RdDM) in plants is a well-characterized example of RNA interference-related transcriptional gene silencing. To determine the relationships between RdDM and heterochromatin in the repeat-rich maize (Zea mays) genome, we performed whole-genome analyses of several heterochromatic features: dimethylation of lysine 9 and lysine 27 (H3K9me2 and H3K27me2), chromatin accessibility, DNA methylation, and small RNAs; we also analyzed two mutants that affect these processes, mediator of paramutation1 and zea methyltransferase2.
Project description:We perform a quantitative RNA-seq analysis of embryo sacs, comparator ovules with the embryo sacs removed, mature pollen, and seedlings to assist the identification of gametophyte functions in maize. Expression levels were determined for annotated genes in both gametophytes, and novel transcripts were identified from de novo assembly of RNA-seq reads. RNA-seq was performed on four tissue types: nine-day old, above-ground seedling (S); mature pollen (MP); embryo-sac-enriched samples with some remaining nucellar cells (ES); and ovules with embryo sacs removed (Ov).