Lipid Metabolism in Corn Tissue Culture and Molecular Biology of Soybean Seed Maturation

127 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.Lipid metabolism of corn (Zea mays) tissue culture was studied using seven strains or inbred lines. The lipid content from the embryogenic callus derived from these lines followed the same trend as the lipid content found in the seeds, however there was no consistent lipid pattern observed for the leaf or root callus from these same lines relative to the tissue that it originated from. Therefore corn embryogenic callus provides an ideal tissue to study lipid metabolism. Embryogenic calli were also used to select cell lines resistant to cerulenin, an inhibitor of fatty acid synthesis. While it was hypothesized that the cerulenin-resistant calli might be an overproducing-oil line, the selected resistant calli did not exhibit an increase in lipid content relative to the control calli.A variant corn callus induced from etiolated corn leaves from Illinois High Oil strain was identified. The variant callus has increased lipid content concomitant with increased acetyl-CoA carboxylase activity and altered biotin-containing protein patterns relative to the wild type callus. The variant callus also exhibited an altered fatty acid composition concomitant with decreased oleic acid desaturase activity. Thus it appears that acetyl-CoA carboxylase and oleic acid desaturase are important regulatory enzymes in lipid metabolism.Gene expression during precocious and natural maturation of soybean (Glycine max) seeds was investigated by cloning the cDNAs corresponding to the mRNAs which were expressed only during maturation. The cDNA clones were isolated by construction of a cDNA library from poly(A)\sp+RNA from four days pod dried 35 days after flowering (DAF) soybean seeds followed by differential hybridization. The soybean seed maturation polypeptide gene appears to be switched on in precociously dried immature (35 DAF) seeds or naturally maturing seeds. The maturation cDNA clones were shown to encode a 31 kD protein and this protein is encoded by a single copy or relatively low copy genes.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Genome-wide analysis of polycistronic microRNAs in cultivated and wild rice

MicroRNAs (miRNAs) are small noncoding RNAs that direct posttranscriptional gene silencing in eukaryotes. They are frequently clustered in the genomes of animals and can be independently transcribed or simultaneously transcribed into single polycistronic transcripts. Only a few miRNA clusters have been described in plants, and most of them are generated from independent transcriptional units. Here, we used a combination of bioinformatic tools and experimental analyses to discover new polycistronic miRNAs in rice. A genome-wide analysis of clustering patterns of MIRNA loci in the rice genome was carried out using a criterion of 3 kb as the maximal distance between two miRNAs. This analysis revealed 28 loci with the ability to form the typical hairpin structure of miRNA precursors in which 2 or more mature miRNAs mapped along the same structure. RT-PCR provided evidence for the polycistronic nature of seven miRNA precursors containing homologous or nonhomologous miRNA species. Polycistronic miRNAs and candidate polycistronic miRNAs are located across different rice chromosomes, except chromosome 12, and resided in both duplicated and nonduplicated chromosomal regions. Finally, most polycistronic and candidate polycistronic miRNAs showed a pattern of conservation in the genome of rice species with an AA genome. The diversity in the organization of MIR genes that are transcribed as polycistrons suggests a versatile mechanism for the control of gene expression in different biological processes and supports additional levels of complexity in miRNA functioning in plants

Genome-wide analysis of polycistronic microRNAs in cultivated and wild rice

MicroRNAs (miRNAs) are small noncoding RNAs that direct posttranscriptional gene silencing in eukaryotes. They are frequently clustered in the genomes of animals and can be independently transcribed or simultaneously transcribed into single polycistronic transcripts. Only a few miRNA clusters have been described in plants, and most of them are generated from independent transcriptional units. Here, we used a combination of bioinformatic tools and experimental analyses to discover new polycistronic miRNAs in rice. A genome-wide analysis of clustering patterns of MIRNA loci in the rice genome was carried out using a criterion of 3 kb as the maximal distance between two miRNAs. This analysis revealed 28 loci with the ability to form the typical hairpin structure of miRNA precursors in which 2 or more mature miRNAs mapped along the same structure. RT-PCR provided evidence for the polycistronic nature of seven miRNA precursors containing homologous or nonhomologous miRNA species. Polycistronic miRNAs and candidate polycistronic miRNAs are located across different rice chromosomes, except chromosome 12, and resided in both duplicated and nonduplicated chromosomal regions. Finally, most polycistronic and candidate polycistronic miRNAs showed a pattern of conservation in the genome of rice species with an AA genome. The diversity in the organization of MIR genes that are transcribed as polycistrons suggests a versatile mechanism for the control of gene expression in different biological processes and supports additional levels of complexity in miRNA functioning in plants

Transcriptome Profiling of Leaf Elongation Zone under Drought in Contrasting Rice Cultivars

<div><p>Inhibition of leaf elongation and expansion is one of the earliest responses of rice to water deficit. Despite this sensitivity, a great deal of genetic variation exists in the extant of leaf elongation rate (LER) reduction in response to declining soil moisture. We analyzed global gene expression in the leaf elongation zone under drought in two rice cultivars with disparate LER sensitivities to water stress. We found little overlap in gene regulation between the two varieties under moderate drought; however, the transcriptional response to severe drought was more conserved. In response to moderate drought, we found several genes related to secondary cell wall deposition that were down regulated in Moroberekan, an LER tolerant variety, but up-regulated in LER sensitive variety IR64.</p> </div

Cell Wall DEGs.

<p>Fold change difference for all cell wall annotated genes with at least two-fold change under mild stress in both IR64 (solid bars) and Moroberekan (striped bars).</p

Expression level polymorphisms for each condition at FDR 0.1 and 0.01.

<p>Expression level polymorphisms for each condition at FDR 0.1 and 0.01.</p

Relative leaf elongation under soil drying.

<p>Bars represent +/- SE.</p