Gene Expression In Maize Research Articles

The effects of cold-temperature stress on gene expression in maize

A rapid decrease from the 28 °C incubation temperature of 5-day-old maize seedlings induced a response recorded as an altered synthesis of several polypeptides. The maximum response occurred at 4 °C and included cold-shock proteins with relative molecular masses of 94, 92, 90, 73, 70, 54, 50, 44, 38, 34, 33, 32, 24, 20, and 14 kilodaltons (kDa). Western bolt analysis (probed with polyclonal antibodies against maize heat-shock proteins) and fluorograms prepared from one-dimensional gel electrophoresis of maize heat-shock proteins revealed differences between the cold-induced polypeptides and the maize heat-shock proteins. The abundance of low molecular weight polypeptides and the absence of a marked depression in normal protein synthesis were the most noted differences from the heat-shock response. The cold-shock response, which was induced by as little as a 3 °C reduction in temperature, showed some transitory proteins, was separate from an acclimation response, and lasted up to 18 h (after returning the seedlings to 28 °C) before the normal protein synthetic pattern returned. Seedlings allowed to recover from a 4 °C shock for 4 h at 28 °C showed synthesis of a 250-kDa polypeptide, which lasted less than 2 h and was completely inhibited by actinomycin D.

Cell-Specific Photosynthetic Gene Expression in Maize Determined Using Cell Separation Techniques and Hybridization in Situ

Bundle sheath strands and mesophyll cell extracts have been isolated from maize (Zea mays L.) leaves using a mechanical disruption-filtration technique. Northern blot analysis showed that phosphoenolpyruvate carboxylase (PEPCase; EC 4.1.1.31) mRNA accumulates only in mesophyll cells. The mechanisms regulating the cell-specific expression of this gene must, therefore, be at either the level of RNA transcription or that of mRNA turnover. The first successful application of hybridization to mRNA molecules in photosynthetic plant tissue sections is described. Results obtained from this in situ study corroborate our finding that PEPCase mRNA accumulates only in mesophyll cells as well as the previously reported (Link, G, DM Coen, L Bogorad 1978 Cell 15: 725-731) finding that the accumulation of ribulose 1,5-bisphosphate carboxylase (RuBPCase; EC 4.1.1.39) large subunit mRNA is restricted to bundle sheath cells. Demonstrating the differential accumulation of PEPCase mRNA and RuBPCase mRNA by utilizing the in situ hybridization technique paves the way for its use as a powerful tool in relating cellular differentiation to gene expression during plant development.

The structure and expression of maize genes encoding the major heat shock protein, hsp70

We have isolated and sequenced two maize genomic clones that are homologous to the Drosophila hsp70 gene. One of the maize hsp70 clones contains the entire hsp70 coding region and 81 nucleotides of the 5' nontranslated sequence. The predicted amino acid sequence for this maize protein is 68% homologous to the hsp70 of Drosophila. The second maize hsp70 clone contains only part of the coding sequence and 1.1 kb of the 5' flanking sequence. This 5' flanking sequence contains two sequences homologous to the consensus heat-shock-element sequence. Both maize genes are thermally inducible and each contains an intron in the same position as that of the heat-shock-cognate gene, hsc1, of Drosophila. The presence of an intron in the maize genes is a distinguishing feature in that no other thermally inducible hsp70 genes described to date contain an intron. We have constructed a hybrid hsp70 gene containing the entire hsp70 coding sequence with an intron, and 1.1 kb of the 5' flanking sequence. We demonstrate that this hybrid gene is thermally inducible in a transgenic petunia plant and that the gene is expressed from its own promoter.

Haplodiploid gene expression in maize and its detection.

A method for the demonstration of the gametophytic origin of genetic variability in maize is described. For genes coding dimeric or multimeric enzymes, haploid expression can be demonstrated by means of translocations between A and B chromosomes (TB-A), which make it possible to obtain hyperploid pollen grains, partially diploid and heterozygous for electrophoretic mobility. Comparison of the electrophoretic pattern of this pollen type (three bands) and that of normal grains produced by a heterozygous F/S plant (two bands only) reveals haploid transcription of the monomeric forms. The procedure was tested on ADH-1 and used to demonstrate haploid expression for GOT-1. The data obtained suggest, moreover, that the reduction in male gamete transmission of duplications may be due to differences in pollen competitive ability rather than to processes affecting microspore maturation.

Regulation of expression of Adh genes in maize.

A regulatory mutant of the Adh (alcohol dehydrogenase) gene was induced by ethyl methanesulfonate. The mutation reduces the ability of the gene to complete for the limited gene activating factor. The mutant shows full activity in the homozygote but only one-half the activity of the progenitor gene in heterozygotes where it is competing with another allele for the limited factor. Evidence is presented for multiple regulatory sites in both the Adh and Adh2 loci.