ABSTRACT
In plants, peptide transporter/nitrate transporter 1 (PTR/NRT1) family proteins transport a variety of substrates such as nitrate, di- and tripepetides, auxin and carboxylates across membranes. We isolated and characterized ZmPTR1, a maize member of this family. ZmPTR1 protein sequence is highly homologous to the previously characterized di- and tripeptide Arabidopsis transporters AtPTR2, AtPTR4 and AtPTR6. ZmPTR1 gene is expressed in the cells of the scutellar epithelium during germination and, to a less extent, in the radicle and the hypocotyl. Arabidopsis thaliana lines overexpressing ZmPTR1 performed better than control plants when grown on a medium with Ala-Ala dipeptide as the unique N source. Our results suggest that ZmPTR1 plays a role in the transport into the embryo of the small peptides produced during enzymatic hydrolysis of the storage proteins in the endosperm.
Subject(s)
Gene Expression Regulation, Plant , Membrane Transport Proteins/genetics , Plant Proteins/genetics , Seeds/genetics , Zea mays/genetics , Amino Acid Sequence , Arabidopsis/genetics , Arabidopsis/growth & development , Arabidopsis/metabolism , Dipeptides/metabolism , Germination , Membrane Transport Proteins/chemistry , Membrane Transport Proteins/metabolism , Molecular Sequence Data , Phylogeny , Plant Proteins/chemistry , Plant Proteins/metabolism , Plant Roots/genetics , Plant Roots/growth & development , Plant Roots/metabolism , Plant Shoots/genetics , Plant Shoots/growth & development , Plant Shoots/metabolism , Plants, Genetically Modified/genetics , Plants, Genetically Modified/growth & development , Plants, Genetically Modified/metabolism , Polymerase Chain Reaction , Seedlings/genetics , Seedlings/growth & development , Seedlings/metabolism , Seeds/growth & development , Seeds/metabolism , Sequence Alignment , Sequence Analysis, DNA , Zea mays/chemistry , Zea mays/growth & development , Zea mays/metabolismABSTRACT
The scutellum is a shield-shaped structure surrounding the embryo axis in grass species. The scutellar epithelium (Sep) is a monolayer of cells in contact with the endosperm. The Sep plays an important role during seed germination in the secretion of gibberellins and hydrolytic enzymes and in the transport of the hydrolized products to the growing embryo. We identified 30 genes predominantly expressed after imbibition in the Sep as compared to other parts of the scutellum. A high proportion of these genes is involved in metabolic processes. Some other identified genes are involved in the synthesis or modification of cell walls, which may be reflected in the changes of cell shape and cell wall composition that can be observed during imbibition. One of the genes encodes a proteinase that belongs to a proteinase family typical of carnivorous plants. Almost nothing is known about their role in other plants or organs, but the scutellar presence may point to a "digestive" function during germination. Genes involved in the production of energy and the transport of peptides were also identified.
Subject(s)
Epithelium/metabolism , Gene Expression Profiling , Gene Expression Regulation, Plant , Germination/genetics , Seeds/anatomy & histology , Seeds/genetics , Zea mays/genetics , Epithelium/embryology , Gene Expression Regulation, Developmental , Gene Library , Genes, Plant/genetics , Organ Specificity/genetics , Reverse Transcriptase Polymerase Chain Reaction , Up-Regulation/genetics , Zea mays/embryologyABSTRACT
BACKGROUND: Camptothecin is a plant alkaloid that specifically binds topoisomerase I, inhibiting its activity and inducing double stranded breaks in DNA, activating the cell responses to DNA damage and, in response to severe treatments, triggering cell death. RESULTS: Comparative transcriptomic and proteomic analyses of maize embryos that had been exposed to camptothecin were conducted. Under the conditions used in this study, camptothecin did not induce extensive degradation in the genomic DNA but induced the transcription of genes involved in DNA repair and repressed genes involved in cell division. Camptothecin also affected the accumulation of several proteins involved in the stress response and induced the activity of certain calcium-dependent nucleases. We also detected changes in the expression and accumulation of different genes and proteins involved in post-translational regulatory processes. CONCLUSIONS: This study identified several genes and proteins that participate in DNA damage responses in plants. Some of them may be involved in general responses to stress, but others are candidate genes for specific involvement in DNA repair. Our results open a number of new avenues for researching and improving plant resistance to DNA injury.
Subject(s)
Camptothecin/pharmacology , Zea mays/drug effects , Zea mays/physiology , Cell Death/drug effects , DNA Damage , DNA Repair , Gene Expression Profiling/methods , Gene Expression Regulation, Plant/drug effects , Genes, Plant/drug effects , Proteomics/methods , Seeds/drug effects , Topoisomerase I Inhibitors/pharmacology , Zea mays/genetics , Zea mays/metabolismABSTRACT
A real-time polymerase chain reaction (QPCR) assay was developed for quantitative detection of a genetically modified (GM) maize event TC-1507 and modification to conventional PCR for qualitative purposes. Sequences 5'-flanking TC-1507 full-length insert were characterized and showed multiple rearrangements involving insert and maize chloroplast fragments. The event specificity of the TC-1507 assays was based on the detection of transgene and plant rearranged sequences found to 5' flank the insertion site. They were fully specific and exhibited a limit of detection below 10 target copies, allowing consistent detection of 0.1% GM levels. The QPCR was highly linear and efficient and proved adequate for quantification of GM contents, aiming at the fulfillment of legal requirements established in the European Union (i.e., compulsory labeling of TC-1507 levels >0.9%). It satisfactorily determined TC-1507 contents on different matrixes and was successfully transferred a different laboratory.
