MOLECULAR GENETIC APPROACHES TO PEST AND PATHOGEN RESISTANCE IN SUGAR BEET, BETA VULGARIS L.
Title: Stress Induced Expression of a Beta vulgaris L. Gene for a Chloroplast-Targeted Signal Calmodulin-Binding Protein
Submitted to: Advanced Studies in Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 30, 2008
Publication Date: November 2, 2009
Citation: Kuykendall, L.D., Shao, J.Y., Kurushko, T., Burdekin, K.A. 2009. Stress Induced Expression of a Beta vulgaris L. Gene for a Chloroplast-Targeted Signal Calmodulin-Binding Protein. Advanced Studies in Biology. 1(7):323-332.
Interpretive Summary: Diseases caused by pathogenic microorganisms currently reduce both profitability and sustainability of sugar beet production. Climate change or global warming lowers resistance in temperate crops, and controlling plant diseases is vital. In this study some of the sugarbeet “chromosomal DNA,” or the plant’s hereditary material, was studied at the molecular level. A cluster of several genes which play roles in heat tolerance and disease resistance was discovered. Of these genes, one called “CaMP,” was the subject of recent research focus and, experimentally in the greenhouse and in the lab, the gene’s level of expression was found to be enhanced either by bacterial infection or elevated temperature. This gene is part of a system plants have evolved to protect them from stress. Therefore, manipulation of the stress-responsive CaMP gene is planned in order to improve disease and temperature stress resistance and the results will likely be useful to many scientists who investigate plant genomics and breeders who improve disease resistance in order to enhance crop production. Moreover, the finding of similar gene clusters in other plant species such as tomato, grape, poplar and a so-called “model” legume is fully expected to be of considerable interest to the entire plant science community.
In sugarbeet, Beta vulgaris L., Medicago truncatula Gaertn and Populus trichocarpa Torr & Gray, a cluster of orthologous genes includes NPR1, a disease resistance-controlling gene, CaMP, encoding a calmodulin-binding protein and CK1PK, determining a dual-specificity casein kinase 1-class protein kinase. HSF is downstream of NPR1 in sugarbeet and popular but not in Medicago. CaMP, located between CK1PK and NPR1 in sugarbeet, is shown to exhibit enhanced transcriptional expression under stress conditions – either elevated substrate temperature or following experimental infection by Erwinia betavasculorum. The predicted protein product of CaMP in sugarbeet has an N-terminal 17-amino acid signal peptide, predicted by SignalP and SMART, identified as chloroplast-targeted by both TargetP and ChloroP. Interestingly, the Beta vulgaris CaMP gene product exhibits significant amino acid sequence homology, over a large internal conserved domain, with an as yet largely undefined family of IQ domain calmodulin-binding proteins in plants. The biological function of sugarbeet’s homologous CaMP gene’s protein product is unknown. However, bioinformatic analysis has shown that the protein is an IQ-domain calmodulin-binding protein with a chloroplast-targeted N-terminal peptide. Homologous genes in Solanum lycopersicum, Vitis vinefera, Populas trichocarpa, Arabdopsis thaliana and Medicago truncatula produce a protein product featuring (1) highly significant amino acid alignment with the Beta vulgaris CaMP product and (2) a chloroplast-targeted signal peptide (with an additional possible transit of the Medicago protein into the mitochondria). Further, conserved microsynteny of CaMP, CK1PK, NPR1, and HSF genes was found in Vitis vinifera; while in Solanum lycopersicum, similarly to the earlier findings in Medicago truncatula, conservation of microsynteny of CaMP with CK1PK and NPR1 genes was found, but not HSF.