Paper on Arabidopsis cold responses - Essay Example

It is widely speculated that the products of these genes have roles in freezing tolerance. The aim of this experiment was to provide direct evidence that supports this hypothesis. It shows that expression of COR15a, which is a cold-regulated gene of Arabidopsis thaliana that encodes a chloroplast-targeted polypeptide, enhances the freezing tolerance of chloroplasts in nonacclimated plants. The Effects of Cold Stress on the Cor15a Promoter of Arabidopsis thaliana In 1985, Guy et al. established that transformations in gene expression occurred in plants during cold acclimation, which is a developmental mechanism that leads to increase in freezing tolerance.

Since then, it has continuously been speculated that some COR (cold-regulated) genes might play roles in freezing tolerance. To investigate this notion, scientists have isolated and characterized genes expressed as a response to low temperature. This has led to the identification of a number of genes such as the cor15a, KIN1, and LTI78 genes of Arabidopsis thaliana; and the pt59 and pao86 genes of barley (“Genome research”, 1995). Arabidopsis thaliana is widely used in botany as the model organism for studying plant genetics and growth responses.

This plant is a member of the mustard (Brassicaceae) family, which includes cultivated species such as cabbage and radish. Although Arabidopsis thaliana does not have any major agronomic importance, it has advantages that make it ideal for use in research in the fields of genetics and molecular biology. The first advantage of Arabidopsis thaliana that make it favorable for research is its small physical size, its fast growth rate, its capability in seed production, its genetic amenability to mutagenesis and transgenic approaches, and the widely available information on its genome.

Secondly, Arabidopsis thaliana is well-suited for analysis with light microscopy. Its seedlings and their roots are translucent and smaller, thus they facilitate live cell imaging with fluorescence and confocal laser scanning microscopy. Lastly, Arabidopsis thaliana is the first plant genome to ever be sequenced. This was completed in 2000 by the Arabidopsis Genome Initiative (Stewart, 2008). Most plants react to low temperatures by altering their intracellular concentrations of free amino acids and carbohydrates, isozyme patterns, and the composition of their membranes.

Moreover, in response to low temperatures, there is an alteration in the activity of many genes. Dr. Michael Thomashow of Michigan State University conducted studies on how plants respond to cold temperatures. He examined cold-induced genes in the plant Arabidopsis and cloned cor (cold related) genes. One of these genes, cor15a, is induced by cold temperatures, drought, and the hormone abscisic acid. Cor15a is a nuclear gene that encodes a 15 kDa protein. The function of this protein is unknown.

This 15 kDa protein is translated to chloroplasts and it may have a function in plant protection from cold. (Baker et al., 1994) isolated a DNA fragment that contained a promoter region and a few amino acids from the cor15a gene. They then joined it to the gusA gene, thereby producing a cor15a-gusAtranslational fusion which was introduced into Arabidopsis thaliana using Agrobacterium. This reporter gene is used in monitoring the response of the cor15agene in varied plant tissues. In this laboratory investigation, transgenic