GENETICALLY MODIFIED MAIZE

Literature Review: Genetically Modified Maize



Literature Review: Genetically Modified Maize

Introduction

With application of genetic modification to various plant resources and their spread in commerce, to develop the reliable method with which to detect transgenic DNA and expressed proteins in products is of considerable importance because it enables us to evaluate effects of recombinant DNA. Methods of detecting recombinant DNA in potatoes and soybeans have been described and maize has also been the subject of recombinant DNA detection study. Polymerase chain reaction (PCR) is the popular method to amplify transgenic recombinant DNA segments, it to detect recombinant DNA in genetically modified maize (GM- maize) . Though their methods could detect recombinant DNA, they were not able to determine various lines of GM- maize. There are different lines of approved GM- maize and distinguishing between them is the major issue for quality assessment. Matsuoka and Matsuoka developed the method to detect recombinant DNA from different lines of GM- maize. Adopting PCR to detect recombinant DNA is useful, but its procedures are complex and it requires expensive equipment. Therefore, enzyme-linked immunosorbent assays (ELISAs) have also been used by farmers as the screening tool due to its simplicity, convenience and cost-effectiveness.

The United States of America announced in 2001 that 22% of maize seeds in examined 6000 samples were StarLink™ seeds. in 2001, recombinant DNA in an unauthorized line of potatoes was detected in potato chips and products were recalled. The loss to food company grew to 400 million Dollar (about 3 million US dollars). Whether to label and how to label genetically modified products are controversial issues, so food producers need to know if and how much their raw materials have been genetically modified. Thus, evaluation of detection methods is essential, and obtaining information about content of genetically modified crops in imported products is particularly important to, which relies heavily on food imports. This study describes two detection methods of GM- maize and state of its import.

Plants

GM- maize (Zea mays) seeds imported from USA were provided by Ministry of Health, Labour and Welfare (MHLW) . These seeds had been genetically modified to acquire insect resistance and (or) herbicide tolerance. Cry1A(b) gene (Koziel et al., 1997) from Bacillus thuringiensis (Bt) and (or) phosphinothricin N-acetyltransferase (pat) gene (Wohlleben et al., 1988) from Streptomyces viridochromogenes had been introduced into genome for insect resistance and (or) herbicide tolerance, respectively. Non- genetically modified maize (non-GM- maize) seeds were also provided by MHLW .

DNA extraction

As in earlier report (Yamaguchi et al., 2000), DNA was extracted using the modification of methods.Milled maize seeds (20 mg) were mixed in the 1% cetyltrimethylammonium bromide (CTAB) buffer consisting of 50 mM Tris-HCl (pH 8.0), 700 mM NaCl and 10 mM EDTA and homogenized at 65 °C using the motar and pestle then placed at same temperature for 10 min. Phenol:chloroform:3-methyl-1-butanol (25:24:1, 400 µl) was added to crude extract, which was gently mixed and centrifuged at 16,000×g for 5 min. The mixture was separated into three layers. The upper layer containing nucleic acids was ...