Anthranilate synthase (AS) is a key regulatory enzyme in tryptophan (Trp) biosynthesis and feedback inhibition by Trp. it is used as a biomarker of pathophysiological and physiological conditions mediated By ASA2 gene. In this study, we investigated the effect of tryptophan modifications by ASA2 gene and the possible importance of its modification in enhancing defense mechanism. The gene encoding ASA2α&β under the control of 35S promoter was introduced into maize callus Type II by particle bombardment with 1100 psi single and double shot. A total of eleven different transgenic lines showed markedly increased accumulation of free Trp. In spite of the marked increase in free Trp content, metabolic profiling was done by high – performance liquid chromatography coupled with amino acid analyzer. The results of this study pointed to develop a reproducible and efficient method for inserting genes into nuclear genome of many important plant species using the naturally occurring feedback-insensitive anthranilate synthase gene ASA2 from tobacco. The double shot protocol recorded low number of amino acids of produced plantlets and significant increases in Trp concentration comparing to single shot and control. These results indicate that transformation with ASA2α& β gene is a reliable approach to improve the defense mechanism of maize and increase the nutritional quality of maize which is very important for human and animal food.
Key words: Maize, Defense Mechanism, tryptophan, anthranilate synthase gene
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