The Role of Plant Hormones in Organogenesis and the Development of Wild Type and Transgenic Plants
Burnaby South Secondary
Floor Location : S 053 V
Plant tissue culture is a technique with which plant tissue is grown on an artificial nutrient medium under aseptic conditions. Plant hormones are chemical regulators produced by plants, and regulate growth, differentiation and development in plants. The purpose of my experiment was to examine the process of organogenesis in the tissue culture of tobacco (Nicotiana tabacum L) through the use of plant hormones. The second purpose of my project was to transfer a proteinase inhibitor gene (PIN) promoter fused to the -glucuronidase (GUS) reporter gene into tobacco plants through the use of Agrobacterium tumefaciens, and to examine the expression of the introduced transgene. In my first experiment involving the effects of plant hormones on organogenesis, there were four treatment groups: Control, NAA (naphthaleneacetic acid- an auxin) BAP, (benzylaminopurine- a cytokinin) and a group receiving NAA and BAP (high NAA: BAP ratio). In my second experiment involving the generation of transgenic tobacco plants through Agrobacterium tumefaciens, there were two treatment groups: Control and leaf disks treated with Agrobacterium tumefaciens. The cultures were checked once a week for four weeks, where the growth of callus, roots and/or shoots was observed on the cultured leaf pieces. The results of my experiment showed that a combination of NAA and BAP, where the NAA concentration was ten times higher than that of BAP, caused the highest percentage of leaf disks with callus after weeks one through four, and produced a much greater amount of callus per leaf compared to the control group after 5 weeks. Secondly, the treatment of NAA and BAP, where the concentration of BAP was five times greater than that of NAA, resulted in a high percentage of leaf disks (whether control or transgenic) having callus present after weeks one through four. Thirdly, shoot formation only occurred on leaf disks that had been treated with either BAP or with a combination of NAA and BAP, where the BAP concentration was five times greater than that of NAA. Fourthly, root formation only occurred on leaf disks that had received NAA. Transgenic leaf disks (the group infected by Agrobacterium tumefaciens) showed a much lower level of shoot formation as measured by average number of shoots per leaf disk and percent leaf disks with shoots when compared to leaf disks in the control group after weeks three through five. Finally, leaves from the transgenic plants showed a wound-inducible PIN expression response, as assessed by the GUS activity. At present, I am testing the effect of a new plant hormone, epi-brassinolide on organogenesis of tobacco leaf tissues. For my future studies, I am planning to compare the transgenic and wild type tobacco plants, with or without the application of plant hormones, jasmonic acid and cytokinin for their insect resistance activities.