The Stress Effects of Phototropism and Different Colored Lights on Arabidopsis Wild-type and Mutant Strains. By: Brad Cole Rita Hunt-Woodland Monarch High School

Purpose of Project We investigated the effects of phototropism (full spectrum, blue light, red light, and black light) on Arabidopsis wild-type and mutant strains in order to determine the possible functions of the DCL-4 and RDR-6 genes when the plant is put under stress.

Why use Arabidopsis? Short life cycle 6-8 weeks Small convenient to grow plant Easily matched environmental conditions Small genome Has been completely genetically mapped Closely resembles genes in crop plants

RDR6 and DCL4 Mutants Arabidopsis contains the genes for RDR 1-6, and DCL genes 1-4. RDR - RNA dependant polymerase. DCL - Dicer Like

RNAi is the immune response of the plant. The RISC complex cleaves viral looking double stranded RNA within the cytoplasm of the cell so that the enzyme/protein can never be produced.

Hypotheses 1.If our Arabidopsis plants rely on blue-violet light and red light in order to grow (this is according to Engelmann's theory that plants perform photosynthesis faster when blue-violet and red light are present), and we put our wild type and mutant strands into purely blue light to grow for 30 days, then the growth will not occur as fast because the plants rely on both the red and blue –violet light and the plants in this stressed condition will not get the red light in order to aid in photosynthesis and will have only light blue light instead of the preferred blue-violet light.

Hypotheses cont. If our Arabidopsis plants rely on both blue-violet and red light to grow faster, and we place both our wild type and mutant strands in red light to grow for 30 days, then the plants will grow as if it were under normal conditions or more efficient than under normal conditions because the plants need red light in order for optimization of the light dependent reactions in photosynthesis and with the red light being in abundance then the plants will continue to grow normally.

Hypothesis cont. If the black light produces UV rays and a dark violet light which creates high energy frequencies and can mutate DNA, and we place our wild type and mutant strands in the black light to grow for 30 days, then the plants will not be able to grow and if they do grow then the color pigments will be mutated.

Hypotheses cont. If our Arabidopsis requires light and water in order to grow and perform photosynthesis, and we continuously switch the plants from growing in light and growing in dark, then our plants will continuously grow because although the light is only not present for a week at a time the plants still need continuous light in order to perform photosynthesis.

Methods In our experiment we looked at the effects of phototropism, red light, blue, and black light on Arabidopsis wild type and mutant strands. In order to complete this we had to build a box in which we could test the phototropism and all the different colored lights. The box that we constructed had a door and three dividers so that we could separate all of the different light colors from each other. By doing this the dividers acted a s barriers so that each light would not leak into any of the other sections. This allowed us to get different results for each color of light.

Watered Over the course of 4-6 weeks we continued to water the plants every other day with the normal nutrient water that is needed to maintain growth and development in our plants. Our water consisted of Miracle Grow for indoor plants and each tray received 1400 milliliters of water.

Conclusion Plants need a specific wave length and amount of light. Plants need a constant amount of light to convert the light energy to chemical energy in order to grow and maintain life. There is a direct connection between environmental stresses and expression of RNAi and other developmental genes.

Conclusion cont. Under the black light, there was little to no growth and when there was growth the plants were albino. UV wave lengths affect the growth of plants because there isn’t the necessary light in order for the plant to grow and develop. The UV light was not the preferred energy for the photosynthetic pigments. So we were not seeing the normal pigments, and the plants were albino. There seems to be a link with environment (epigenetic effects) and DNA/RNAi expression. The stems were long and narrow, and wilted easily which made us conclude that the plants were reaching up higher than they usually would in order to find the necessary light. Because there was not enough of the necessary light the plants all died within 4 weeks. We are re-testing this to see if we obtain the same results.

Conclusion cont. Like under the Black Light, there was minimal growth under both the red and blue light. We tested the red and the blue light separately because we knew that with photosynthesis, plants prefer red and blue-violet light. So when there is a mixture of the two we knew that there would be growth, but we wanted to see what would happen when we separated the colors of light. Our conclusion is that the plants needed both the red and the blue-violet light in order to perform photosynthesis and to convert the light energy to chemical energy. Growth and development of the plant will be minimal without both the red and the blue light mixed together. We are re-testing this by mixing the blue and red light together in order to see what the growth pattern is.

We’d like to thank… Dr. Lisa Johansen for helping us by supplying us with seeds and soil, and for checking in with us to see how our plants are growing. Mrs. Kristin Donley for helping us with our ideas for how to grow our plants and for her overall guidance.

Bibliography http//: hydroponics-gardening.com; September 2008 Andrew Fire and Craig Mellow, (2006) the Nobel prize in physiology/medicine (http//:nobelprize.org) Elliot Meyerowitz, Prehistory and History of Arabidopsis Research, Plant Physiology, January 2001, vol. 125, pp Sabina Leonelli, Arabidopsis, the Botanical Drosophilia: from Mouse Cress to Model Organism; March 2007, Endeavor, vol. 31 No. 1, pp.34-38

Bibliography Andrew Fire and Craig Mello. “The Nobel Prize In Physiology or Medicine for 2006.” NobelPrize.org. November 20, Fralin Biotechnology Center. “PREP Experiment Guide”. Virginia Polytechnic Institute and State University. Dec. 1,