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Functional Analysis of Genes Expressed in Response to Light and Gravity Stimulation in Arabidopsis Root Tips.  J. Huang, R. Hammond, S. Hume, J. Dalal, C. Brown, H. Winter-Sederoff, North Carolina State University, Raleigh, NC.

   Light and gravity give clues about time and space which plants use to direct their growth. Roots grow towards the vector of gravity (positive gravitropism), towards blue light (positive phototropism) and away from red light (negative phototropism). Specific genes have been identified in roots from Arabidopsis thaliana seedlings that are expressed when the dark-grown seedlings are gravity stimulated by reorientation. Several of those genes also respond to directional light (Salinas-Mondragon et al. 2005).

   To test whether these genes (protein products) are essential for gravitropism or phototropism, we analyzed the Arabidopsis knockout lines for these genes for their overall phenotypic changes as well as response to directional blue light and reorientation in the light or dark. Knockout lines were ordered from SALK or CSHL and selved. Several of those heterozygeous knockout lines did not produce homozygeous seed. From those lines that did produce viable homozygeous seeds (At2g16005 = ET11532; At5g38020 = SamT like, CS827371) we generated F3 lines, and analyzed the kinetics of bending toward directional blue and white light as well as reorientation by 90° in the light and in the dark. For these measurements we used a newly developed Plant Movement Imaging device which images and calculates the rate and direction of plant growth.

Salinas-Mondragon, R., Brogan, A., Ward, N., Perera, I., Boss, W., Brown, C.S. and Sederoff, H.W. (2005) Gravity and light: integrating transcriptional regulation in roots. Gravity Space Biol Bull, 18, 121-122.

Acknowledgement: This work was supported by NC Space Grant Undergraduate Student Summer Research Grant to J. H.