Yun, H.S., Department of Life Science, Chung-Ang University, Seoul 156-756, South Korea
Joo, S.-H., Department of Life Science, Chung-Ang University, Seoul 156-756, South Korea
Kaufman, P.B., Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 830 North University Street, Ann Arbor, MI 48109-1048, United States
Kim, T.-W., Department of Life Science, Chung-Ang University, Seoul 156-756, South Korea
Kirakosyan, A., Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 830 North University Street, Ann Arbor, MI 48109-1048, United States
Philosoph-Hadas, S., Department of Postharvest Science of Fresh Produce, Volcani Center, ARO, POB 6, Bet Dagan, 50250, Israel
Kim, S.-K., Department of Life Science, Chung-Ang University, Seoul 156-756, South Korea
Chang, S.C., University College, Yonsei University, Seoul 120-749, South Korea
Joo, S.-H., Department of Life Science, Chung-Ang University, Seoul 156-756, South Korea
Kaufman, P.B., Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 830 North University Street, Ann Arbor, MI 48109-1048, United States
Kim, T.-W., Department of Life Science, Chung-Ang University, Seoul 156-756, South Korea
Kirakosyan, A., Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 830 North University Street, Ann Arbor, MI 48109-1048, United States
Philosoph-Hadas, S., Department of Postharvest Science of Fresh Produce, Volcani Center, ARO, POB 6, Bet Dagan, 50250, Israel
Kim, S.-K., Department of Life Science, Chung-Ang University, Seoul 156-756, South Korea
Chang, S.C., University College, Yonsei University, Seoul 120-749, South Korea
This study was conducted to unravel a mechanism for the gravitropic curvature response in oat (Avena sativa) shoot pulvini. For this purpose, we examined the downward movement of starch-filled chloroplast gravisensors, differential changes in inositol 1,4,5-trisphosphate (IP 3) levels, transport of indole-3-acetic acid (IAA) and gravitropic curvature. Upon gravistimulation, the ratio for IAA levels in lower halves versus those in upper halves (L/U) increased from 1.0 at 0 h and reached a maximum value of 1.45 at 8 h. When shoots were grown in the dark for 10 d, to deplete starch in the chloroplast, the gravity-induced L/U of IAA was reduced to 1.0. N-naphthylphthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA), both auxin transport inhibitors, significantly reduced the amount of gravitropic curvature and gravity-induced lateral IAA transport, but did not reduce the gravity-induced late change in the L/U ratio of IP 3 levels. U73122, a specific phospholipase C (PLC) inhibitor, decreased gravity-induced curvature. Because U73122 reduced the ratio of L/U of IAA imposed by gravistimulation, it is clear that IAA transport is correlated with changes in IP 3 levels upon gravistimulation. These results indicate that gravistimulation-induced differential lateral IAA transport may result from the onset of graviperception in the chloroplast gravisensors coupled with gravity-induced asymmetric changes in IP 3 levels in oat shoot pulvini. © 2006 The Authors.
