Calcium/calmodulin-mediated gravitropic response in plants.
Calcium and calmodulin (CaM) play an important role in gravity signal transduction. However, the molecular and biochemical mechanisms involved in gravity signal transduction are not clearly understood. It is becoming evident that hydrogen peroxide is involved in gravity-induced response. Recent results indicate that Ca 2+/CaM is involved in hydrogen peroxide homeostasis by regulating catalase activity in plants (Yang and Poovaiah, 2002). It is well established that auxin controls differential growth during gravitropic bending. Results indicated that an auxin-responsive gene family (SAURs) encodes for Ca 2+ /CaM-binding proteins (Yang and Poovaiah, 2000a). To investigate the effects of gravity on the expression of genes involved in Ca 2+/CaM-mediated signaling, Arabidopsis and corn seedlings were subjected to simulated microgravity using the Random Positioning Machine (RPM), and hypergravity using the MidiCAR centrifuge. The changes in mRNA levels were studied. Selective and significant differences in gene expression were observed in simulated microgravity- and hypergravity- treated plants. The relevance of these genes in gravity signal perception and transduction is discussed.
Poovaiah
B W
BW
Laboratory of Plant Molecular Biology and Physiology, Department of Horticulture, Washington State University, Pullman, WA, USA.
Yang
T
T
van Loon
J J W A
JJ