The role of calcium ions in gravity signal perception and transduction.
Ca2+ is implicated as a messenger in coupling various environmental stimuli, such as gravity and light, to response.  In recent years, it has become evident that Ca2+ plays a central role in all three phases of gravitropism--perception, transduction and response.  The root cap, which is known to contain high amounts of Ca2+ and calmodulin, is the primary site of gravity perception.  The possible role of phosphoinositide turnover and Ca(2+) - and Ca(2+) -calmodulin-dependent enzymes such as Ca(2+) -ATPase and protein kinases in gravitropism is discussed.  A model is proposed to describe the role of Ca2+ in both normal and light-dependent gravity response in roots.
Poovaiah
B W
BW
Dept of Horticulture and Land. Architecture, Washington State University, Pullman 99164-6414, USA.
McFadden
J J
JJ
Reddy
A S
AS
D002118:Calcium / Q000032:analysis / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000502:physiology; D002147:Calmodulin / Q000032:analysis / Q000502:physiology; D018522:Gravitropism / Q000502:physiology*; D018466:Gravity Sensing / Q000502:physiology*; D008027:Light; D063245:Plant Development; D018521:Plant Physiological Phenomena; D018518:Plant Root Cap / Q000737:chemistry / Q000254:growth & development / Q000502:physiology; D010944:Plants / Q000737:chemistry; D015398:Signal Transduction / Q000502:physiology*
D015220:Calcium Channels; D002147:Calmodulin; D000252:Calcium-Transporting ATPases; D002118:Calcium