title: UV-A induces two calcium waves in Physcomitrella patens.
abstract: Our understanding of the role of Ca2+ in blue/UV-A photoreceptor signaling in a single cell is limited. Insight into calcium signaling has now been attained in Physcomitrella patens and its cryptochrome and phototropin knock-outs. Physcomitrella patens caulonemal filaments grow in the dark by apical extension and their apical cells are highly polarized. Fura-2-dextran ratio images of the apical cell from wild type (WT), Ppcry1a/1b and PpphotA2/B1/B2 were obtained immediately following UV-A exposure (30 microW cm(-2) at 340 nm for 1,000 ms plus 30 microW cm(-2) at 380 nm for 1,000 ms) [abbreviated as 1,000 ms (340/380 nm)] and demonstrated two intracellular waves: a Ca2+ wave from the growing apical tip through the apical cap, and a wave from the junction of the neighboring cell through the vacuolar, nuclear and plastid regions. In WT, the UV-A-induced tip wave increase had a magnitude of 454.0 +/- 40 nM, traveled at a rate of 3.4 +/- 0.7 microm s(-1) and was complete within 26.6 +/- 2.3 s, while the basal vacuolar wave had a magnitude of 596.8 +/- 110 nM, a rate of 8.4 +/- 0.8 microm s(-1) and duration of 25.3 +/- 4.9 s. Subsequent Ca2+ spikes of similar magnitude followed these waves. The amplitude of the Ca2+ waves in the apical cap and basal vacuolar regions of Ppcry1a/1b were higher than those in the WT, while the duration of those in PpphotA2/B1/B2 was longer. Subsequent Ca2+ spikes occurred in WT and Ppcry1a/1b but not in PpphotA2/B1/B2. When Mn2+ was added to the culture medium, the [Ca2+](cyt) increase was delayed, did not move as a wave and lasted longer. The results indicate that plants respond to blue light and UV-A radiation by generating a wave of changes in the [Ca2+](cyt). The characteristics of these Ca2+ waves were dependent upon cryptochrome and phototropin. Blue/UV-A signaling in P. patens appears to differ from that in Arabidopsis.
authors.affiliation: Natural Science Department, Baruch College, City University of New York, 17 Lexington Avenue, New York, NY 10010, USA. edward_tucker@baruch.cuny.edu
authors.forename: Edward B
authors.initials: EB
authors.lastname: Tucker
authors.forename: Michelle
authors.initials: M
authors.lastname: Lee
authors.forename: Shaan
authors.initials: S
authors.lastname: Alli
authors.forename: Vinoud
authors.initials: V
authors.lastname: Sookhdeo
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Wada
authors.forename: Takato
authors.initials: T
authors.lastname: Imaizumi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kasahara
authors.forename: Peter K
authors.initials: PK
authors.lastname: Hepler
mesh_terms: D019068:Bryopsida / Q000378:metabolism / Q000528:radiation effects*; D002118:Calcium / Q000378:metabolism*; D056931:Cryptochromes; D005420:Flavoproteins / Q000502:physiology; D008854:Microscopy, Electron; D014466:Ultraviolet Rays
chemical_list: D056931:Cryptochromes; D005420:Flavoproteins; D002118:Calcium