Phytochrome A-mediated inhibition of seed germination in tomato

Abstract

Far-red light (FR) inhibition of seed germination of tomato (Solanum lycopersicum L.) was studied with the phytochrome (phy)-hypersensitive mutants, hp-1w, hp-1w,fri1, a phyA-deficient double mutant, and hp-1w,tri1, a phyB1-deficient double mutant. Seeds of all mutants germinated readily in the dark at 25 degrees C, and the germination was retarded by a single 100-s FR pulse given 1-3 h after sowing. The effect of an FR pulse was red-light reversible in all mutants used. After 24 h where a single FR pulse was no longer effective, prolonged FR exposure or hourly FR pulses suppressed germination in hp-1w and hp-1w,tri1, whereas in hp-1w,fri1 the suppressive effect of FR was almost absent. The effect of the prolonged FR was greater than that of the hourly 3-min FR pulses having equal photon fluence, and was fluencerate dependent. Thus we conclude that the germination inhibition by FR in tomato seed consists of a low-fluence response and a high irradiance response (HIR); the latter is controlled by phyA, but not phyB1. This is the first indication of phyA being involved in the HIR of seed germination inhibition.

Light exaggerates apical hook curvature through phytochrome actions in tomato seedlings

“…The details of these light sources were already described (Shichijo et al 1993(Shichijo et al , 2001Shichijo and Hashimoto 1997). When necessary, fluence rate was adjusted with neutral filter (Fujitoku Corp., Tokyo, Japan) (Shichijo et al 1999).…”

“…Later the HP-1 was identified as UV-DAMAGED DNA BIND-ING PROTEIN-1 (DDB1), which is an essential component of CUL4-based E3 ligase complex that repress some phytochrome actions (Lieberman et al 2004;Liu et al 2004;Bernhardt et al 2006;Chen et al 2006;Wang et al 2008). In the hp-1/ddb1 background, the roles of phyA or phyB1 have been easily distinguished from those of the others (Kerckhoffs et al 1997a, b;Weller et al 2000Weller et al , 2001Shichijo et al 2001). In the course of our investigation with these mutants in search of any novel phenomenon related to phytochromes, we encountered the phenomenon that a normal angle size of hook on dark-grown seedlings was enormously exaggerated not only by white light (WL) and R, but also by FR given as a brief pulse (Rp, FRp) or continuously (Rc, FRc).…”

Seed Germination in Tomato: A Focus on Interaction between Phytochromes and Gibberellins or Abscisic Acid

“…However, data regarding how ABA is part of light signaling are still very scarce in tomato. Majority of the currently available information relates to the separate effects of phy [24] [25] or ABA [26] [27].…”

Hormonal and environmental regulation of seed germination in salt cress (Thellungiella halophila)

“…Oryzopsis miliaceae, Sinapis arvensis and Datura ferox (Negbi and Koller 1964;Bartley and Frankland 1982;de Miguel et al 2000;Arana et al 2007). The dual roles of light in seed germination might be mediated by different types of phytochromes (Shinomura et al 1994(Shinomura et al , 1996Shichijo et al 2001;Arana et al 2007). Physiological basis of plant responses to HIR and LFR has not been adequately explored (Arana et al 2007).…”

“…Light (low-fluence response, LFR) and cold stratification promote germination of smaller sized seeds (Bewley and Black 1994;Kigel 1995;Milberg et al 2000), and seed germination in Arabidopsis is mediated through enhanced biosynthesis of gibberellins through red/far red and phytochrome B (Yamaguchi and Kamiya 2002;Yamaguchi et al 2004). Continuous white light (Highirradiance response, HIR) inhibits germination of some species from desert such as Bromus sterilis, B. erectus, Nemophila insignis, Phacelia tanacetifolie, Agriophyllum squarrosum, Artemisia ordosica (Thompson 1989;Bewley and Black 1994;Kigel 1995;Zheng et al 2004Zheng et al , 2005, through the action of phytochrom A (Shichijo et al 2001). Light can both promote and inhibit seed germination of a species under different conditions e.g.…”