RT Journal Article SR Electronic T1 Extragenic Suppressors of the Arabidopsis gaiMutation Alter the Dose-Response Relationship of Diverse Gibberellin Responses JF Plant Physiology JO Plant Physiol. FD American Society of Plant Biologists SP 1199 OP 1208 DO 10.1104/pp.119.4.1199 VO 119 IS 4 A1 Peng, Jinrong A1 Richards, Donald E. A1 Moritz, Thomas A1 Caño-Delgado, Ana A1 Harberd, Nicholas P. YR 1999 UL http://www.plantphysiol.org/content/119/4/1199.abstract AB Active gibberellins (GAs) are endogenous factors that regulate plant growth and development in a dose-dependent fashion. Mutant plants that are GA deficient, or exhibit reduced GA responses, display a characteristic dwarf phenotype. Extragenic suppressor analysis has resulted in the isolation of Arabidopsis mutations, which partially suppress the dwarf phenotype conferred by GA deficiency and reduced GA-response mutations. Here we describe detailed studies of the effects of two of these suppressors,spy-7 and gar2–1, on several different GA-responsive growth processes (seed germination, vegetative growth, stem elongation, chlorophyll accumulation, and flowering) and on the in planta amounts of active and inactive GA species. The results of these experiments show that spy-7 and gar2–1affect the GA dose-response relationship for a wide range of GA responses and suggest that all GA-regulated processes are controlled through a negatively acting GA-signaling pathway. LDlong-day photoperiodPACpaclobutrazolSDshort-day photoperiod