Isolation of the Arabidopsis GA4 Locus

Abstract

Y.Tsujimoto and T.Numaga contributed equally to this work The tom2-1 mutation of Arabidopsis thaliana reduces the ef®ciency of intracellular multiplication of toba-moviruses. The tom2-1 mutant was derived from fast-neutron-irradiated seeds, and the original mutant line also carries ttm1, a dominant modi®er that increases tobamovirus multiplication ef®ciency in a tobamo-virus-strain-speci®c manner in the tom2-1 genetic background. Here, we show that the tom2-1 mutation involved a deletion of ~20 kb in the nuclear genome. The deleted region included two genes named TOM2A and TOM2B that were both associated with the tom2-1 phenotype, whereas ttm1 corresponded to the trans-location of part of the deleted region that included intact TOM2B but not TOM2A. TOM2A encodes a 280 amino acid putative four-pass transmembrane protein with a C-terminal farnesylation signal, while TOM2B encodes a 122 amino acid basic protein. The split-ubi-quitin assay demonstrated an interaction of TOM2A both with itself and with TOM1, an integral membrane protein of A.thaliana presumed to be an essential constituent of tobamovirus replication complex. The data presented here suggest that TOM2A is also an integral part of the tobamovirus replication complex.

Extragenic Suppressors of the Arabidopsis gaiMutation Alter the Dose-Response Relationship of Diverse Gibberellin Responses1

“…Recent experiments have shown that in normal plants endogenous GA levels are homeostatically controlled via GA-mediated negative feedback regulation (Hedden and Croker, 1992). As a part of this process, the expression of a number of the genes encoding enzymes involved in GA biosynthesis is downregulated by GA (Chiang et al, 1995;Phillips et al, 1995;Xu et al, 1995;Martin et al, 1996;Hedden and Kamiya, 1997;Cowling et al, 1998). This down-regulation is perturbed in gai (Talon et al, 1990a;Xu et al, 1995;Peng et al, 1997), thus explaining the increased endogenous GA levels in gai and indicating the involvement of GAI (the GAI gene product) in the homeostatic regulation of GA levels.…”

Cloning and Overproduction of Gibberellin 3-Oxidase in Hybrid Aspen Trees. Effects on Gibberellin Homeostasis and Development

“…The expression of the Arabidopsis homologs has been demonstrated to be feedback and feed-forward regulated by bioactive GAs, respectively (Chiang et al, 1995;Phillips et al, 1995;Xu et al, 1995;Thomas et al, 1999) and previously both PttGA20ox1 and PttGA3ox1 have been shown to be feedback regulated in hybrid aspen (Eriksson and Moritz, 2002;M. Chono, unpublished data).…”

“…In addition, a large number of studies have found evidence that GA biosynthesis is finely modulated via regulation of the GA dioxygenases. Work on GA mutants and plants treated with chemical inhibitors of GA biosynthesis has shown that transcript levels of GA20ox and GA3ox increase, while GA2ox transcripts decrease, in response to lowered amounts of GA (Chiang et al, 1995;Phillips et al, 1995; Thomas et al, 1 Article, publication date, and citation information can be found at www.plantphysiol.org/cgi …”

Genetic Characterization and Functional Analysis of the GID1 Gibberellin Receptors inArabidopsis

“…This involves downregulation of some of the GA-biosynthetic genes encoding GA 20-oxidase (GA20ox) and GA 3-oxidase (GA3ox) and upregulation of genes encoding GA 2-oxidase (Hedden and Phillips, 2000;Olszewski et al, 2002). We investigated GA responsiveness of the gid1a-1 gid1b-1 gid1c-1 mutant at the molecular level by examining expression of GA3ox1 (Chiang et al, 1995) using real-time quantitative RT-PCR. Compared with Col-0 seedlings, GA3ox1 transcript levels were elevated approximately sixfold in the triple mutant ( Figure 3E).…”