- The rice Os03g0856700 was first reported as OsGA20ox1 in 2004 by the researchers from Japan .
OsGA20ox1, encoding an isoform of gibberellin 20-oxidase, for regulation of plant stature in rice. Gibberellin (GA) 20-oxidase (GA20ox) is a key enzyme that normally catalyzes the penultimate steps in GA biosynthesis.
- Figure 1 shows the gross morphology of the wild type and mutant plants. A mutant, B142, tagged with a T-DNA containing three CaMV 35S promoters showed a tall, GA-overproduction phenotype.The integrated T-DNAs, which contain three CaMV 35S promoters, are located upstream of the OsGA20ox1 open reading frame (ORF) in the B142 mutant genome. The ﬁnal stature of the B142 mutant reﬂects internode overgrowth and is approximately twice that of its wild-type parent.
- Figure 2 shows a typical phenotype of a rice GA deﬁcient mutant at the young seedling stage. The GA-related mutants showed dwarﬁsm without the induction of additionally aberrantmorphology. The ﬁnal plant height of GA-deﬁcient mutants ranged widely between \5% and 90% of the wild-type plants. The leaf blades of the mutant plants became dark green, shorter, and wider than those of the wild-type plants.
Semiquantitative reverse transcription (RT)-PCR analysis revealed that OsGA20ox1 were expressed at different levels in various organs of wild-type rice(Fig. 3). OsGA20ox1 were simultaneously expressed in all vegetative organs of rice, and all OsGA20ox genes were expressed in the reproductive organs. This overlap expression pattern, accompanied with the feedback up-regulation of other GA biosynthetic enzymes by the homeostatic system, compensate the defect in OsGA20ox2 function in shoot elongation, and consequently the defect in OsGA20ox2/SD1 induces suitable semidwarﬁsm of the rice height for useful breeding.
Figure 4 shows that phylogenetic analysis of 2ODDs (GA20ox, GA3ox, and GA2ox) revealed that the GA20ox proteins from dicot plants shared higher amino acid identity each other (49%–80% identities) and formed a single group. OsGA20ox2 showed higher similarity (61% identity) to OsGA20ox4 than the other OsGA20ox proteins, and OsGA20ox2 and OsGA20ox4 formed one subgroup (36%–48% identities with dicot proteins), whereas OsGA20ox1 and OsGA20ox3 were separately located from the OsGA20ox2/OsGA20ox4 subgroup (39%–54% and 39%–49% identities with dicot proteins, respectively).
The GAs form a large family of tetracyclic diterpenoid phytohormones that are involved in the regulation of various growth and developmental processes in higher plants. Bioactive GAs, such as GA1 and GA4,are synthesized from trans-geranylgeranyl diphosphate (GGDP) as shown in Figure 5.
Labs working on this gene
- Laboratory of Bio-control, Graduate School of Natural Science and Technology, Niigata University, 2-8050 Ikarashi, Niigata 950-2181, Japan
- Department of Genetics and Physiology, National Institute of Floricultural Science, 2-1, Fujimoto, Tsukuba, Ibaraki 305-8519, Japan;
- Faculty of Agriculture, Niigata University, 2-8050 Ikarashi, Niigata 950-2181, Japan;
- Department of Rice Research, National Agricultural Research Center (NARC), 1-2-1, Inada, Jo-etsu, Niigata 943-0193, Japan
- Field Production Science Center, University of Tokyo, Nishi-Tokyo, Tokyo 188–0002, Japan
- Bioscience and Biotechnology Center, Nagoya University, Nagoya, Aichi 464–8601, Japan
- BioResource Center, RIKEN Tsukuba Institute, Tsukuba, Ibaraki 305–0074, Japan
- Molecular Genetics Department, National Institute of Agrobiological Sciences,Tsukuba, Ibaraki 305–8602, Japan.
- Oikawa T, Koshioka M, Kojima K, et al. A role of OsGA20ox1, encoding an isoform of gibberellin 20-oxidase, for regulation of plant stature in rice[J]. Plant molecular biology, 2004, 55(5): 687-700.PMID 15604710
- Sakamoto T, Miura K, Itoh H, et al. An overview of gibberellin metabolism enzyme genes and their related mutants in rice[J]. Plant Physiology, 2004, 134(4): 1642-1653.PMID 15075394
- Hedden P, Phillips A L. Gibberellin metabolism: new insights revealed by the genes[J]. Trends in plant science, 2000, 5(12): 523-530.PMID 11120474
- Hedden P, Kamiya Y. GIBBERELLIN BIOSYNTHESIS: Enzymes, Genes and Their Regulation[J]. Annu. Rev. Plant Physiol. Plant Mol. Biol, 1997, 48: 431-60.PMID 15012270