The <i>SLENDER</i> Gene of Pea Encodes a Gibberellin 2-Oxidase

Martin, David; Proebsting, William M.; Hedden, Peter

doi:10.1104/pp.121.3.775

Cited by 125 publications

(109 citation statements)

References 17 publications

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“…4) and was observed in several other plant species (for review, see Hedden and Phillips, 2000;Fleet and Sun, 2005). A positive feed-forward regulation as reported for GA 2-oxidase transcript levels from some other plant species (Martin et al, 1999;Thomas et al, 1999;Elliott et al, 2001) was not observed for CmGA2ox1 gene expression, similar to observations obtained with rice GA 2-oxidase (Sakamoto et al, 2001).…”

Section: Discussionsupporting

confidence: 71%

“…There is growing evidence for the presence of rootbased GA biosynthesis from many plant species, including pumpkin (Yamaguchi et al, 1996;Smith et al, 1998), pea (Pisum sativum; Lester et al, 1999;Martin et al, 1999;Elliott et al, 2001;Davidson et al, 2003Davidson et al, , 2004, Arabidopsis (Chiang et al, 1995;Silverstone et al, 1997;Thomas et al, 1999), and rice (Oryza sativa; Sakamoto et al, 2001Sakamoto et al, , 2004Monna et al, 2002;Sasaki et al, 2002;Kaneko et al, 2003;Itoh et al, 2004). In this study, we present direct evidence for GA biosynthesis in root tips of young pumpkin seedlings.…”

Section: Discussionmentioning

confidence: 54%

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Gibberellin Biosynthesis in Developing Pumpkin Seedlings

et al. 2005

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A gibberellin (GA) biosynthetic pathway was discovered operating in root tips of 7-d-old pumpkin (Cucurbita maxima) seedlings. Stepwise analysis of GA metabolism in cell-free systems revealed the conversion of GA 12 -aldehyde to bioactive GA 4 and inactive GA 34 . Highest levels of endogenous GA 4 and GA 34 were found in hypocotyls and root tips of 3-d-old seedlings. cDNA molecules encoding two GA oxidases, CmGA20ox3 and CmGA3ox3, were isolated from root tips of 7-d-old LAB150978-treated seedlings. Recombinant CmGA20ox3 fusion protein converted GA 12 to GA 9 , GA 24 to GA 9 , GA 14 to GA 4 , and, less efficiently, GA 53 to GA 20 , and recombinant CmGA3ox3 protein oxidized GA 9 to GA 4 . Transcript profiles were determined for four GA oxidase genes from pumpkin revealing relatively high transcript levels for CmGA7ox in shoot tips and cotyledons, for CmGA20ox3 in shoot tips and hypocotyls, and for CmGA3ox3 in hypocotyls and roots of 3-d-old seedlings. Transcripts of CmGA2ox1 were mainly found in roots of 7-d-old seedlings. In roots of 7-d-old seedlings, transcripts of CmGA7ox, CmGA20ox3, and CmGA3ox3 were localized in the cap and the rhizodermis by in situ hybridization. We conclude that hypocotyls and root tips are important sites of GA biosynthesis in the developing pumpkin seedling.Gibberellins (GAs) are signaling molecules that regulate and integrate developmental processes during the entire life cycle of higher plants, including shoot elongation and root development (Richards et al., 2001;Olszewski et al., 2002;Fu and Harberd, 2003;Reid et al., 2004;Sun, 2004).GA biosynthetic pathways are of considerable complexity (for review, see Hedden and Kamiya, 1997;Sponsel and Hedden, 2004). They are divided into nonhydroxylated, 3b-hydroxylated, and 13-hydroxylated pathways (Fig. 1, A -C, respectively;Graebe, 1987). A principal pathway to GA plant hormones can be drawn from GA 12 -aldehyde. First, 7-oxidation of GA 12 -aldehyde results in the formation of GA 12 . GA 53 is often formed by 13-hydroxylation of GA 12 . The following three oxidation steps at carbon (C)-20 are catalyzed by one enzyme, the GA 20-oxidase, which, in general, leads to the formation of a C 19 -GA (e.g. GA 9 and GA 20 ; Fig. 1). Alternatively, C-20 oxidation leads to the formation of a carboxylic acid (e.g. GA 25 and GA 17 ). The resulting C 20 -GAs usually are minor products of GA 20-oxidase activity. Finally, 3-oxidation produces GA plant hormones (GA 4 and GA 1 ), which are subsequently inactivated by 2-oxidation (GA 34 and GA 8 ; Fig. 1). In many plant species, 7-oxidation and 13-hydroxylation are catalyzed by NADPH-dependent cytochrome P450 mono-oxygenases. In Arabidopsis (Arabidopsis thaliana), a multifunctional ent-kaurenoic acid oxidase with 7-oxidation catalytic properties has been characterized (Helliwell et al., 2001). In pumpkin (Cucurbita maxima), however, 7-oxidation is catalyzed by an additional multifunctional GA 7-oxidase that belongs to the class of 2-oxoglutarate-dependent dioxygenases (Lange, 1997). Recently, recombinant pumpk...

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Section: Discussionsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 54%

Gibberellin Biosynthesis in Developing Pumpkin Seedlings

et al. 2005

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“…The pea (Pisum sativum) slender mutant contains a loss-of-function allele of a GA2ox gene, GA2ox1, that is normally active in developing seeds: mature seeds of the mutant have increased levels of GA 20 , which, after germination, is activated by 3b-hydroxylation, resulting in increased elongation of the seedling (Reid et al, 1992;Ross et al, 1993Ross et al, , 1995Lester et al, 1999;Martin et al, 1999). Loss of function of the Arabidopsis GA2ox2 gene increases GA 4 levels in dark-imbibed seeds and thereby promotes germination in the mutant (Yamauchi et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

“…Biochemical characterization of the enzymes responsible for 2b-hydroxylation showed that, like the GA 20-oxidases and GA 3-oxidases, they belong to the soluble 2-oxoglutarate-dependent dioxygenase class (Griggs et al, 1991). Genes encoding GA 2-oxidases were first identified by screening cDNA expression libraries for 2b-hydroxylase activity (Lester et al, 1999;Martin et al, 1999;Thomas et al, 1999). Five Arabidopsis GA 2-oxidase genes (GA2ox1, -2, -3, -4, and -6; GA2ox5, At3g17203, is a pseudogene) have since been identified based on sequence homology, and their encoded enzyme activities have been confirmed by heterologous expression in Escherichia coli (Thomas et al, 1999;Hedden and Phillips, 2000;Wang et al, 2004;Jasinski et al, 2005), demonstrating that they were active against C 19 -GAs, such as the bioactive GAs, GA 4 and GA 1 , and their immediate precursors.…”

Section: Introductionmentioning

confidence: 99%

Genetic Analysis Reveals That C19-GA 2-Oxidation Is a Major Gibberellin Inactivation Pathway inArabidopsis

et al. 2008

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Bioactive hormone concentrations are regulated both at the level of hormone synthesis and through controlled inactivation. Based on the ubiquitous presence of 2β-hydroxylated gibberellins (GAs), a major inactivating pathway for the plant hormone GA seems to be via GA 2-oxidation. In this study, we used various approaches to determine the role of C19-GA 2-oxidation in regulating GA concentration and GA-responsive plant growth and development. We show that Arabidopsis thaliana has five C19-GA 2-oxidases, transcripts for one or more of which are present in all organs and at all stages of development examined. Expression of four of the five genes is subject to feed-forward regulation. By knocking out all five Arabidopsis C19-GA 2-oxidases, we show that C19-GA 2-oxidation limits bioactive GA content and regulates plant development at various stages during the plant life cycle: C19-GA 2-oxidases prevent seed germination in the absence of light and cold stimuli, delay the vegetative and floral phase transitions, limit the number of flowers produced per inflorescence, and suppress elongation of the pistil prior to fertilization. Under GA-limited conditions, further roles are revealed, such as limiting elongation of the main stem and side shoots. We conclude that C19-GA 2-oxidation is a major GA inactivation pathway regulating development in Arabidopsis.

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“…By contrast, a recently characterized class of GA-catabolizing enzymes, the GA 2-oxidases, are involved in the irreversible conversion of active GAs and their precursors to inactive forms and potentially can be used to reduce the endogenous levels of active GAs. cDNAs that encode 2-oxidases were isolated recently from runner bean, Arabidopsis, pea, and rice (MacMillan et al, 1997;Lester et al, 1999;Martin et al, 1999;Thomas et al, 1999;Sakamoto et al, 2001) and shown to perform oxidation reactions at carbon 2 of various biologically active and inactive GAs in vitro. In addition, several ESTs from lotus, Medicago , maize, soybean, and tomato, and sequences from the Arabidopsis and rice genome-sequencing projects, have been identified as putative GA 2-oxidases (Elliott et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Gibberellins Are Required for Seed Development and Pollen Tube Growth in Arabidopsis

2002

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Gibberellins (GAs) are tetracyclic diterpenoids that are essential endogenous regulators of plant growth and development. GA levels within the plant are regulated by a homeostatic mechanism that includes changes in the expression of a family of GA-inactivating enzymes known as GA 2-oxidases. Ectopic expression of a pea GA 2-oxidase2 cDNA caused seed abortion in Arabidopsis, extending and confirming previous observations obtained with GA-deficient mutants of pea, suggesting that GAs have an essential role in seed development. A new physiological role for GAs in pollen tube growth in vivo also has been identified. The growth of pollen tubes carrying the 35S:2ox2 transgene was reduced relative to that of nontransgenic pollen, and this phenotype could be reversed partially by GA application in vitro or by combining with spy-5 , a mutation that increases GA response. Treatment of wild-type pollen tubes with an inhibitor of GA biosynthesis in vitro also suggested that GAs are required for normal pollen tube growth. These results extend the known physiological roles of GAs in Arabidopsis development and suggest that GAs are required for normal pollen tube growth, a physiological role for GAs that has not been established previously.

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The SLENDER Gene of Pea Encodes a Gibberellin 2-Oxidase

Cited by 125 publications

References 17 publications

Gibberellin Biosynthesis in Developing Pumpkin Seedlings

Gibberellin Biosynthesis in Developing Pumpkin Seedlings

Genetic Analysis Reveals That C19-GA 2-Oxidation Is a Major Gibberellin Inactivation Pathway inArabidopsis

Gibberellins Are Required for Seed Development and Pollen Tube Growth in Arabidopsis

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