Feed-back regulation of gibberellin biosynthesis and gene expression in Pisum sativum L.

Dn, Martin; Wm, Proebsting; Td, Parks; Wg, Dougherty; Lange, Theodor; Mj, Lewis; Gaskin, Paul; Hedden, Peter

doi:10.1007/bf00208304

Cited by 107 publications

(100 citation statements)

References 23 publications

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“…In the DELLA slender mutants sln in barley , slr1 in rice (Itoh et al, 2002), and la cry-s in pea (Potts et al, 1985;Martin et al, 1996), the synthesis of bioactive GAs is reduced, but this has only been shown for shoots. We therefore monitored the expression of GA biosynthesis and deactivation genes in the roots of wild-type and slender pea plants.…”

Section: Discussionmentioning

confidence: 99%

The Pea DELLA Proteins LA and CRY Are Important Regulators of Gibberellin Synthesis and Root Growth

et al. 2008

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The theory that bioactive gibberellins (GAs) act as inhibitors of inhibitors of plant growth was based originally on the slender pea (Pisum sativum) mutant (genotype la cry-s), but the molecular nature of this mutant has remained obscure. Here we show that the genes LA and CRY encode DELLA proteins, previously characterized in other species (Arabidopsis [Arabidopsis thaliana] and several grasses) as repressors of growth, which are destabilized by GAs. Mutations la and cry-s encode nonfunctional proteins, accounting for the fact that la cry-s plants are extremely elongated, or slender. We use the la and cry-s mutations to show that in roots, DELLA proteins effectively promote the expression of GA synthesis genes, as well as inhibit elongation. We show also that one of the DELLAregulated genes is a second member of the pea GA 3-oxidase family, and that this gene appears to play a major role in pea roots.It is well known that primary root growth is strongly influenced by the plant hormone GA (Davies, 2004). For example, the application of bioactive GA to roots treated with the growth inhibitor ancymidol completely restored growth to that of the untreated plants (Tanimoto, 1991). Yaxley et al. (2001) established the importance of GAs for root growth in peas (Pisum sativum) by using a variety of GA-deficient mutant plants. In the na-1 mutant, for example, root GA 1 levels, and root elongation, were significantly reduced compared with wild-type plants, and when the GA 1 content was restored to wild-type levels, so too was root elongation.The GAs act by destabilizing the growth inhibitory DELLA proteins (Peng et al., 1997;Harberd et al., 1998;Silverstone et al., 2001;Alvey and Harberd, 2005). In other words, GA acts as an ''inhibitor of an inhibitor '' (Harberd et al., 1998). Interestingly, there is also evidence that DELLA proteins promote the biosynthesis of active GAs. For example, in the Arabidopsis (Arabidopsis thaliana) DELLA mutant rga, the expression of the biosynthesis gene GA4 is reduced, indicating that high DELLA protein levels are associated with an up-regulation of GA synthesis genes (Silverstone et al., 2001 (Silverstone et al., 1998;Gubler et al., 2002). However, the available evidence indicates greater redundancy in dicots compared with monocots (Ikeda et al., 2001;Thomas and Hedden, 2006). There have been five DELLA genes isolated from Arabidopsis (GAI, RGA, RGL1, RGL2, and RGL3), yet only one in rice (SLR1), barley (SLN1), and maize (Zea mays; D8; Peng et al., 1997Peng et al., , 1999Silverstone et al., 1998;Ikeda et al., 2001;Chandler et al., 2002;Gubler et al., 2002), with the possibility of another DELLA gene in maize (D9; accession no. ABI84225). It should be noted, however, that DELLAs have been studied in fewer dicot model species than in monocot species. To date, DELLA-encoding genes from pea have not been reported, even though observations on the slender phenotype of pea triggered the early suggestion that GA acts an inhibitor of an inhibitor (Brian, 1957). The elongated slender phenotype, con...

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Section: Discussionmentioning

confidence: 99%

The Pea DELLA Proteins LA and CRY Are Important Regulators of Gibberellin Synthesis and Root Growth

et al. 2008

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“…With regard to the regulation of elongation growth (described above), it has been suggested that Pfr might suppress GA biosynthesis. GA 20-oxidase transcript levels are subject to feedback regulation (Phillips et al, 1995;Martin et al, 1996;Toyomasu et al, 1997); GAdeficient mutants accumulate a high level of 20-oxidase mRNA, which is markedly reduced by application of bioactive GA. Our preliminary experiments showed that, similar to Ls20ox2, the expression of the Ls20ox1 and Ls3h1 genes, which were not negatively regulated by far-red-/ red-light treatment, was markedly decreased by treatment with GA 1 (data not shown). Furthermore, we cannot yet say whether the endogenous GA 1 generated within 3 h of incubation after a far-red-/red-light treatment is sufficient for negative feedback regulation to achieve the observed decrease in the Ls20ox2 transcript levels.…”

Section: Discussionmentioning

confidence: 99%

“…Ps074 (no. X91658) (Martin et al, 1996), At2301 (no. X83379) (Phillips et al, 1995), and Cm20ox (no.…”

Section: Northern-blot Analysismentioning

confidence: 99%

Phytochrome Regulates Gibberellin Biosynthesis during Germination of Photoblastic Lettuce Seeds

et al. 1998

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Germination of lettuce (Lactuca sativa L.) seed is regulated by phytochrome. The requirement for red light is circumvented by the application of gibberellin (GA). We have previously shown that the endogenous content of GA 1 , the main bioactive GA in lettuce seeds, increases after red-light treatment. To clarify which step of GA 1 synthesis is regulated by phytochrome, cDNAs encoding GA 20-oxidases (Ls20ox1 and Ls20ox2, for L. sativa GA 20-oxidase) and 3␤-hydroxylases (Ls3h1 and Ls3h2 for L. sativa GA 3␤-hydroxylase) were isolated from lettuce seeds by reverse-transcription polymerase chain reaction. Functional analysis of recombinant proteins expressed in Escherichia coli confirmed that the Ls20ox and Ls3h encode GA 20-oxidases and 3␤-hydroxylases, respectively. Northern-blot analysis showed that Ls3h1 expression was dramatically induced by red-light treatment within 2 h, and that this effect was canceled by a subsequent far-red-light treatment. Ls3h2 mRNA was not detected in seeds that had been allowed to imbibe under any light conditions. Expression of the two Ls20ox genes was induced by initial imbibition alone in the dark. The level of Ls20ox2 mRNA decreased after the red-light treatment, whereas that of Ls20ox1 was unaffected by light. These results suggest that red light promotes GA 1 synthesis in lettuce seeds by inducing Ls3h1 expression via phytochrome action.

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“…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.…”

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confidence: 99%

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

et al. 1999

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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 gar2-1 affect 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.

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Feed-back regulation of gibberellin biosynthesis and gene expression in Pisum sativum L.

Cited by 107 publications

References 23 publications

The Pea DELLA Proteins LA and CRY Are Important Regulators of Gibberellin Synthesis and Root Growth

The Pea DELLA Proteins LA and CRY Are Important Regulators of Gibberellin Synthesis and Root Growth

Phytochrome Regulates Gibberellin Biosynthesis during Germination of Photoblastic Lettuce Seeds

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

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