Auxin Regulation of the Gibberellin Pathway in Pea

O'Neill, Damian; Ross, John J.

doi:10.1104/pp.010587

Cited by 131 publications

(89 citation statements)

References 34 publications

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“…Developing pea seeds contain a modified auxin, 4Cl-IAA, which has been proposed to move from the seed, via the funiculus, to the surrounding pericarp tissue where it promotes GA biosynthesis and hence fruit growth (Ozga et al 2002(Ozga et al , 2003. This model is also supported by studies in elongating internodes of pea and other species in which apically derived auxin promotes the production of active GAs (Ross and O'Neill 2001;O'Neill and Ross 2002). Genetics is a powerful technique for investigating plant physiology, including reproductive development in general and fruit growth in particular.…”

Section: Introductionsupporting

confidence: 53%

Localised and non-localised promotion of fruit development by seeds in Arabidopsis

Cox¹,

Swain²

2006

Functional Plant Biol.

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Abstract. In Arabidopsis, as in the majority of flowering plants, developing seeds promote fruit growth. One method to investigate this interaction is to use plants with reduced seed set and determine the effect on fruit growth. Plants homozygous for a transgene designed to ectopically express a gene encoding a gibberellin-deactivating enzyme exhibit reduced pollen tube elongation, suggesting that the plant hormone gibberellin is required for this process. Reduced pollen tube growth causes reduced seed set and decreased silique (fruit) size, and this genotype is used to explore the relationship between seed set and fruit elongation. A detailed analysis of seed set in the transgenic line reveals that reduced pollen tube growth decreases the probability of each ovule being fertilised. This effect becomes progressively more severe as the distance between the stigma and the ovule increases, revealing the complex biology underlying seed fertilisation. In terms of seed-promoted fruit growth, major localised and minor non-localised components that contribute to final silique length can be identified. This result demonstrates that despite the relatively small size of the fruit and associated structures, Arabidopsis can be used as a model to investigate fundamental questions in fruit physiology.

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Section: Introductionsupporting

confidence: 53%

Localised and non-localised promotion of fruit development by seeds in Arabidopsis

Cox¹,

Swain²

2006

Functional Plant Biol.

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“…After the divergence of the 2-oxidases, modification occurred such that at least some members of this group are now downregulated, not upregulated, by the level of auxin normally found in the plant. Interestingly, the putative ancestral condition (upregulation by normal auxin levels) can still be observed for some 2-oxidase genes in some circumstances (O'Neill and Ross 2002). A similar scenario might also apply in the case of the DELLA proteins, which mediate the capacity of bioactive GA to downregulate its synthesis and to upregulate its deactivation.…”

Section: Regulation Of Ga Levels By Auxin and By Ga Signallingmentioning

confidence: 94%

Evolution of growth-promoting plant hormones

Ross

Reid

2010

Functional Plant Biol.

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Abstract. The plant growth hormones auxin, gibberellins (GAs) and brassinosteroids (BRs) are major determinants of plant growth and development. Recently, key signalling components for these hormones have been identified in vascular plants and, at least for the GAs and BRs, biosynthetic pathways have been clarified. The genome sequencing of a range of species, including a few non-flowering plants, has allowed insight into the evolution of the hormone systems. It appears that the moss Physcomitrella patens can respond to auxin and contains key elements of the auxin signalling pathway, although there is some doubt as to whether it shows a fully developed rapid auxin response. On the other hand, P. patens does not show a GA response, even though it contains genes for components of GA signalling. The GA response system appears to be more advanced in the lycophyte Selaginella moellendorffii than in P. patens. Signalling systems for BRs probably arose after the evolutionary divergence of the mosses and vascular plants, although detailed information is limited. Certainly, the processes affected by the growth hormones (e.g. GAs) can differ in the different plant groups, and there is evidence that with the evolution of the angiosperms, the hormone systems have become more complex at the gene level. The intermediate nature of mosses in terms of overall hormone biology allows us to speculate about the possible relationship between the evolution of plant growth hormones and the evolution of terrestrial vascular plants in general.

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“…2A). The genes encoding most of the enzymes involved in GA biosynthesis have been isolated (Hedden and Phillips, 2000;Olszewski et al, 2002;O'Neill and Ross, 2002;Ogawa et al, 2003). We analyzed the expression levels of 12 GA-biosynthetic genes in siliques of wildtype, lec2-1, and fus3-8 mutants using real-time RT-PCR (see ''Materials and Methods'' for a complete list).…”

Section: Resultsmentioning

confidence: 99%

AtGA3ox2, a Key Gene Responsible for Bioactive Gibberellin Biosynthesis, Is Regulated during Embryogenesis by LEAFY COTYLEDON2 and FUSCA3 in Arabidopsis

et al. 2004

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Embryonic regulators LEC2 (LEAFY COTYLEDON2) and FUS3 (FUSCA3) are involved in multiple aspects of Arabidopsis (Arabidopsis thaliana) seed development, including repression of leaf traits and premature germination and activation of seed storage protein genes. In this study, we show that gibberellin (GA) hormone biosynthesis is regulated by LEC2 and FUS3 pathways. The level of bioactive GAs is increased in immature seeds of lec2 and fus3 mutants relative to wild-type level. In addition, we show that the formation of ectopic trichome cells on lec2 and fus3 embryos is a GA-dependent process as in true leaves, suggesting that the GA pathway is misactivated in embryonic mutants. We next demonstrate that the GA-biosynthesis gene AtGA3ox2, which encodes the key enzyme AtGA3ox2 that catalyzes the conversion of inactive to bioactive GAs, is ectopically activated in embryos of the two mutants. Interestingly, both b-glucuronidase reporter gene expression and in situ hybridization indicate that FUS3 represses AtGA3ox2 expression mainly in epidermal cells of embryo axis, which is distinct from AtGA3ox2 pattern at germination. Finally, we show that the FUS3 protein physically interacts with two RY elements (CATGCATG) present in the AtGA3ox2 promoter. This work suggests that GA biosynthesis is directly controlled by embryonic regulators during Arabidopsis embryonic development.Higher plant embryogenesis is divided into two major phases: embryo development (or morphogenesis) and seed maturation (West and Harada, 1993). During embryo development, early morphogenetic processes occur that give rise to embryonic cell types, tissues, and organs. During seed maturation, the fully developed embryo undergoes maturation, during which food reserves accumulate and dormancy and desiccation tolerance develop.Seed development has been extensively studied in Arabidopsis (Arabidopsis thaliana) using mutants defective either in morphogenesis, such as GNOM (Mayer et al., 1991;Shevell et al., 1994) or KNOLLE (Mayer et al., 1991;Lukowitz et al., 1996), or in maturation, such as ABI (ABSCISIC ACID-INSENSITIVE) loci that were initially identified on the basis of the abscisic acid (ABA) hormone-resistant germination of mutants at these loci (Koornneef et al., 1984;Giraudat et al., 1992;Finkelstein et al., 1998;Finkelstein and Lynch, 2000). A particular set of mutants exhibiting the lec phenotype, which consists of a partial transformation of cotyledons into leaves, has allowed the identification of an important network of regulatory genes. The LEC1 (LEAFY COTYLEDON1; Meinke, 1992), LEC2 (Meinke et al., 1994), and FUS3 (FUSCA3;Keith et al., 1994;Meinke et al., 1994) genes, which are defined as the LEC genes hereafter, are the only known regulators required for normal development during both the morphogenesis and the maturation phases (Holdsworth et al., 1999;Harada, 2001 Article, publication date, and citation information can be found at www.plantphysiol.org/cgi

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Auxin Regulation of the Gibberellin Pathway in Pea

Cited by 131 publications

References 34 publications

Localised and non-localised promotion of fruit development by seeds in Arabidopsis

Localised and non-localised promotion of fruit development by seeds in Arabidopsis

Evolution of growth-promoting plant hormones

AtGA3ox2, a Key Gene Responsible for Bioactive Gibberellin Biosynthesis, Is Regulated during Embryogenesis by LEAFY COTYLEDON2 and FUSCA3 in Arabidopsis

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