Article

Overexpression of the Arabidopsis gai gene in apple significantly reduces plant size. Plant Cell Rep

Department of Plant Breeding and Biotechnology, Swedish University of Agricultural Sciences, Box 44, 230-53 Alnarp, Sweden.
Plant Cell Reports (Impact Factor: 3.07). 03/2008; 27(2):289-96. DOI: 10.1007/s00299-007-0462-0
Source: PubMed

ABSTRACT

Genetic engineering is an attractive method to obtain dwarf plants in order to eliminate the extensive use of growth retardants in horticultural crop production. In this study, we evaluated the potential of using the Arabidopsis
gai (gibberellic acid insensitive) gene to dwarf apple trees. The gai gene under 35S promoter was introduced in the apple rootstock A2 and the cultivars Gravenstein and McIntosh through Agrobacterium-mediated transformation. One transgenic clone was recovered for Gravenstein and McIntosh, and several transgenic clones for A2, confirmed by Southern blot analysis. Two weak bands were detected by Southern blot analysis in all the untransformed controls, possibly indicating the existence of the internal GAI gene in apple. Most of the transgenic plants showed reduced growth in vitro. Growth analyses in the greenhouse showed a clear reduction in stem length, internode length and node number for the dwarf clones. The normal phenotype of some transgenic clones appears to be associated with silencing of the introduced gai gene, confirmed by RT–PCR analysis. In general, transgenic clones showed reduced rooting ability, especially for the extremely compact ones.

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Available from: Li-Hua Zhu, Jul 24, 2014
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    • "This dwarfing is reversed by GA application (Bulley et al., 2005). The overexpression of wild-type or dominantnegative mutant versions of the DELLA genes repressor of ga1- like (rgl ) and ga insensitive (gai), which act as constitutive GA response repressors, leads to dwarfism in both trees and herbaceous species (Fu et al., 2001; Petty et al., 2003; Zhu et al., 2008; Zawaski et al., 2011). Likewise, a semi-dominant gai allele in grapevine that contains a missense mutation in the essential DELLA repressor domain results in dwarfing, in addition to showing germination defects and premature inflorescence development (Boss & Thomas, 2002). "
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    ABSTRACT: Little is known about the genetic factors controlling tree size and shape. Here, we studied the genetic basis for a recessive brachytic dwarfism trait (dw) in peach (Prunus persica) that has little or no effect on fruit development. A sequencing-based mapping strategy positioned dw on the distal end of chromosome 6. Further sequence analysis and fine mapping identified a candidate gene for dw as a non-functional allele of the gibberellic acid receptor GID1c. Expression of the two GID1-like genes found in peach, PpeGID1c and PpeGID1b, was analyzed. GID1c was predominantly expressed in actively growing vegetative tissues, whereas GID1b was more highly expressed in reproductive tissues. Silencing of GID1c in plum via transgenic expression of a hairpin construct led to a dwarf phenotype similar to that of dw/dw peaches. In general, the degree of GID1c silencing corresponded to the degree of dwarfing. The results suggest that PpeGID1c serves a primary role in vegetative growth and elongation, whereas GID1b probably functions to regulate gibberellic acid perception in reproductive organs. Modification of GID1c expression could provide a rational approach to control tree size without impairing fruit development.
    Full-text · Article · Dec 2015 · New Phytologist
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    • "The mechanistic basis of scion dwarfing has been well explored in apple (Kamboj et al., 1999a, 1999b; Bulley et al., 2005; Pilcher et al., 2008; Van Hooijdonk et al., 2011; Li et al., 2012; Vattiprolu, 2012), sweet cherry (Lang et al., 2002; Olmstead et al., 2006; Hajagos and Végvári, 2013), beech (Weibel et al., 2003; Solari and DeJong, 2006; Weibel, 2008; Tombesi et al., 2010) and kiwifruit (Clearwater et al., 2004, 2006, 2007). Several genes implicated with the dwarfing effect have been tagged and isolated (Prassinos et al., 2009; Zhu et al., 2008), although not so far in pear. Meanwhile, the causal signals of the mechanisms for scion control by rootstocks are still uncertain and may differ between crop species (Gregory et al., 2013). "
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    ABSTRACT: Dwarfing rootstocks, such as that of the Chinese pear variety ‘Zhongai 1’, are an important resource in modern fruit production. An RNA-Seq analysis of ‘Zhongai 1’ and its progenitor non-dwarfing variety ‘Jinxiang’ revealed a set of 234 genes which were differentially transcribed in the two varieties. Among the differentially transcribed gene set were some potential candidates for the dwarf trait: one encoded a gibberellin 3-beta-dioxygenase, four encoded auxin-associated proteins, one encoded an LRR receptor-like serine/threonine-protein kinase, four encoded cytochrome P450s, two encoded enzymes involved in abscisic acid synthesis, three were ethylene-responsive transcription factors, six were moisture status related proteins, two were NAC and four WRKY transcription factors. The assessment of transcript abundance derived by the RNA-Seq analysis was validated using quantitative real time PCR for ten of the differentially transcribed genes. The transcript levels of these genes in other dwarf and non-dwarf varieties were also analyzed by the qPCR, but no completely consistent regularity was found. The concentration of some phytohormones (GA3, IAA and ABA) were also determined, the results accorded with the transcript levels of some related genes in the some varieties, but did not in all the survey varieties.
    Full-text · Article · Oct 2015
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    • "Since gai is a semi-dominant and gain-of-function mutation [8], integration of gai into WT results in a semi-dwarf phenotype, and this has contributed to the Green Revolution [29]. The stature of several crops, including rice [13], Chrysanthemum[30], tobacco [27], and apple [28], has been reduced by transformation with ΔDELLA-GAI (gai), as is the case for the Arabidopsis gai-1 allele. In all cases, ΔDELLA-GAI (gai) was expressed under the control of CaMV 35S (Cauliflower Mosaic Virus promoter 35S). "
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    ABSTRACT: The Gibberellic Acid (GA) signal is governed by the GAI (Gibberellic Acid Insensitive) repressor, which is characterized by a highly conserved N-terminal DELLA domain. Deletion of the DELLA domain results in constitutive suppression of GA signaling. As the GAI transcript is transportable in phloem elements, a Delta-DELLA GAI (gai) transgenic stock plant can reduce the stature of a scion through transport of gai mRNA from the stock. However, little is known about the characteristics of a scion on a gai stock. Arabidopsis Delta-DELLA GAI (gai) was fused with a T7 epitope tag and expressed under the control of a companion cell-specific expression promoter, Commelina yellow mottle virus promoter (CoYMVp), to enhance transport in the phloem. The CoYMVp:Atgai-T7 (CgT) transgenic Nicotiana benthamiana exhibited a dwarf phenotype and lower sensitivity to GA enhancement of shoot stature. A wild-type (WT) scion on a CgT stock contained both Atgai-T7 mRNA and the translated product. Microarray analysis to clarify the effect of the CgT stock on the gene expression pattern in the scion clearly revealed that the WT scions on CgT stocks had fewer genes whose expression was altered in response to GA treatment. An apple rootstock variety, Malus prunifolia, integrating CoYMVp:Atgai moderately reduced the tree height of the apple cultivar scion. Our results demonstrate that Atgai mRNA can move from companion cells to sieve tubes and that the translated product remains at the sites to which it is transported, resulting in attenuation of GA responses by reducing the expression of many genes. The induction of semi-dwarfism in an apple cultivar on root stock harbouring Atgai suggests that long-distance transport of mRNA from grafts would be applicable to horticulture crops.
    Full-text · Article · Oct 2013 · BMC Plant Biology
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