Positive and Negative Regulatory Regions Control the Spatial Distribution of Polygalacturonase Transcription in Tomato Fruit Pericarp

Department of Plant Biology, University of California, Berkeley 94720.
The Plant Cell (Impact Factor: 9.34). 10/1993; 5(9):1049-62. DOI: 10.1105/tpc.5.9.1049
Source: PubMed


The tomato fruit consists of a thick, fleshy pericarp composed predominantly of highly vacuolated parenchymatous cells, which surrounds the seeds. During ripening, the activation of gene expression results in dramatic biochemical and physiological changes in the pericarp. The polygalacturonase (PG) gene, unlike many fruit ripening-induced genes, is not activated by the increase in ethylene hormone concentration associated with the onset of ripening. To investigate ethylene concentration-independent gene transcription in ripe tomato fruit, we analyzed the expression of chimeric PG promoter-beta-glucuronidase (GUS) reporter gene fusions in transgenic tomato plants. We determined that a 1.4-kb PG promoter directs ripening-regulated transcription in outer pericarp but not in inner pericarp cells, with a sharp boundary of PG promoter activity located midway through the pericarp. Promoter deletion analysis indicated that a minimum of three promoter regions influence the spatial regulation of PG transcription. A positive regulatory region from -231 to -134 promotes gene transcription in the outer pericarp of ripe fruit. A second positive regulatory region from -806 to -443 extends gene activity to the inner pericarp. However, a negative regulatory region from -1411 to -1150 inhibits gene transcription in the inner pericarp. DNase I footprint analysis showed that nuclear proteins in unripe and ripe fruit interact with DNA sequences within each of these three regulatory regions. Thus, temporal and spatial control of PG transcription is mediated by the interaction of negative and positive regulatory promoter elements, resulting in gene activity in the outer pericarp but not the inner pericarp of ripe tomato fruit. The expression pattern of PG suggests that, although they are morphologically similar, there is a fundamental difference between the parenchymatous cells within the inner and outer pericarp.

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Available from: Jill Deikman, Mar 25, 2015
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    • "SlPG expression is attributed to the distal 3.4 kb of the 4.8 kb promoter sequence, which contains a 400 bp imperfect reverse repeat that shares high sequence similarity to the promoter sequence of the ripening-related E8 [9]. Additionally, a positive cis-element (−806–443), responsible for expression in both inner and outer pericarp, and a negative cis-element (−1411–1150), restricting expression to the outer pericarp, were identified in the SlPG promoter [10]. Thus, SlPG is thought to have ripening-specific expression in tomato fruits. "
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    • "As part of the molecular characterization of ripening, the identification of fruit-specific promoters has not only contributed to the description of this process, but has provided important tools for fruit biotechnology (Estornell et al., 2009; Fernandez et al., 2009) In general, ripening promoters reproduce the expression pattern of the corresponding gene by providing the correct or tissue specificity stage (Beaudoin and Rothstein, 1997; Deikman et al., 1998; Montgomery et al., 1993; Nicholass et al., 1995). All the fruit ripening promoters described to date provide either a uniform expression or a gradient across the tissue, with no preference for individual cells in a given tissue. "
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    • "The GhPRP3 and GhCHS1 promoters were analysed computationally for the presence of previously characterised transcription factor binding sites and shared novel motifs with the MEME (Bailey and Elkan 1994) and MatInspector (Quandt et al. 1995) programs. Since the present study identified only two suitable promoters, several promoters that drive similar expression patterns in equivalent tissues of other species (AGL5 (Liu et al. 2008), AT2G40250 (Xiao et al. 2010), PG (Montgomery et al. 1993), PPC2 (Fernandez et al. 2009) and CRC (Fernandez et al. 2009; Lee et al. 2005)) were also included in the bioinformatic analysis. Many previously characterised transcription factor binding sites were present in both the GhPRP3 and GhCHS1 promoters with all but one of these identified in at least one of the other five promoters used in this analysis (Table S1 in the Electronic Supplementary Material (ESM)). "
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