Two cis-acting regulatory elements are involved in the sucrose-inducible expression of the sporamin gene promoter from sweet potato in transgenic tobacco

Abstract

In this study, we generated transgenic tobacco plants that express the beta-glucuronidase (GUS) gene under the control of the 305-bp 5'-upstream region of a gene coding for sporamin A of sweet potato. Expression of GUS in excised tobacco leaves was induced by sucrose, mimicking the sugar-inducible expression of the endogenous sporamin genes in sweet potato. Deletion of the sequences extending from position -305 (relative to the transcription start site) to -283 and from -146 to -87 resulted in an approximately 40-fold enhancement in GUS reporter expression. Furthermore, the sequence from -282 to -165 conferred sucrose-inducibility on the -89 core promoter of the Cauliflower Mosaic Virus 35S RNA gene. Analysis of internal deletions, linker scanning and the introduction of base substitutions in the sequence between positions -282 and -165 indicated that sucrose-responsiveness conferred by this region was dependent on the presence of two cis-acting elements, termed CMSREs (carbohydrate metabolite signal responsive elements) 1 and 2, which are separated by a spacer. A sequence similar or identical to the core of CMSRE-1 (TGGACGG) is also present in the promoters of several other sugar-inducible genes, and sequences encopassing the TGGACGG-related motifs from two of these could functionally replace the CMSRE-1 in the truncated sporamin A promoter. These results suggest that the TGGACGG element plays an important role in the sucrose-inducible expression of a group of plant genes.

Analysis of a Sugar Response Mutant of Arabidopsis Identified a Novel B3 Domain Protein That Functions as an Active Transcriptional Repressor

“…hsi2 Mutant Exhibits High-Level Expression of the Spo min Promoter A 210-bp ''minimal'' promoter derived from a gene for sweet potato sporamin A1 (Spo min ; Morikami et al, 2005) directed sugar-and ABA-inducible expression of the LUC and GUS reporter gene in leaves of Arabidopsis. Mutants displaying altered patterns of Sucinducible expression of LUC were isolated from the transgenic line sGsL, which carries a single copy of T-DNA containing the Spo min TGUS-Spo min TLUC dual reporter genes (Fig.…”

“…Dissection of the promoter region of gSpoA1 using a b-glucuronidase (GUS) reporter in tobacco (Nicotiana tabacum) yielded a 210-bp sugar-inducible ''minimal'' promoter (Spo min ; Morikami et al, 2005). Expression of sporamin genes is also inducible by ABA (Ohto et al, 1992), and Spo min directed sugar-and ABA-inducible expression of GUS and luciferase (LUC) reporters in Arabidopsis.…”

Transcription factors for sugar-inducible genes

“…Promoter analysis of sporamin A1 gene in tobacco using bglucuronidase (GUS) reporter yielded a 210-bp sugarinducible "minimal" promoter (Spo min ; Morikami et al 2005). Expression of sporamin genes is also inducible by ABA (Ohto et al 1992) :LUC dual reporter genes was characterized for the sugar-and ABAinducible expression of GUS and LUC activities.…”

“…Morikami et al, manuscript in preparation). Several regions of Spo promoter can function negatively on expression and even the short Spo min and b-Amy min promoters contain at least two separate positive cis-elements required for the maximum level of sugar-inducible expression (Maeo et al 2001b;Morikami et al 2005). Overexpression or mutation in ASML1/WRI1, ASML2 and HSI2 affects expression of Spo min and these transcription factors either trans-activate or -repress transient expression of Spo min in protoplasts (Figure 4; Tsukagoshi et al 2005;Masaki et al 2005a, b).…”

High-level expression of sucrose inducible sweet potato sporamin gene promoter: &#x3b2;-glucuronidase fusion gene in transgenic <i>Nicotiana plumbaginifolia</i>

“…Although sporamin gene expression is normally specific to tuberous roots (Maeshima et al 1985), expression has also been induced in sweet potato leaves and petioles by sucrose, glucose and fructose treatment (Hattori et al 1990. Morikami et al (2005) …”