Functional dissection of a napin gene promoter: identification of promoter elements required for embryo and endosperm-specific transcription

Abstract

The promoter region (-309 to +44) of the Brassica napus storage protein gene napA was studied in transgenic tobacco by successive 5' as well as internal deletions fused to the reporter gene GUS (beta-glucuronidase). The expression in the two main tissues of the seed, the endosperm and the embryo, was shown to be differentially regulated. This tissue-specific regulation within the seed was found to affect the developmental expression during seed development. The region between -309 to -152, which has a large effect on quantitative expression, was shown to harbour four elements regulating embryo and one regulating endosperm expression. This region also displayed enhancer activity. Deletion of eight bp from position -152 to position -144 totally abolished the activity of the napA promoter. This deletion disrupted a cis element with similarity to an ABA-responsive element (ABRE) overlapping with an E-box, demonstrating its crucial importance for quantitative expression. An internal deletion of the region -133 to -120, resulted in increased activity in both leaves and endosperm and a decreased activity in the embryo. Within this region, a cis element similar to the (CA)n element, found in other storage protein promoters, was identified. This suggest that the (CA)n element is important for conferring seed specificity by serving both as an activator and a repressor element.

Enhanced Seed Oil Production in Canola by Conditional Expression of Brassica napus LEAFY COTYLEDON1 and LEC1-LIKE in Developing Seeds

“…studies revealed that wild-type and the mutant napA promoters, including 21101 (D1), 2309 (D2), 2211 (D7), and 2152 (D8), showed a similar expression pattern at different developmental stages of embryogenesis in the transgenic tobacco plants, although the expression level of the mutant promoters varied significantly. The promoter reporter constructs had barely detectable expression 5 to 10 d after pollination (DAP; globule to heart stages), followed by significant expression at 10 to 15 DAP (heart to torpedo stages), and reached the highest expression level 30 DAP (Stålberg et al, 1993;Ellerströ m et al, 1996). Consistent with these results, expression of D7:BnL1L (see below) in the transgenic Arabidopsis embryos was detectable around 7 to 10 DAP and had a higher expression level at 13 DAP (Supplemental Fig.…”

“…Previous studies on the napA promoter indicated that the sequences between 2152 and +44 are essential for the seed-specific expression pattern in transgenic tobacco plants, and several ciselements upstream from 2152 were found to act as positive or negative regulatory motifs (Stålberg et al, 1993;Ellerströ m et al, 1996). We made similar napA promoter GUS reporter constructs that were stably transformed into Arabidopsis plants.…”

Evolutionary fate of rhizome-specific genes in a non-rhizomatous Sorghum genotype

“…Evolutionary fate of rhizome-specific genes transcription (Ellerstrom et al, 1996), also showed lower frequencies in the promoter regions of S. bicolor and O. sativa than S. propinquum. Another possibility for partial loss of subfunctions of the RT-enriched genes in domesticated genotypes would be that an alternative splice form with rhizomespecificity is lost but the other form(s) still remain due to their importance in other organs.…”

“…Five additional cis-acting regulatory elements, such as CRT/DRE motif (Xue, 2003), (CA) n element in storage protein genes (Ellerstrom et al, 1996), TATA box (Grace et al, 2004), the CCA1-binding element related to regulation by phytochrome (Wang et al, 1997), and pyrimidine box required for gibberellic acid (GA) induction (Cercos et al, 1999), were also more abundant in S. propinquum than either S. bicolor or O. sativa alleles (Table 3).…”

Two Acyltransferases Contribute Differently to Linolenic Acid Levels in Seed Oil

“…Napin is expressed specifically in the whole embryo and in fully developed seeds, and no apparent difference is seen in its expression within the embryo (Ellerström et al, 1996). However, there are differences during seed development.…”