Abstract
The Maize Wip1 gene encodes a wound-induced Bowman-Birk inhibitor (BBI) protein which is a type of serine protease inhibitor, and its expression is induced by wounding or infection, conferring resistance against pathogens and pests. In this study, the maize Wip1 promoter was isolated and its function was analyzed. Different truncated Wip1 promoters were fused upstream of the GUS reporter gene and transformed into Arabidopsis, tobacco and rice plants. We found that (1) several truncated maize Wip1 promoters led to strong GUS activities in both transgenic Arabidopsis and tobacco leaves, whereas low GUS activity was detected in transgenic rice leaves; (2) the Wip1 promoter was not wound-induced in transgenic tobacco leaves, but was induced by wounding in transgenic rice leaves; (3) the truncated Wip1 promoter had different activity in different organs of transgenic tobacco plants; (4) the transgenic plant leaves containing different truncated Wip1 promoters had low GUS transcripts, even though high GUS protein level and GUS activities were observed; (5) there was one transcription start site of Wip1 gene in maize and two transcription start sites of GUS in Wip1::GUS transgenic lines; (6) the adjacent 35S promoter which is present in the transformation vectors enhanced the activity of the truncated Wip1 promoters in transgenic tobacco leaves, but did not influence the disability of truncated Wip1231 promoter to respond to wounding signals. We speculate that an ACAAAA hexamer, several CAA trimers and several elements similar to ACAATTAC octamer in the 5′-untranslated region might contribute to the strong GUS activity in Wip1231 transgenic lines, meanwhile, compared to the 5′-untranslated region from Wip1231 transgenic lines, the additional upstream open reading frames (uORFs) in the 5′-untranslated region from Wip1737 transgenic lines might contribute to the lower level of GUS transcript and GUS activity.
Highlights
It is necessary to use different promoters when multiple genes are cloned in tandem in transgenic plants because multiple copies of a single promoter could lead to the silencing of the transgenes.Promoters may be classified as constitutive, tissue-specific, or inducible based on their expression patterns
Six W-boxes and three GCC-boxes were found in the Wip1 promoter
We investigated whether the Wip1 promoter is wound-induced in transgenic tobacco plant leaves that were wounded with three different kinds of wounding methods, respectively
Summary
It is necessary to use different promoters when multiple genes are cloned in tandem in transgenic plants because multiple copies of a single promoter could lead to the silencing of the transgenes. Promoters may be classified as constitutive, tissue-specific, or inducible based on their expression patterns. Several other strong promoters have been isolated and identified from plants or viruses [4,5,6]. Many promoters have been isolated and tested, only a few have been successfully used in agricultural biotechnology. The constitutive expression of certain genes might be harmful to their host plants, affecting plant growth and development; inducible or tissue-specific promoters would be more useful than constitutive promoters in these cases
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