Functional analyses of cis-acting elements of sporamin gene promoter from sweet potato and investigation of the polymorphisms between sporamin gene members
Date Issued
2005
Date
2005
Author(s)
Chang, Hsiao-Chi
DOI
zh-TW
Abstract
Sporamin is a storage protein of sweet potato tuber, and the expression of sporamin gene in leaves is wound-inducible. In order to define the wound-response cis-acting elements of the sporamin promoter, the genomic walking method was used to clone upstream promoter regions. Three segments of promoter region of this gene family were obtained. Although the sequences of these promoters are various, they all contain almost the same cis-acting elements, such as W-box and GCC-box. Therefore, the expression pattern of each gene member may be quite similar. Our previous data demonstrated that a sporamin promoter : SP1 (pSPOA) is wounding-induced in the transgenic tobacco by promoter-GUS fusion assay. The GUS staining results indicate that the sequences containing the NOS-like element confer the most wound-induced activity, the SP8a and G-box may contribute to enhance the effect of NOS-like element. So we use the synthetic promoter method to identify each cis-acting element. Constructions with one, two and four copies of each element were tested for its wounding-induced activity by promoter-GUS fusion assays. We also tested the constructs with mixed motifs in transgenic Arabidopsis. The GUS staining and GUS quantitative results showed that both the NOS-like element and the SP8a motif contribute to the GUS expression under mechanical wounding in transgenic Arabidopsis. The NOS-like element and SP8a motif indeed confer wounding-induced activity when working alone, but the expression level of the reporter gene is higher when the number of motif increased. Although the induced level of GUS proteins was different between these constructs, the expression patterns were quite similar. The induced GUS proteins were expressed in wounded leaf, root, stem, and unwounded leaves. So the wounding response might be a systemic effect.
We also constructed a cDNA library of sweet potato tuberous root to clone more sporamin genes, because we intend to investigate the polymorphisms among these genes. Twenty sporamin genes were cloned, 19 of these genes belong to the sporamin A and only one gene belong to the sporamin B. The homology between these two groups is 80％, and the homology within each group is about 90％. We also divide the sporamin A into two sub-family, and the homology within each sub-family is 95％. The sequence polymorphisms are taking place almost in the 5’, and 3’-UTR, these findings are resemble with the theory proposed by Hattori in 1989. We found that the active domain within amino acid sequences of these sporamin genes were identical, so the activities of these proteins might be the same. And the evolution prediction of this gene family tends to purifying evolution pathway.
Subjects
胰蛋白酶
抑制因子
受傷誘導
基因家族
sporamin
wounding
trypsin inhibitor
Type
other
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