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Getachew Liku Aregawi

Getachew Liku Aregawi

Haramaya University, Ethiopia

Title: Analysis of the ABP1 promoter in Arabidopsis expressing promoter fragments coupled to the GUS indicator gene

Biography

Biography: Getachew Liku Aregawi

Abstract

The role of auxin at molecular level in exerting rapid and specific effects on gene regulation has been reported by a number of studies. However, the mechanism of auxin perception and the identity of receptors are not fully elucidated. Transport Inhibitor Response 1 (TIR1) has been clearly identified as a receptor of auxin in the nucleus. In a sandwich complex, TIR1 and IAA proteins bind auxin and this leads to proteosome mediated degradation of IAA proteins as negative transcriptional co-regulators. TIR1 has no role for very rapid cellular responses of auxin application at plasma membrane. Auxin-Binding-Protein 1 (ABP1) is a good candidate for this alternative auxin signaling pathway which is implicated in non transcriptional auxin signaling. ABP1 itself is expressed as auxin responsive gene mediated by TIR1. In this project the expression of ABP1 and thus, its role in auxin signaling has been investigated using a promoter GUS approach. Initially, two promoter fragments without exon-intron sequences coupled to the GUS gene were transformed into Arabidopsis and analyzed; these plants did not express GUS activities. Two promoter regions, one with exon and intron sequences downstream of the start codon (ABP1 (exon-intron)) and one without downstream sequences were additionally analyzed using the GUS activities in response to auxins and light. The GUS activity was strong in the seedlings expressing promoter regions with exon-intron sequences while there were low activities without exon-intron sequences observed after exogenous auxin or light treatment. The activity of GUS expressed by extended promoter with exon-intron and the positive control DR5-GUS increased with time and the concentration of exogenous auxin treatment. The extended promoter (ABP1 (exon-intron)) also showed higher GUS activities in response to red light and blue light while the promoter without exon-intron sequences and DR5 seedlings showed no GUS activities at all light conditions except low activity of GUS in the shoot meristem of DR5-GUS seedlings in response to red light. Generally, expression of GUS was observed around young leaves and root tips in response to auxin and light treatment.