The ABA- and Stress-Induced Expression of the ArabidopsisthalianaAt4g0180 Gene Is Determined by the Cis-Elements Responsible for Binding the ABA-Dependent Trans-Factors

In silico analysis of the promoter region of the At4g01870 gene of Arabidopsis thaliana (L.) Heynh. showed the presence of ABRE, W-box, RAV1-A, MYB, and LFY cis-elements in the sequence. These regulatory motifs bind the transcription factors involved in responses to abscisic acid (ABA) and stresses. Stable transgenic plants carrying the β-glucuronidase gene under the control of the 5'-deletion fragments of the At4g01870 promoter were obtained. According to the results of histochemical staining of transformants, gene expression was induced by abiotic stress and was most significant in the conductive tissues of the root, leaves, and sepals as well as in flowers. The study of At4g01870 gene expression by RT-PCR confirmed that the gene transcript content increased after the exposure of plants to a solution of NaCl or at 37°C and after ABA treatment; however, hypothermia almost unchanged the level of accumulation of the transcripts. Along with ABA, expression of the At4g01870 gene was induced by indolylacetic and salicylic acids and ethylene precursor 1-aminocyclopropane-1-carboxylic acid; it was hardly regulated by methyl jasmonate and inhibited by cytokinin. The TolB-like protein, encoded by the At4g01870 gene, functions as a type of platform, based on which protein complexes are assembled. Given the previously identified ABA-binding properties of the protein At4g01870 and the presence of the ABA-dependent cis-elements in the promoter of its coding gene, it can be assumed that the protein encoded by the At4g01870 gene allows to control the hormonal signals in the cell, providing a structural platform for the interaction of specific effector proteins, trans-factors and ion channels.