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Doctoral thesis, 2011

Regulation of organ development by auxin and the SHI/STY-family of transcriptional regulators

Ståldal, Veronika


Transcription factors, proteins regulating the transcription of target genes, and plant hormones play important roles in the regulation of plant development. The plant hormone auxin has been assigned functions in many developmental processes and its differential distribution between cells, created mainly by local auxin biosynthesis and polar auxin transport, results in auxin maxima and gradients, which appear to be important for its role in developmental regulation. The work in this thesis reveals that members of the Arabidopsis thaliana SHI/STY protein family, which redundantly regulates the development of lateral organs, act as DNA binding transcriptional activators. The SHI/STY member STY1, expressed at specific sites in developing primordia and organs, binds to the promoter of the YUC4 auxin biosynthesis gene. Our data suggest that the control of local auxin biosynthesis, through transcriptional activation of e.g. YUC4, is important for SHI/STY regulated development of lateral organs. We could show that local auxin application restores SHI/STY mutant style defects. Furthermore, using a polar auxin transport inhibitor, auxin was found to act independently of the style-promoting factors CRC, LUG, SEU, SPT and STY1 in style development, suggesting that auxin may act downstream or in parallel with these genes, but not in apical-basal patterning of the gynoecium. Additional STY1 downstream targets have been identified and include genes encoding transcription factors, another auxin biosynthesis enzyme, and enzymes involved in cell expansion. Functional studies on some of these genes reveal roles in stamen and leaf development as well as in flowering time regulation. The upstream regulation of SHI/STY genes has also been studied and a conserved GCC-box-like promoter element has been shown to be important for the transcriptional regulation of SHI/STY genes, providing a possible mechanism for the co-regulation of the SHI/STY protein accumulation.


auxins; arabidopsis thaliana; gynoecium; leaves; stamens; biosynthesis; genes; transcription; transcription factors

Published in

Acta Universitatis Agriculturae Sueciae
2011, number: 2011:14
ISBN: 978-91-576-7549-1
Publisher: Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences

Authors' information

Ståldal, Veronika (Ståldal, Veronika)
Swedish University of Agricultural Sciences, Department of Plant Biology

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