Trends in Plant Science
Volume 4, Issue 6, 1 June 1999, Pages 210-214
Journal home page for Trends in Plant Science

Review
Regulatory mechanism of plant gene transcription by GT-elements and GT-factors

https://doi.org/10.1016/S1360-1385(99)01418-1Get rights and content

Abstract

GT-elements are regulatory DNA sequences ususally found in tandem repeats in the promoter region of many different plant genes. Depending on promoter structure, GT-elements can have a positive or a negative transcription function. The cognate GT-element binding factors contain one or two trihelix DNA binding motifs, which have so far been identified in plant transcription factors only. GT-factors are ubiquitously expressed; in Arabidopsis they belong to a small family of transcription factors. The functioning of plant GT-elements and GT-factors shows complex regulatory features of plant gene transcription.

Section snippets

A highly degenerated cis-element

GT-elements were first identified in the pea ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit gene (RBCS-3A) promoter as Box II (5′GTGTGGTTAATATG)4. The cognate DNA-binding activity, named GT-1, also binds to several other related but divergent sequences found in this promoter5 (Fig. 1). The deduced consensus core sequence is 5′-G-Pu-(T/A)-A-A-(T/A). GT-elements have been found in the promoter region of many other genes encoding diverse functions5, 6, 7, 8, 9, 10, 11, 12,

A necessary but not sufficient element for light-activation

Deletion or point mutation of GT-elements in a few light-responsive genes does not affect light-induced transcription from these promoters5. This lack of effect might be at least partially caused by the presence of redundant GT-elements in these promoters. Gain-of-function experiments in transgenic tobacco showed that a tetramer of the GT-1 site (Box II) can confer light responsiveness to an otherwise light-irresponsive CaMV 35S-90 promoter (cauliflower mosaic virus 35S promoter region from

Trihelix DNA-binding GT-factors

There is no differential GT-element (Box II) binding activity observed in nuclear extracts from green or etiolated leaves5. However, tobacco root cell extracts contain a different Box II binding activity with a distinct sequence specificity and form a DNA–protein complex of higher electrophoretic mobility35. Moreover, the GT-element (Box II) binding activity from det mutant leaf nuclear extracts has a higher electrophoretic mobility than the one from normal plant leaves36, suggesting possible

Acknowledgements

My thanks to Dr F. Guerineau for critical reading of the manuscript and to L'Association Biopôle Végétal de Picardie, France, for support.

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