Functional characterisation of a gene family encoding circadian regulated glycine-rich RNA-binding proteins in Arabidopsis thaliana

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The overall goal of this project is a functional characterisation of the clock-controlled RNA-binding proteins AtGRP7 (Arabidopsis thaliana glycine-rich RNA-binding protein) and AtGRP8. AtGRP7 is part of a negative feedback loop through which it regulates oscillations of its own transcript as well as of the atgrp8 transcript. We suggest that the AtGRP7 feedback loop is involved in transmitting timing signals generated by a central circadian clock to clock-controlled processes within the cell. To define the function of this feedback loop we propose to identify target transcripts of AtGRP7. Since such transcripts are expected to show an altered expression in transgenic plants constitutively overexpressing AtGRP7 (AtGRP7-ox), transcript profiles will be compared between wild type plants and AtGRP7-ox plants employing DNA microarrays. Moreover, transgenic plants with reduced expression of Atgrp7 and Atgrp8 will be generated to investigate the phenotypical consequences of reduced expression for morphology and physiology of the plants. To obtain a comprehensive overview about the conditions under which AtGRP7 and AtGRP8 may preferentially be active, their expression pattern during development and in response to external stimuli and stress factors will be investigated in detail in consideration of the underlying clock regulation.