FG 804: Retrograde Signaling in Plants - Teilprojekt 2: Dissection of the tetrapyrrole-mediated signaling pathway: Identification of componenets involved in signal transduction and of target genes

Biosynthesis, accumulation and degradation of tetrapyrroles are conceivably associated with chloroplast development, photomorphogenesis and plastid-to-nucleus signaling. Experimental data provide evidence that bi-directional exchange of information between DNA-containing organelles bases on the operation of multiple signaling pathways and that the tetrapyrrole biosynthetic pathway, mainly its Mg branch for chlorophyll biosynthesis, mediates retrograde signaling to adjust nuclear transcriptional activities in response to plastid enzymatic and regulatory activities. The general objective of the proposal to dissect functionally the signaling pathway, which is derived from the tetrapyrrole biosynthetic pathway, will be approached by the identification (i) of the target genes of tetrapyrrole-mediated signaling and (ii) of additinal componenets at the site of signal origin in plastids. The first aim will be achieved with time-resolved analysis of transcript profiles of Arabidopsis transformants with temporarily induced deregulation of the Mg porphyrin-synthesizing pathway. Secondly, novel signaling components are aimed to be detected in the multi-enzymatic complex consisting of enzymes of the Mg branch and to explore their role for the generation and transductin of the tetrapyrrole pathway-released signal.