Functional analysis of the N-terminal domain of SPA1
Stefan Dieterle
Résumé:
Plants adapt to their light environment by regulating several key developmental processes like seedling de-etiolation and the transition from vegetative to reproductive growth. Arabidopsis thaliana is a facultative long day flowering plant. It has evolved mechanisms to time its flowering according to seasonal and environmental cues. There are several signaling pathways for flowering time control that can be distinguished by the environmental or developmental cues they transduce. One important pathway, the photoperiodic pathway, allows plants to time flowering according to seasonal changes. The current understanding is that plants measure day length through the integration of internal signals from the circadian clock and external light cues. The central integrator of these signals CONSTANS (CO) is controlled at the transcriptional level by the plant circadian clock and at the post-translational level by light through protein degradation in darkness. CO is targeted for degradation in darkness by the CONSTITUTIVE PHOTOMORPHOGENIC 1/SUPRESSOR OF PHYA-105 (COP1/SPA) E3 ubiquitin ligase complex. SPA1 is a member of a small gene family comprising four members. Of the four SPAs, SPA1 has the most important function in flowering time control. SPA1, like COP1, contains a WD repeat domain and a coiled coil domain. Unlike COP1 it contains a kinase-like domain. Complementation assays have shown that the N-terminal kinase-like domain of SPA1 is essential for its function in flowering time control but not for seedling de-etiolation. To further investigate the function of the N-terminal domain of SPA1, single amino acid exchanges in residues conserved in kinases were performed and used for complementation assays. These assays have revealed that some of these amino-acids are essential for SPA1 function in flowering time control and implicated in seedling de-etiolation specifically in red (R) light. The data presented here indicate that either the putative kinase function or the kinase-like structure of SPA1 is essential for its function in photoperiodic flowering time control and the physical interaction of SPA1 with CO and COP1. Furthermore the SPA1 N-terminal domain is essential for seedling photomorphogenesis specifically in R light suggesting a function of that domain in a phyBspecific signaling pathway.
Revue:
Thèse de l'Université de Berlin
Lien: