Untersuchungen zur Funktion von Nuclear Bodies in Pflanzen durch lokal-optische Spektromikroskopie

• Applicants: Professor Dr. Andreas Hiltbrunner; Privatdozent Dr. Frank Schleifenbaum
• Subject Area: Plant Biochemistry and Biophysics
• Term: from 2011 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 200965010

• Final Report Year: 2015

Final Report Abstract

Phytochromes are red/far-red photoreceptors in plants essential for light-regulated growth and development. Photomorphogenesis is suppressed by the action of the CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1)/SUPPRESSOR OF phyA-105 (SPA) complex, which targets positive regulators of photomorphogenic growth for degradation by the proteasome. Light-activated phytochromes inhibit the COP1/SPA complex, thereby promoting the accumulation of positive regulators of photomorphogenesis. Yet, the mechanism by which phytochromes inactivate COP1/SPA has been unknown. In this project, we have shown that light-activated phytochrome A (PHYA) and phytochrome B (PHYB) interact with SPA1 and other SPA proteins and inhibit their binding to COP1. Phytochromes and SPAs colocalise in nuclear bodies and Förster resonance energy transfer-fluorescence lifetime imaging microscopy (FRET-FLIM) analyses show that SPAs and phytochromes interact in these subnuclear structures. Moreover, PHYA and PHYB disrupt the interaction between COP1 and SPAs in living plants in response to irradiation with light, resulting in reorganisation of the COP1/SPA complex and initiation of photomorphogenic development. These data provide a molecular mechanism for the inactivation of the COP1/ SPA complex by PHYA- and PHYB photoreceptors.

Publications

• (2014). Shedding (far-red) light on phytochrome mechanisms and responses in land plants. Plant Sci. 217-218: 36–46
  Possart, A., Fleck, C., and Hiltbrunner, A.
  (See online at https://doi.org/10.1016/j.plantsci.2013.11.013)
• (2015). Light- Activated Phytochrome A and B Interact with members of the SPA family to promote photomorphogenesis in Arabidopsis by reorganizing the COP1/SPA complex. Plant Cell 27: 189–201
  Sheerin, D.J., Menon, C., Zur Oven-Krockhaus, S., Enderle, B., Zhu, L., Johnen, P., Schleifenbaum, F., Stierhof, Y.-D., Huq, E., and Hiltbrunner, A
  (See online at https://doi.org/10.1105/tpc.114.134775)