Poster: Photomorphogenesis

Abs # 502: Light dependent degradation of Phytochrome A is restricted in the N-terminal region of Phytochrome A

Presenter:	Lim, Jong-Min , ljm114@hanmail.net
Authors	Lim, Jong-Min  (A)   Lee, Youn-Hyung  (A)   Jeon, Jong-Seong  (A)   Vierstra, Richard  (B)   Bhoo, Seong Hee  (A)   Hahn, Tae-Ryong  (A)
Affiliations:	(A): Kyung Hee University (B): University of Wisconsin-Madison

The ubiquitin/26S proteasome pathway is a well known proteolysis pathway of many signaling proteins. Recent studies have shown that this pathway is also connected to the degradation of some proteins in higher plants. The well known photoreceptor phytochrome A (PhyA) from its inactive Pr form to its biologically active Pfr form initiates the rapid degradation of this protein. The ubiquitin/26S proteasome pathway has a main role for red light specific Phytochrome A degradation. Previous kinetic and biological studies implicated that multiple domains within the chromoprotein are involved in the ubiquitin binding and its specific degradation. To further resolve the essential domains, a series of chimeric photoreceptors were constructed and over-expressed in transgenic plant and analyzed the ubiquitination and degradation. N-terminal ubiquitination was surprising result because it was contradictory to the previous report that the ubiquitination was on the C-terminal domain. Several N-terminal domains were exchanged and swapped between potato phytochrome A and B. Data analysis showed that about 60 amino acids region right after chromophore binding site of phytochrome A was important for the Pfr specific degradation of phytochrome A. There may be ubiquitination sites in this degradation region where two lysines are highly conserved.