Poster: Temperature responses

Abs # 130: The role of misfolded proteins (rubisco from the diatom Phaeodactylum tricornutum) in the induction of heat shock proteins in tobacco (Nicotiana tabacum).

Presenter:	Pike, Carl S., carl.pike@fandm.edu
Authors	Pike, Carl S. (A)   Filone, Claire Marie  (A)   Goh, Jo W. (A)   Walsh, Megan C. (A)   Whitney, Spencer M. (B)   Andrews, John  (B)
Affiliations:	(A): Franklin and Marshall College (B): Australian National University

After exposure to stressful conditions, cells increase expression of heat shock proteins, a set of proteins that have been implicated in the protection of protein structure and function. A common consequence of the stresses that induce the heat shock response may be that they cause unfolding of proteins. Therefore, heat shock protein expression may be induced by the presence of misfolded proteins. We investigated the role of misfolded proteins in the induction of heat shock proteins in Nicotiana tabacum L. var. Petit Havana transformed with the rubisco large and small subunit genes from the diatom Phaeodactylum tricornutum. The transgenic tobacco plants expressed P. tricornutum rubisco subunits that are misfolded and do not assemble into the rubisco holoenzyme. Content of heat shock proteins was assessed by immunoblotting of extracts (supernatant and pellet fractions) from mature leaf tissue. The content of HSP 60 was much greater in transgenic plants (and in heat-shocked plants) than in untransformed control plants; immunoreactivity was confined to the supernatant fraction. An increase in HSP 93 was also observed in transgenic and heat-shocked plants relative to controls. Although heat shock substantially increased the level of small HSPs, these proteins were not detected in transgenic plants. There were no noticeable differences in the content of cytoplasmic HSP 70 and of stromal HSP 78 between transgenic and control plants. These results provide support for the hypothesis that the presence of misfolded proteins induces the production of heat shock proteins, but the response is restricted to certain classes of heat shock proteins. Supported by institutional and Howard Hughes Medical Institute funds from Franklin and Marshall College.