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| Professor Ortiz meeting with one of his cutthroat advisees from the Honors College. |
In our view, one of the great challenges of current research in plant molecular biology is to elucidate the molecular basis of the interaction between the nucleocytoplasmic compartment and the chloroplast during chloroplast development. We are currently studying the molecular basis of the temperature-induced bleaching phenomenon in the unicellular alga Euglena gracilis to gain insight into the rules that govern chloroplast development and maintenance in plant cells.
This system is of particular interest to us because photoheterotrophic cultures of the alga fail to maintain functional (photosynthetic) chloroplasts when cultures are incubated at the moderately elevated temperature of 33° C. Cultures incubated at the elevated temperature for prolonged periods of time irreversibly lose chlorophyll, hence the term bleaching, and the ability to carry out photosynthesis.
The molecular events that unleash the irreversible loss of chloroplasts in Euglena seem to take place long before cultures experience any appreciable loss of chlorophyll. For example, an almost complete loss of chloroplast protein synthesis is evident 24 hours after the onset of treatment at the moderately elevated temperature. Furthermore, loss of transcript for the chloroplast-encoded CP47 and CP43 chlorophyll a-binding apoproteins of photosystem 2 is evident in less that 10 hours.
Our current research focuses on the role of chloroplast chaperones during heat-bleaching. Chaperones are proteins that under normal growth conditions facilitate folding of newly synthesized polypeptides, the translocation of proteins across organellar membranes, and the assembly and disassembly of multimeric complexes. In addition, many chaperones are heat-shock proteins and presumably protect cellular structures from the damaging effects of temperature. Since chaperones play a fundamental role in the biogenesis and continuity of organelles like chloroplasts and mitochondria, is chloroplast chaperone function compromised in Euglena grown at bleaching temperatures?
For more information about this program, contact the Department or Dr. William Ortiz.