Page 54 - PC2019 Program & Proceedings

PLANT CANADA 2019

PS1. Monday, July 8, morning session at 8:30 am

Dr. Maureen Hanson and Myat T. Lin
Cornell University, NY

Improving photosynthesis in C3 plants

Abstract: Rubisco, which catalyzes the first step in carbon fixation, is a target for efforts to improve
photosynthetic efficiency. Modifying the cellular environment surrounding Rubisco to enhance the CO2
concentration, in order to prevent photorespiration, is one strategy underway in our lab. Another strategy is to
alter the properties of Rubisco itself to increase its enzymatic efficiency and/or to increase its affinity for CO2.
Manajit Hayer-Hartl’s group recently demonstrated assembly of active Rubisco in E. coli, where the effects of
mutagenesis can be quickly examined. Assembly of Rubisco requires multiple chaperones: Cpn60α, Cpn60β and
Cpn20, as well as RbcX, Raf1, Raf2 and BSD2, for assembly of large and small subunits into L8S8 holoenzymes.
We modified Hayer-Hartl’s Arabidopsis vectors to express tobacco Rubisco by replacing the Arabidopsis
assembly factor genes with tobacco ones. We used this system to survey the activity of enzymes comprised of
individual members of the tobacco Rubisco small subunit family, by co-expressing each one with the single
large subunit gene in E. coli. These novel E. coli-expressed Rubisco enzymes have carboxylation kinetics very
similar to that of the native tobacco Rubisco. We also produced tobacco Rubisco with a recently discovered
trichome small subunit in E. coli and found that it has a higher catalytic rate and a lower CO2 affinity compared
to the enzymes with other small subunits.

Bio:

Dr. Maureen Hanson is Liberty Hyde Bailey Professor in the Department of Molecular Biology and Genetics at
Cornell University in Ithaca, NY. She previously was on the Biology faculty at the University of Virginia,
Charlottesville. She holds a Ph.D. in Cell and Developmental Biology from Harvard University, where she
subsequently held an NIH NRSA postdoctoral fellowship. She is a Fellow and recipient of the Lawrence Bogorad
Award of the American Society of Plant Biologists and a Fellow of the American Association for the Advancement
of Science. She received the SUNY Chancellor’s Award for Faculty Service and the Cornell Award for Outstanding
Accomplishments in Basic Research. Her lab is known for identifying the first single dominant fertility restorer
(Rf) gene that suppresses the expression of a toxic mitochondrial gene encoding cytoplasmic male sterility, the
rediscovery of stromules and the demonstration that molecules pass through them between chloroplasts, and
identification of several gene families previously unknown to comprise plant organelle RNA editing machinery.
Her group has ongoing projects concerning improving photosynthetic efficiency through synthesizing the
cyanobacterial carbon-concentrating mechanism in chloroplasts or through engineering of the carbon-fixing
enzyme Rubisco. https://hansonlab.org/

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