| Abstract Detail
Photosynthesis(Carbon) Wang, Dafu [1], Portis, Archie R [2], Moose, Stephen P [3], Long, Stephen P. [4]. A molecular explanation of why C4 photosynthesis in Miscanthus, but not maize, can acclimatize to chilling conditions. Miscanthus x giganteus is exceptional among C4 plants in its ability to produce leaves and photosynthesize at low temperature. While the most cold-adapted Zea mays lines show loss of photosynthetic capacity when transferred to 14oC, M. x giganteus shows no loss and can continue photosynthesis down to 8oC. Understanding how this is achieved is critical to adapting Z. mays and other C4 crops to colder climates or allowing them to make use of solar radiation over a longer period of the year. Transgenic analysis of C4 plants has shown that two enzymes share control and are limiting to the light-saturated rate of photosynthesis: Rubisco and Pyruvate Pi Dikinase (PPDK). Previous studies have shown that PPDK is cold labile while others have shown that Rubisco activity at low temperature is likely to constrain photosynthetic rate. Analysis of the sequences for the genes coding for these enzymes in the two species has failed to reveal any differences likely to alter cold-tolerance. Kinetic analysis of the purified enzymes has similarly failed to identify any major differences. However, when Z. mays and M. x giganteus are transferred from 25oC to 14oC, both light-saturated photosynthetic rate (Asat) and maximum quantum yield (Φ) declined by 60% in both species in the first 24hr. In Z. mays it continued to decline in these existing leaves over the next 7 days, but recovered in M. x giganteus. What changes underlie this difference? Within 24hr of the temperature transition after a transient decline the PPDK protein content was seen in M. x giganteus but then steadily increased a few fold over the next days while it declined in the Z. mays leaves. Rubisco levels remained constant in M. x giganteus, but declined slightly in Z. mays. RT-PCR showed that the increase in PPDK protein in the M. x giganteus leaves corresponded to a large increase in mRNA level for PPDK. The results suggest that of the two enzymes know to limit C4 photosynthesis, increase of PPDK and not Rubisco corresponds to the recovery of photosynthetic capacity during low temperature exposure of M. x giganteus. The results suggest a low temperature induction of either transcription of the PPDK gene or inhibition of breakdown of this message in M. x giganteus, but not Z. mays.
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1 - University of Illinois at Urbana-Champaign, Institute of Genomic Biology, Department of Plant Biology, 1201 W Gregory Dr., ERML379, Urbana, IL, 61801, USA
2 - University of Illinois at Urbana-Champaign, Plant Biology, 1201 West Gregory Drive, Urbana, IL, 61801, USA
3 - University of Illinois, Urbana-Champaign, Crop Sciences, 1201 W. Gregory Drive, 389 ERML, Urbana, IL, 61801, USA
4 - University of Illinois at Urbana-Champaign, Institute of Genomic Biology, Department of Plant Biology, Department of Crop Sciences
Keywords:
Miscanthus x giganteus
Photosynthesis
PPDK
rubisco.
Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P13004
Abstract ID:518 |
