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ARS Home » Midwest Area » Urbana, Illinois » Global Change and Photosynthesis Research » Research » Publications at this Location » Publication #218939
Title: Can the cold tolerance of C4 photosynthesis in MiscanthusXgiganteus relative to Zea mays be explained by differences in activities and thermal properties of Rubisco?

Author
item WANG, D - UNIVERSITY OF ILLINOIS
item NAIDU, S - UNIVERSITY OF ILLINOIS
item Portis Jr, Archie
item LONG, S - UNIVERSITY OF ILLINOIS

Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2008
Publication Date: 5/15/2008
Citation: Wang, D., Naidu, S.L., Portis Jr., A.R., Long, S. 2008. Can the cold tolerance of C4 photosynthesis in MiscanthusXgiganteus relative to Zea mays be explained by differences in activities and thermal properties of Rubisco? Journal of Experimental Botany. 59(7):1779-1787.

Interpretive Summary: The cold-tolerant and biofuel feedstock C4 grass Miscanthus x giganteus is exceptional in its productivity in cool climates. Leaves grown at 14 and 25 degrees C exhibit similar photosynthetic responses to temperature, in remarkable contrast to the non-cold-tolerant Zea mays (corn). To contribute to the understanding of the basis of these differences, in this study we compared the temperature responses of the kinetic properties of rapidly extracted and purified Rubisco from cold and warm-grown Miscanthus and Zea mays because Rubisco exerts metabolic control over the light-saturated rate of C4 photosynthesis. The results indicated that the ability of Miscanthus to be productive and maintain photosynthetically competent leaves at low temperature does not result from acclimatory or adaptive change in the properties of Rubisco. This information will benefit scientists attempting to increase the low temperature tolerance of non-cold-tolerant C4 plants like Zea mays.

Technical Abstract: The chilling-tolerant and biofuel feedstock Miscanthus x giganteus (M. x giganteus) is exceptionally productive among C4 grasses in cold climates. It is able to develop photosynthetically active leaves at temperatures 6°C below the minimum for maize. Rubisco exerts metabolic control over the light-saturated rate of C4 photosynthesis. An efficient protocol was developed to purify large amounts of functional Rubisco from C4 leaves. The maximum carboxylation activities (Vmax), activation states, catalytic rates per active site (Kcat) and activation energies (Ea) of purified Rubisco and Rubisco in crude leaf extracts were determined for M. x giganteus grown at 14 and 25ºC, and Zea mays grown at 25ºC. The sequences of the Rubisco small subunit mRNA were also compared. Extracted activities were close to observed rates of CO2 assimilation by the leaves in vivo. On a leaf area basis the extracted activities and activation state of Rubisco did not differ significantly either between the two species, or between growth temperatures. The activation state of Rubisco in leaf extract slightly declined as temperatures decreased, but showed no significant difference between warm and cold-grown M. x giganteus. Although there were a few differences between the species in the translated protein sequences, there were no significant differences in the catalytic properties (Vmax, Kcat, and Ea) for purified Rubisco, nor was there any effect of growth temperature in M. x giganteus. This suggests that the ability of M. x giganteus to be productive and maintain photosynthetically competent leaves at low temperature does not result from acclimatory or adaptive change in the catalytic properties of Rubisco.