J Integr Plant Biol. ›› 2013, Vol. 55 ›› Issue (8): 721-734.DOI: 10.1111/jipb.12047

• Plant-environmental Interactions • Previous Articles     Next Articles

Photosynthetic and Molecular Markers of CO2-mediated Photosynthetic Downregulation in Nodulated Alfalfa

Álvaro Sanz-Sáez1,4†*, Gorka Erice1, Iker Aranjuelo2, Ricardo Aroca3, Juan Manuel Ruíz-Lozano3, Jone Aguirreolea1, Juan José Irigoyen1 and Manuel Sanchez-Diaz1   

  1. 1Departamento de Biología Vegetal, Sección Biología Vegetal (Unidad Asociada al CSIC, EEAD, Zaragoza e ICVV, Logroño), Facultades de Ciencias y Farmacia, Universidad de Navarra, c/ Irunlarrea 1, Pamplona, Navarra, Spain
    2Instituto de Agrobiotecnología, Universidad Pública de Navarra-CSIC-Gobierno de Navarra, Campus de Arrosadía, E-31192.Mutilva Baja, Spain
    3Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín(CSIC), Profesor Albareda 1, E-18008 Granada, Spain
    4Departamento de Biologín Vegetal, Unidad de Fisiología Vegetal, Universidad de Barcelona, Av. Diagonal 645, E-8028, Spain
  • Received:2012-10-30 Accepted:2013-02-24 Published:2013-06-24
  • About author:*Corresponding author Fax: +34 934 112 842; E-mail: alvaro_ssj@hotmail.com


Elevated CO2 leads to a decrease in potential net photosynthesis in long-term experiments and thus to a reduction in potential growth. This process is known as photosynthetic downregulation. There is no agreement on the definition of which parameters are the most sensitive for detecting CO2 acclimation. In order to investigate the most sensitive photosynthetic and molecular markers of CO2 acclimation, the effects of elevated CO2, and associated elevated temperature were analyzed in alfalfa plants inoculated with different Sinorhizobium meliloti strains. Plants (Medicago sativa L. cv. AragÓn) were grown in summer or autumn in temperature gradient greenhouses (TGG). At the end of the experiment, all plants showed acclimation in both seasons, especially under elevated summer temperatures. This was probably due to the lower nitrogen (N) availability caused by decreased N2-fixation under higher temperatures. Photosynthesis measured at growth CO2 concentration, rubisco in vitro activity and maximum rate of carboxylation were the most sensitive parameters for detecting downregulation. Severe acclimation was also related with decreases in leaf nitrogen content associated with declines in rubisco content (large and small subunits) and activity that resulted in a drop in photosynthesis. Despite the sensitivity of rubisco content as a marker of acclimation, it was not coordinated with gene expression, possibly due to a lag between gene transcription and protein translation.

Sanz-Sáez Á, Erice G, Aranjuelo I, Aroca R, Ruíz-Lozano JM, Aguirreolea J, Irigoyen JJ, Sanchez-Diaz M (2013) Photosynthetic and molecular markers of CO2-mediated photosynthetic downregulation in nodulated alfalfa. J. Integr. Plant Biol. 55(8), 721–734.

Key words: Carbon dioxide, Medicago sativa (alfalfa), Photosynthetic down-regulation, RbcL and RbcS, Sinorhizobium meliloti

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