Keerberg Olav, Pärnik Tiit, Ivanova Hiie, Bassüner Burgund, Bauwe Hermann
Department of Plant Physiology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51014 Tartu, Estonia
Department of Plant Physiology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51014 Tartu, Estonia.
J Exp Bot. 2014 Jul;65(13):3649-56. doi: 10.1093/jxb/eru239. Epub 2014 Jun 10.
Formation of a photorespiration-based CO2-concentrating mechanism in C3-C4 intermediate plants is seen as a prerequisite for the evolution of C4 photosynthesis, but it is not known how efficient this mechanism is. Here, using in vivo Rubisco carboxylation-to-oxygenation ratios as a proxy to assess relative intraplastidial CO2 levels is suggested. Such ratios were determined for the C3-C4 intermediate species Flaveria pubescens compared with the closely related C3 plant F. cronquistii and the C4 plant F. trinervia. To this end, a model was developed to describe the major carbon fluxes and metabolite pools involved in photosynthetic-photorespiratory carbon metabolism and used quantitatively to evaluate the labelling kinetics during short-term (14)CO2 incorporation. Our data suggest that the photorespiratory CO2 pump elevates the intraplastidial CO2 concentration about 3-fold in leaves of the C3-C4 intermediate species F. pubescens relative to the C3 species F. cronquistii.
在C3 - C4中间植物中形成基于光呼吸的二氧化碳浓缩机制被视为C4光合作用进化的先决条件，但尚不清楚这种机制的效率如何。本文建议使用体内Rubisco羧化与氧化比率作为评估相对质体内二氧化碳水平的指标。测定了C3 - C4中间物种柔毛黄菊与亲缘关系密切的C3植物克氏黄菊和C4植物三脉黄菊的这种比率。为此，建立了一个模型来描述光合 - 光呼吸碳代谢中涉及的主要碳通量和代谢物库，并定量用于评估短期（14）CO2掺入期间的标记动力学。我们的数据表明，相对于C3物种克氏黄菊，光呼吸二氧化碳泵使C3 - C4中间物种柔毛黄菊叶片中的质体内二氧化碳浓度提高了约3倍。
