Abstract
Low temperature is one of the most important factors affecting plant growth, it causes an stress that directly alters the photosynthetic process and leads to photoinhibition when severe enough. In order to address the photosynthetic acclimation response of Lotus japonicus to cold stress, two ecotypes with contrasting tolerance (MG-1 and MG-20) were studied. Their chloroplast responses were addressed after 7 days under low temperature through different strategies. Proteomic analysis showed changes in photosynthetic and carbon metabolism proteins due to stress, but differentially between ecotypes. In the sensitive MG-1 ecotype acclimation seems to be related to energy dissipation in photosystems, while an increase in photosynthetic carbon assimilation as an electron sink, seems to be preponderant in the tolerant MG-20 ecotype. Chloroplast ROS generation was higher under low temperature conditions only in the MG-1 ecotype. These data are consistent with alterations in the thylakoid membranes in the sensitive ecotype. However, the accumulation of starch granules observed in the tolerant MG-20 ecotype indicates the maintenance of sugar metabolism under cold conditions. Altogether, our data suggest that different acclimation strategies and contrasting chloroplast redox imbalance could account for the differential cold stress response of both L. japonicus ecotypes.
Highlights
Suboptimal temperature is one of the most important abiotic factors limiting plant growth
A discriminant analysis of the chloroplast proteome was carried out in the MG-1 and MG-20 L. japonicus ecotypes exposed to low temperature
Proteins related with nitrogen and carbon metabolism, highlighting saccharose and starch metabolism were more abundant in the MG-20 ecotype
Summary
Suboptimal temperature is one of the most important abiotic factors limiting plant growth. Cold acclimation can be defined as the modifications of anatomy, physiology and metabolism that occur in response to sub-optimum temperatures that minimize irreversible freeze-damage and improve plant fitness. This process implies massive changes in gene expression[2,3], enzymatic activities[4], proteomic changes[5] and subcellular reprogramming of metabolism[6]. Photosystems, electron transport chain, as well as the Calvin-Benson cycle and other carbon metabolisms reactions, are involved in the production of carbohydrates during photosynthesis This complex process is finely regulated through different signals, allowing its homeostasis under different environmental conditions. The degree of participation of these organelles in the cold stress response in legumes is poorly studied
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