Cytochrome c levels modulate plant growth, carbohydrate metabolism and gibberellin responses in Arabidopsis thaliana

WELCHEN E; RACCA S; GONZALEZ DH

Conferencia; International Conference Plant Mitochondrial Biology (ICPMB); 2017

Cytochrome c (CYTc) is a heme protein of the mitochondrial intermembrane space that mediates electron transfer between Complexes III and IV of the respiratory chain. We studied the effect of reducing CYTc levels on vegetative growth in Arabidopsis thaliana. Plants with reduced CYTc levels are smaller and reach flowering several days later but with the same number of leaves than wild-type plants. These plants accumulate higher levels of starch and glucose during the day and this is correlated with changes in the expression of sugar-responsive genes. Treatment with gibberellins abolishes the delay in flowering time and reduces glucose accumulation and the induction of sugar-responsive genes at the beginning of the day. This suggests that a decrease in CYTc levels may cause changes in gibberellin homeostasis. In agreement with this, plants with reduced CYTc levels contain higher levels of DELLA proteins, which act as repressors of gibberellin responses and whose degradation is triggered by gibberellins. Also, increasing the amount of CYTc in plants decreases the levels of DELLA proteins, enhances growth and accelerates flowering. These effects of CYTc require active gibberellin synthesis, since they are not observed in a gibberellin-deficient mutant. We propose that CYTc establishes a link between metabolic and hormonal pathways related to plant growth.