Relationship between TCP proteins and protection against photo-oxidative damage during de-etiolation in Arabidopsis thaliana

JURE, ROCÍO M.; ALEM, ANTONELA L.; VIOLA, IVANA L.; GONZALEZ, DANIEL H.

Congreso; LVIII Congreso Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular; 2022

The transition to light is a challenge for dark-germinated seedlings, since light can be harmful to the plant during the greening or de-etiolation process. When the plant grows in dark conditions, the chlorophyll is not synthesized but its precursor, protochlorophyllide, is. The illumination of an etiolated plant directly induces the conversion of the precursor into chlorophyllide, an immediate precursor of chlorophyll, but it also generates a situation of stress and an increase of reactive oxygen species (ROS) due to the illumination of free protochlorophyllide. This can produce photooxidative damage, which affects the accumulation of chlorophyll, photosynthesis and, eventually, the growth or survival of the plant. To avoid photodamage, a number of key regulatory factors are required for the control of chlorophyll biosynthesis during this transition. In this work, we observed that plants with loss-of-function in members of the TEOSINTE BRANCHED 1, CYCLOIDEA, and PROLIFERATING CELL FACTORS (TCP) family of plant transcription factors show increased photodamage and ROS accumulation during de-etiolation. This is correlated with higher levels of protochlorophyllide and increased expression of genes that encode proteins involved in chlorophyll biosynthesis in etiolated plants. The effect of mutation of the TCPs was counteracted by treatment with gibberellin (GA) or overexpression of the transcription factor PHYTOCHROME INTERACTING FACTOR 4 (PIF4), a repressor of the expression of chlorophyll biosynthesis genes, suggesting that the TCPs affect GA metabolism or responses upstream of PIF4. Related to this, mutants in the TCPs show reduced expression levels of genes that encode GA biosynthesis enzymes. Altogether, our results indicate that TCP transcription factors fine-tune the biosynthesis of chlorophyll precursors in etiolated plants and during de-etiolation, affecting GA metabolism and the activity of PIFs.