COP1 as a key redox-controlled regulator of hypocotyl growth under shade in plants

IGLESIAS MJ; ROJAS, CECILIA COSTIGLIOLO; BIANCHIMMANO LUCIANA; CASAL JJ

Congreso; RAFV Conference 2023 XXXIV Argentinian meeting of Plant Physiology; 2023

Canopy shade enhances the activity of PHYTOCHROME INTERACTING FACTORs (PIFs) to promote auxin synthesis in the cotyledons. Auxin, together with local PIFs and their positive regulator CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1), promote hypocotyl growth to facilitate access to light. Whether shade alters the redox status thereby affecting growth responses, remains unexplored. Here we show that, under shade, high auxin levels increased reactive oxygen (H2O2- O2-.) and nitrogen species (nitric oxide: NO) accumulation in the hypocotyl of Arabidopsis. This nitro-oxidative cellular environment favoured the promotion of hypocotyl growth by COP1 specifically under shade. We demonstrate that COP1 is S-nitrosylated. Impairing this redox regulation enhanced COP1 proteasomal degradation and diminished the intrinsic aptitude of COP1 to interact with target proteins, and its capacity to promote hypocotyl growth. Disabling this regulation also generated transversal asymmetries in hypocotyl growth, indicating poor coordination among different cells, which resulted in random bending and predictably low ability to compete with neighbours