CYTOCHROME C REGULATES HORMONE-MEDIATED HYPOCOTYL ELONGATION IN ARABIDOPSIS.

GRASS, DIANA; CANAL, M VICTORIA; MANSILLA, NATANAEL; WELCHEN, ELINA; GONZALEZ, DANIEL H

Congreso; LVIII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research; 2023

Energy production through oxidative phosphorylation is one of the main processes that take place inside mitochondria. Oxidative phosphorylation is performed by the sequential operation of complexes (I–V) located in the inner mitochondrial membrane. In addition to these complexes, Cytochrome c (CYTc) catalyzes the transfer of electrons from complex III to complex IV. Phenotypic analysis of mutant and overexpression lines suggested that CYTc is a positive regulator of hypocotyl elongation. Changes in hypocotyl growth mainly result from changes in longitudinal cell elongation. Accordingly, cytc mutants show a decrease in hypocotyl cell length, relative to the wild type. We show that the defect in cytc mutants is rescued by exogenous application of brassinosteroid (BR) and auxin (AUX). In addition, cytc mutants exhibit altered sensitivity to a BR biosynthesis inhibitor and the polar auxin transport inhibitor NPA, suggesting that AUX and BR homeostasis are affected. The gain-of-function mutation bzr1-1D suppresses the elongation defect of cytc mutants indicating that BZR1 acts downstream of CYTc in promoting plant growth. Previous studies have shown that BZR1 directly interacts with PIF4, and this complex controls cell elongation and hypocotyl growth. Our results suggest that CYTc is capable of regulating the elongation of Arabidopsis hypocotyls acting via the BZR1–PIF4 complex.