Chloroplast redox status modulates the cell expansion phase of leaf development associated to changes in proteasome activity and endoreduplication index

ARCE ROCÍO; MAYTA MARTÍN; MELZER, MICHAEL; HAJIREZAEI, MOHAMMAD-REZA; LODEYRO, ANABELLA F; CARRILLO, NÉSTOR

Mendoza

Congreso; Congreso SAIB 2022; 2022

Leaf growth is sustained by successive phases of cell proliferation and expansion that determine the final organ size. The rate and extension of these phases are modulated by several developmental and environmental cues. We show herein that changes in the redox status of tobacco chloroplasts caused by introduction of the alternative electron shuttle flavodoxin led to decreased leaf size. Flavodoxin activity as electron sink prevented over-reduction of the photosynthetic electron transport chain and propagation of reactive oxygen species. These effects correlated with significantly lower rates of cell expansion in leaves of flavodoxin-expressing plants. Neither the duration of the expansion phase nor the rate and extension of the proliferative stage were affected by the presence of the alternative electron carrier, resulting in smaller leaf cells without significant differences in their numbers. Cells from transformed plants contained fewer chloroplasts of wild-type size, but their cellular coverage was increased due to cell size reduction. Chloroplast redox modulation of leaf development was associated to increased proteasomal activity and lower endoreduplication. The results identify a new player in the global regulation of plant organ growth, as represented by plastid-generated redox signals, and underscore the value of alternative electron shuttles to investigate the signaling role of chloroplast oxido-reductive biochemistry in plant developmental pathways.