CHLOROPLAST REDOX STATE MODULATES LEAF DEVELOPMENT AND NATURAL SENESCENCE IN FLAVODOXIN-EXPRESSING PLANTS

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

Montpellier

Congreso; International Plant Molecular Biology 2018; 2018

Leaf growth proceeds through different developmental phases. The first phase is dominated by proliferation, the second by cell expansion followed by maturation and finally, senescence of the leaf. During the proliferative phase, the photosynthetic electron transport chain (PETC) is in process of formation and at the opposite stage of leaf development, senescence, chloroplasts dismantling collapse PETC. N on-functional PETC suffers photooxidative stress, leading to reactive oxygen species (ROS) production. ROS play signaling roles in both leaf development and senescence, but their subcellular source is not completely clarified. It has been shown that a plastid-targeted flavodoxin (Fld) prevents ROS accumulation in chloroplast of transgenic tobacco lines, acting as an antioxidant specific for these organelles. Fld-expressing plants showed smaller leaves caused by a repression of cell expansion, whereas cell proliferation was unaffected. Additionally, the natural senescence of Fld-expressing plants is delayed. Leaves of these plants remained green by extended preservation of pigments, and exhibited higher photosynthetic activity and lower ROS accumulation in chloroplasts. Fld expression also delayed the inhibition of central metabolic routes in senescent leaves, as reflected by higher levels of key aminoacids and phosphorylated sugars. Altogether, t he results indicate that chloroplast redox state is involved in leaf development and senescence.