UNCOUPLING THE ROLES OF CHLOROPLAST REDOX STATE IN LEAF DEVELOPMENT AND STRESS TOLERANCE THROUGH REGULATED EXPRESSION OF A FLAVODOXIN

MAYTA, MARTÍN L.; DEMARCHI, MARIANA; CARRILLO, NÉSTOR; SAENZ, MARÍA MERCEDES; LODEYRO, ANABELLA F.

Salta

Congreso; LV Annual SAIB Meeting and XIV PABMB Congress; 2019

Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular (SAIB)

In higher plants the processes of cell proliferation and expansion are responsible for determining the final size of leaves. Moreover, leaf size directly influences yield by affecting photosynthates production, which has important agronomic implications. Homeostasis of reactive oxygen species (ROS) has a central role in the regulation of cell expansion during leaf growth. In leaves, most ROS come from chloroplasts. Theinfluence of ROS in cellular processes is regulated by a tight balance between their production and scavenging by antioxidant systems. Flavodoxin (Fld) is an electronic carrier isofunctional with ferredoxin (Fd). Fld is present in both algae and cyanobacteria, but absent in higher plants. Constitutive expression of a plastid-targeted can increase tolerance to multiple stresses in plants by acting as a general antioxidant specific for chloroplasts. Therefore Fld-expressing lines can be used as tools to probe the role played by chloroplast-generated ROS in different biological processes. However, constitutive expression of Fld also results in smaller leaves. The main objective of this work is to elucidate ifenhanced stress tolerance and reduction of leaf size are related, by expressing Fld under the control of developmental and stress-inducible promoters. Transgenic Arabidopsis thaliana plants expressing Fld constructs under the control of cell proliferation or cell expansion- specific promoters were obtained using the floral dip technique. Additionally, plants expressing Fld under the control of two stress-inducible promoters, PEC and PEC:I, which differ in their expression strength, were obtained. Similar constructs containing the reporter gene β-glucuronidase (GUS) were used to set up the conditions of induction. NaCl and abscisic acid (ABA) were used as inducers for stress-inducible promoters, both in 15-day seedlings and in leaf discs from adult plants. Moreover, leaf size, cell size and cell numbers were determined in non-stressed plants. Fld expression was confirmed by Western blot assays in the different stages of leaf development and under stress conditions in all lines. Preliminary results obtained provide clues to understand how chloroplast redox state determines leaf size affecting in final instance the crop yield.