CONICET | Buscador de Institutos y Recursos Humanos

Transplastomic tobacco plants overexpressing the minor pea Ferredoxin (Fd) isoform (OeFd1) were originally generated to increase the availability of soluble electron transporters at the acceptor-side of Photosystem I (PSI) (Blanco et al., 2013). Besides having an augmented amount of soluble acceptor carriers in the stroma, these plants exhibited unexpectedly lower linear electron flow (LEF) than control plants, a variegated phenotype, reduced growth as well as increased non-photochemical quenching (NPQ) under normal light intensities (150 μmol m-2 s-1). The patchy chlorophyll distribution in leaves was linked to cells with abnormally developed chloroplasts and suggested an effect of the redox status of Photosystem I (PSI) in plant cell development. To gain insight into the underlying mechanism that provokes this phenotype, we evaluated the response of one-month-old variegated OeFd1 plants to changes in the growth light intensity and studied the performance of their 56photosynthetic electron transport chain (PETC). Four-week-old OeFd1 plants shifted to lower growth-light intensity did not exhibit an improvement in growth rate neither in PSII and PSI functionality. Moreover, a physiological chlorophyll response to a decrease in light intensity was not observed in OeFd1 plants and leaf phenotype remained variegated. In contrast, transgenic plants shifted to higher light intensities increased their growth rate (number of leaves generated after the light intensity change), LEF and PSII functionality. When compared with wild-type siblings, OeFd1 plants had a better photosynthetic performance, especially at PSII. Altogether, these results confirm the importance of the regulation of the PSI redox status for plant growth and chloroplast development and present a novel strategy to improve photoprotective mechanisms based on the manipulation of electron partitioning at the PSI acceptor-