AUGMENTED FERREDOXIN LEVELS IN TRANSPLASTOMIC TOBACCO PLANTS COUPLE ALTERNATIVE ELECTRON FLOW WITH ENDOGENOUS PHOTOPROTECTIVE MECHANISMS

LOBAIS, CELINA; BILGER, WOLFGANG; BLANCO, NICOLÁS E

Congreso; Reunión Conjunta SAIB-SAMIGE 2020; 2020

SAIB-SAMIGE

Transplastomic tobacco plants overexpressing the minor pea Ferredoxin (Fd) isoform (OeFd plants) were originally generated to increase the availability of soluble electron transporters at the acceptor-side of Photosystem I. Unexpectedly, these plants exhibited a puzzling variegated phenotype, reduced growth and increased non-photochemical quenching (NPQ) when grown under greenhouse conditions (150 µmol m-2 s-1) (Blanco et al., 2013). Moreover, the photosynthetic analysis of OeFd plants demonstrated that green tissues of mature leaves exhibited less photosynthetic yield in both photosystems than their wild-type counterparts. Altogether, these results suggest that the variegated-leaf phenotype of OeFd plants might be linked to cells with abnormally developed chloroplasts due to redox imbalance in the photosynthetic electron transport chain (PETC). To gain insight in the PSI activity of OeFd plants,4-week-old plants growing under the described greenhouse conditions were shifted to higher and lower illumination intensities, and evaluated in their photosynthetic parameters. Contrary to the common behaviour of variegated-leaf mutants, OeFd plants did not exhibit an improvement in growth rate and neither in PSI and PSII functionality at lower light intensities. On the other hand, transgenic plants shifted to higher light intensities increased their growth rate (number of leaves generated after the light intensity change) and PSII functionality. Based on the analysis of the photosynthetic parameters of plants growing under the three different light conditions, we propose that OeFd plants might be perceiving the greenhouse conditions as an ?apparent? light-limitation. According to this scenario, alien Fd has an exceptional capacity to ?compete? for reducing equivalents with the endogenous tobacco Fd in OeFd plants. Furthermore, the augmented sink capacity conferred by a plant Fd isoform in our approach is coupling this alternative photosynthetic electron flow with the endogenous photoprotective mechanisms. To sum up, the flexibility that augmented Fd levels confer to PSI activity emerges as a promising strategy to produce climate-resilient plants.