Decreased levels of thioredoxin o1 influences stomatal development and aperture but not photosynthesis under non-stress and saline conditions

This article belongs to the Special Issue Antioxidant Metabolic Pathways in Plants 2.0Salinity has a negative impact on plant growth, with photosynthesis being downregulated partially due to osmotic effect and enhanced cellular oxidation. Redox signaling contributes to the plant response playing thioredoxins (TRXs) a central role. In this work we explore the potential contribution of Arabidopsis TRXo1 to the photosynthetic response under salinity analyzing Arabidopsis wild-type (WT) and two Attrxo1 mutant lines in their growth under short photoperiod and higher light intensity than previous reported works. Stomatal development and apertures and the antioxidant, hormonal and metabolic acclimation are also analyzed. In control conditions mutant plants displayed less and larger developed stomata and higher pore size which could underlie their higher stomatal conductance, without being affected in other photosynthetic parameters. Under salinity, all genotypes displayed a general decrease in photosynthesis and the oxidative status in the Attrxo1 mutant lines was altered, with higher levels of H2O2 and NO but also higher ascorbate/glutathione (ASC/GSH) redox states than WT plants. Finally, sugar changes and increases in abscisic acid (ABA) and NO may be involved in the observed higher stomatal response of the TRXo1-altered plants. Therefore, the lack of AtTRXo1 affected stomata development and opening and the mutants modulate their antioxidant, metabolic and hormonal responses to optimize their adaptation to salinity.This research was funded by Spanish grants MINECO/FEDER (BFU2017-86585-P and PGC2018-093824-B-C41), MINECO/ERDF (CTM2014-53902-C2-1-P), and Seneca Excellence Project (19876/GERM/15). ASG and SDV were supported by FPI grants from MINECO. MN was supported by a predoctoral fellowship BES-2015- 072578 from MINECO, Spain co-financed by the European Social Fund (ESF). IFS received funding from the European Union’s Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie grant agreement Nº 753301.Peer reviewe