Suppression of Reactive Oxygen Species Accumulation in Chloroplasts Prevents Leaf Damage but Not Growth Arrest in Salt-Stressed Tobacco Plants

Abstract

Crop yield reduction due to salinity is a growing agronomical concern in many regions. Increased production of reactive oxygen species (ROS) in plant cells accompanies many abiotic stresses including salinity, acting as toxic and signaling molecules during plant stress responses. While ROS are generated in various cellular compartments, chloroplasts represent a main source in the light, and plastid ROS synthesis and/or elimination have been manipulated to improve stress tolerance. Transgenic tobacco plants expressing a plastid-targeted cyanobacterial flavodoxin, a flavoprotein that prevents ROS accumulation specifically in chloroplasts, displayed increased tolerance to many environmental stresses, including drought, excess irradiation, extreme temperatures and iron starvation. Surprisingly, flavodoxin expression failed to protect transgenic plants against NaCl toxicity. However, when high salt was directly applied to leaf discs, flavodoxin did increase tolerance, as reflected by preservation of chlorophylls, carotenoids and photosynthetic activities. Flavodoxin decreased salt-dependent ROS accumulation in leaf tissue from discs and whole plants, but this decline did not improve tolerance at the whole plant level. NaCl accumulation in roots, as well as increased osmotic pressure and salt-induced root damage, were not prevented by flavodoxin expression. The results indicate that ROS formed in chloroplasts have a marginal effect on plant responses during salt stress, and that sensitive targets are present in roots which are not protected by flavodoxin.

Reactive oxygen species generated in chloroplasts contribute to tobacco leaf infection by the necrotrophic fungus Botrytis cinerea

“…In this regard, chloroplast‐generated ROS are involved in HR‐like cell death processes mediated by a mitogen‐activated protein kinase cascade (Liu et al ., ), and were also shown to contribute to LCD in tobacco leaves infected by the hemibiotrophic bacterium Xcv (Zurbriggen et al ., ); however, the role of chloroplastic ROS in plant responses to necrotrophs has not been investigated so far. Transgenic tobacco plants expressing a plastid‐targeted cyanobacterial Fld accumulate lower ROS levels than WT plants in response to diverse stress factors (Tognetti et al ., ; Lodeyro et al ., ). In the present work, we used these genetically modified tobacco lines to analyze the role of chloroplastic ROS in plant responses to the necrotrophic fungus B. cinerea .…”

Whole-Plant Metabolic Allocation Under Water Stress

“…Increases in phenolics under water stress may be explained partly by their function as antioxidants ( Nakabayashi et al, 2014 ), a function that may in fact be less necessary in roots than in leaves, because roots lack the spikes in reactive oxygen species under stress that are associated with chloroplasts ( e.g. , Lodeyro et al, 2016 ). Many important secondary metabolites (e.g., alkaloids and flavonoids) known to be produced in roots ( van Dam, 2009 ) were not measured in studies considering the effects of water stress.…”

Effects of Various Light-Emitting Diode (LEd) Wavelengths on the Growth of Scenedesmus Obliquus Fachb-12 and Accumulation of Astaxanthin

“…The steady-state level of ROS is dependent on the ROS gene network [52,53]. Although the ROS gene network has a key role in various biological processes, the detailed function of only few genes were determined until now in plants [52,54,55]. Here, we found that high amounts of ROS might induce the accumulation of astaxanthin under blue light.…”