Singlet Oxygen Plays an Essential Role in the Root’s Response to Osmotic Stress

Abstract

As SOSG fluorescence indicated the presence of singlet oxygen both before and after cell death, it is important to consider whether the appearance of singlet oxygen is an essential component of PEG-induced . Relationship between integrity of the quiescent center and root elongation. A, Fluorescence resulting from SCR::GFP expression in the endodermis and quiescent center. Roots were exposed to 30% PEG for 1 to 8 h and counterstained with propidium iodide (PI). The median plane was imaged where opaque regions in PI staining indicate cell death. Arrows indicate the quiescent center; scale bars, 100 μm. B, Root elongation rate following exposure to PEG. Student's t test, alpha = 0.05; difference in letters signifies a P < 0.05 significant difference; error bars are se, n ≥ 13. stress response or a symptom of cell death. In the former possibility, singlet oxygen would play a direct role in the PEG responses, and specific scavengers of singlet oxygen should mitigate its action. To test this, His, a membrane-permeable specific scavenger of singlet oxygen, was employed. His rapidly forms specific endoperoxides in the presence of singlet oxygen. It is a weaker scavenger of hydroxyl radicals and hydrogen peroxide and does not scavenge superoxide (Matheson et al., 1975; Cai et al., 1995; Ishibashi et al., 1996). The specificity of His as a scavenger for singlet oxygen as opposed to the other ROS is shown in Supplemental Figure S6. As indicated in Figure 6, A and B, His readily mitigates the appearance of singlet oxygen as measured by SOSG. Significantly, the amount of cell death was reduced by 50% ( Fig. 6B) and, as shown in Figure 6C, the presence of His alleviated the repression of the rate of root elongation by PEG. In all, the results lend support for an active role of singlet oxygen in the response to osmotic stress.The light-independent origin of singlet oxygen is unclear. SHAM is a nonspecific inhibitor of mitochondrial Composite of multiple confocal images of ROS accumulation in root tips exposed to 30% PEG for different durations. A, Composite of confocal images that were collated for each specific signal (ROS probes and propidium iodide stain). Multiple image acquisitions for each time point were aligned manually by rotation and overlaid to create the average composite image using Matlab script. The Look Up Table was set to "Fire" and scaled to maximum as white and minimum as blue. Shown are 1 O 2 , measured using the SOSG probe; NO, measured using the DAF-FM-AM probe; O − 2, measured using the BesSo-AM probe; H 2 O 2 , measured using the Bes-H 2 O 2 -AC probe, and cell permeability, measured using staining by propidium iodide. B, Schematic representation of the fluorescence shown in A. Scale bar, 100 µm. Figure 5. Singlet oxygen-and hydrogen peroxide-specific gene expression in roots. A, Transcript levels were measured by RT-qPCR analysis at 0, 1, 2, and 3 h after treatment with 30% PEG. B, Specificity of gene expression. The transcript level fold change in roots; no treatment (Control); treatment for 2 h in ...

Negative Roles of Strigolactone-Related SMXL6, 7 and 8 Proteins in Drought Resistance in Arabidopsis

“…These results suggested that SMXL6, 7 and 8 genes were involved in the regulation of mechanisms associated with, at least, these investigated drought resistance-related traits. An increase in cell membrane integrity can help plants prevent leaf water loss as reported by various studies [55][56][57][58]. Furthermore, the higher leaf surface temperatures observed in smxl6,7,8 mutant plants in comparison with WT plants under both well-watered and water-deficit conditions supported the reduced leaf water transpiration from the smxl6,7,8 mutant versus WT plants (Figure 3a-c).…”

Laterals take it better – Emerging and young lateral roots survive lethal salinity longer than the primary root in Arabidopsis

“…The vital stains Fluorescein diacetate (FDA, Sigma) and Propidium Iodide (PI, Sigma) were applied simultaneously as reported by 52 . Cell viability was also determined in SCR::GFP plants as reported by 53 . The fluorescent signals were detected by laser scanning confocal microscope -LSM710 (Zeiss) with a Plan-Apochromat 20 ×0.8 numerical aperture air objective lens.…”

Methodology of Drought Stress Research: Experimental Setup and Physiological Characterization

“…Under soil drying conditions, this is impossible as soil Ψw changes continuously along with water evaporation and consumption by a plant. On the other hand, due to interference of PEG with root integrity [78], this equilibrium is also hardly achievable in aqueous PEG solutions (especially when PEG concentration is high). Thus, the agar-based model system currently is an ideal choice to address dehydration avoidance and mechanisms of dehydration tolerance [10].…”