Rutin, a flavonoid with antioxidant activity, improves plant salinity tolerance by regulating K+ retention and Na+ exclusion from leaf mesophyll in quinoa and broad beans

Abstract

The causal relationship between salinity and oxidative stress tolerance is well established, but specific downstream targets and the role of specific antioxidant compounds in controlling cellular ionic homeostasis remains elusive. In this work, we have compared antioxidant profiles of leaves of two quinoa genotypes contrasting in their salt tolerance, with the aim of understanding the role of enzymatic and non-enzymatic antioxidants in salinity stress tolerance. Only changes in superoxide dismutase activity were correlated with plant adaptive responses to salinity. Proline accumulation played no major role in either osmotic adjustment or in the tissue tolerance mechanism. Among other non-enzymatic antioxidants, rutin levels were increased by over 25 fold in quinoa leaves. Exogenous application of rutin to glycophyte bean leaves improved tissue tolerance and reduced detrimental effects of salinity on leaf photochemistry. Electrophysiological experiments revealed that these beneficial effects were attributed to improved potassium retention and increased rate of Na+ pumping from the cell. The lack of correlation between rutin-induced changes in K+ and H+ fluxes suggest that rutin accumulation in the cytosol scavenges hydroxyl radical formed in response to salinity treatment thus preventing K+ leak via one of ROS-activated K+ efflux pathways, rather than controlling K+ flux via voltage-gated K+-permeable channels.

Making Plants Break a Sweat: the Structure, Function, and Evolution of Plant Salt Glands

“…NaCl sequestration capacity may be the most critical function of salt bladders in young leaves of Aizoaceae and Amaranthaceae halophytes (Agarie et al, 2007; Bonales-Alatorre et al, 2013; Barkla et al, 2016), but as the leaf matures and the salt bladders reach their maximum volume, salt sequestration rate needs to be paused (Adams et al, 1998; Jou et al, 2007; Barkla and Vera-Estrella, 2015; Oh et al, 2015). Other functions including providing a secondary epidermal layer to protect against water loss, UV stress, and also serving as reserves for ROS scavenging metabolites and organic osmoprotectants may contribute more to plant survival under abiotic stress as the leaf matures (Adolf et al, 2013; Barkla and Vera-Estrella, 2015; Ismail et al, 2015; Oh et al, 2015). The corresponding increased rate of salt secretion as a response to increasing concentrations of soil NaCl is also observed for salt glands in other plant clades (Marcum et al, 1998; Mishra and Das, 2003).…”

Saponin seed priming improves salt tolerance in quinoa

“…Osmotic adjustment for survival of plants under high salinity is linked to K + retention, and restricting high Na + accumulation in cytosol, this desirable adjustment also occurred due to saponin priming in this study (Figure ) depicted by high K + and low leaf Na + contents. The improved K + retention in leaf might be occurred due to activation of antioxidants such as phenols (Ismail et al., ). Ismail et al.…”

“…Ismail et al. () reported that exogenously applied rutin (a leaf phenol), improved K + retention accompanied by Na + pumping out of cell as indicated by strict control over voltage‐gated channels, thus maintaining proper water relations along with avoidance of Na + toxicity and appropriate K + /Na + ratio (Figure ). This K + /Na + ratio rather than alone Na + concentration has been widely considered as index of salinity tolerance (Houshmand, Arzani, Maibody, & Feizi, ).…”

“…Ismail et al. () reported that antioxidant scavenging also improves K + retention in cytosol and accelerate Na + pumping out of cell. Furthermore, saponins are composed of sugars and secondary metabolites, that is steroids and terpenes.…”

Determination of phenolic acids and rutin inHeliotropium thermophilumby high-performance liquid chromatography with photodiode array detection

“…[45] Among other non-enzymatic antioxidants, rutin levels were increased by over 25 fold in quinoa leaves under salinity stress. [46] In conditions. The rutin concentration increased more than three times.…”