Abstract
Helianthus annuus L. is an important oilseed crop, which exhibits moderate salt tolerance and can be cultivated in areas affected by salinity. Using patch-clamp electrophysiology, we have characterized Na+ influx and K+ efflux conductances in protoplasts of salt-tolerant H. annuus L. hybrid KBSH-53 under high salinity. This work demonstrates that the plasma membrane of sunflower root cells has a classic set of ionic conductances dominated by K+ outwardly rectifying channels (KORs) and non-selective cation channels (NSCCs). KORs in sunflower show extreme Na+ sensitivity at high extracellular [Ca2+] that can potentially have a positive adaptive effect under salt stress (decreasing K+ loss). Na+ influx currents in sunflower roots demonstrate voltage-independent activation, lack time-dependent component, and are sensitive to Gd3+. Sunflower Na+-permeable NSCCs mediate a much weaker Na+ influx currents on the background of physiological levels of Ca2+ as compared to other species. This suggests that sunflower NSCCs have greater Ca2+ sensitivity. The responses of Na+ influx to Ca2+ correlates well with protection of sunflower growth by external Ca2+ in seedlings treated with NaCl. It can be, thus, hypothesized that NaCl tolerance in sunflower seedling roots is programmed at the ion channel level via their sensitivity to Ca2+ and Na+.
Highlights
Sunflower (Helianthus annuus L.) is an important crop that is widely used in the oil industry and animal feeding
For patch-clamp experiments, sunflower seeds were surface-sterilized with 20% (w/v) Domestos bleach, germinated on wetted filter paper (2 days), and cultivated vertically in filter paper rolls immersed in solution containing 10% standard Murashige and Skoog nutrient medium (MS; Duchefa #M0221, original composition; Murashige and Skoog, 1962), pH 6.0 was adjusted by KOH
Data reported here demonstrate for the first time that H. annuus root plasma membrane has a set of ionic conductances dominated by non-selective cation channels (NSCCs) and K+ outwardly rectifying channels (KORs)
Summary
Sunflower (Helianthus annuus L.) is an important crop that is widely used in the oil industry and animal feeding. Global sunflower production increased more than twice since 2000 (Pilorgé, 2020). It is the third highest oilseed produced in the world, the fourth vegetable oil and the third protein feed source among oilseed crops. Sodium Currents in Sunflower tolerance, their production is affected by high soil salinity, which is common in arid or semi-arid areas (Karrenberg et al, 2006; Li et al, 2020). Important H. annuus L. cultivars survive at 100–150 mM NaCl while some wild sunflower species, such as halophytic Helianthus paradoxus, can withstand much higher levels of NaCl (Karrenberg et al, 2006; Grieve et al, 2012)
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