Signaling through reactive oxygen and nitrogen species is differentially modulated in sunflower seedling root and cotyledon in response to various nitric oxide donors and scavengers

Abstract

Sodium nitroprusside (SNP), diethylenetriamine NONOate (DETA), S-nitroso-n-acetyl-D,L- penicillamine (SNAP), and 4-(p-methoxyphenyl)-1,3,2- Oxathiazolylium-5-olate (CAY) exhibit differential NO releasing ability in aqueous solution and hemoglobin is a more efficient NO quencher than cPTIO in solution. DETA releases 16% more NO compared with SNP in solution. Various NO donors (SNP, DETA, SNAP, and CAY) also bring about a differential but concentration-dependent increase in endogenous NO in seedling cotyledons and roots. Two-day old, dark-grown seedling roots exhibit 95%, 77%, 59% and 45% increase in NO content in presence of each of 500 µM of DETA, SNAP, CAY and SNP, respectively, relative to control. NO accumulation in the tissue system as a response to NO donors is reflected in terms of corresponding peroxynitrite accumulation. Release of cyanide and free iron as byproducts of SNP dissociation in solution limits its usefulness as an NO donor. SNP leads to profuse ROS generation in sunflower seedling roots. Light is not a pre-requisite for NO generation from SNP. Present work also demonstrates the usefulness of hemoglobin over cPTIO as NO scavenger. Hemoglobin brings about increasing NO quenching with its increasing concentration from 2.5 to 10 µM. Greater sensitivity of the root system to the NO donor/scavenger treatments is evident, it being in direct contact with the molecules in the incubation/ growth medium. This differential effect does not seem to be significantly transmitted to the cotyledons (long-distance signaling).

Nitric oxide regulates lateral root formation through modulation of ACC oxidase activity in sunflower seedlings under salt stress

“…In order to deplete endogenous NO, hemoglobin was preferentially used as a NO scavenger over cPTIO on the basis of author's recently published work. 50 We have reported that hemoglobin indeed serves as a very efficient NO scavenger to entrap and scavenge tissue NO from the surface of the sunflower seedling roots even though it is not taken up into the system. In contrast, cPTIO proved to be a very bad choice as NO scavenger.…”

Hemoglobin as a probe for estimation of nitric oxide emission from plant tissues

“…Oxygenated hemoglobin (HbO 2 ) is considered as a good choice, and can effectively scavenge NO within concentration range from 125 to 500 µM from both sunflower seedling roots and cotyledons tissue homogenates [21]. The reaction between NO and HbO 2 is rapid, stoichiometric and leads to formation of methemoglobin and nitrate (NO 3− ) [45].…”

“…Thus, a reliable substitute NO quencher is required for various applications. Our recently published observations provided some evidence for the probable role of hemoglobin added in the growth medium on its ability to quench endogenous NO in sunflower seedlings [21, 22].…”

Nitric oxide and light co-regulate glycine betaine homeostasis in sunflower seedling cotyledons by modulating betaine aldehyde dehydrogenase transcript levels and activity

“…GB maintains the equilibrium of K + ions by suppressing Na + uptake through apoplastic route and thus, alleviating stress. [24][25][26] Based on already standardized concentrations of NaCl (120 mM), diethylenetriamine (DETA; 250 μM), and diethyldithiocarbamate (DETC; 250 μM) in the author's laboratory, 27 the present work focuses on examining photomodulation of GB homeostasis, 28,29 as a long-distance signaling response to salt stress in sunflower seedling cotyledons. Modulation of BADH activity 30,31 and transcript 31 levels by nitric oxide (NO) has been proposed to be differentially regulated in light-and dark-grown seedlings, thereby altering GB homeostasis.…”