Interplay of Calcium and Nitric Oxide in improvement of Growth and Arsenic-induced Toxicity in Mustard Seedlings

Abstract

In this study, Ca 2+ mediated no signalling was studied in response to metalloid (As) stress in Brassica seedlings. Arsenic toxicity strongly suppressed the growth (fresh weight, root and shoot length), photosynthetic pigments, Chl a fluorescence indices (Kinetic traits: F v , F m , F v /F o , F m /F o , ФP o or F v /F m , Ψ o , ФE o , PI ABS , Area and N and redox status (AsA/DHA and GSH/GSSG ratios) of the cell; whereas energy flux traits: ABS/RC, TR o /RC, ET o /RC and DI o /RC along with F o , F o /F v , F o /F m , ФD o and S m ) were enhanced. Further, addition of EGTA (Ca 2+ scavenger) and Lacl 3 (plasma membrane ca 2+ channel blocker) to As + ca; while c-ptio (no scavenger) and l-nAMe (no synthase inhibitor) to As + Snp treated seedlings, siezed recovery on above parameters caused due to Ca 2+ and NO supplementation, respectively to As stressed seedlings thereby indicating their signalling behaviour. Further, to investigate the link between ca 2+ and NO, when c-ptio and l-nAMe individually as well as in combination were supplemented to As + ca treated seedlings; a sharp inhibition in above mentioned traits was observed even in presence of ca 2+ , thereby signifying that NO plays crucial role in Ca 2+ mediated signalling. In addition, As accumulation, ROS and their indices, antioxidant system, NO accumulation and thiol compounds were also studied that showed varied results.Arsenic (As) exposure has become a major threat for world agriculture that causes adverse effect on crop productivity by inhibiting cell functioning. The metalloid (As) mainly arises from geothermal weathering of rocks and human activities 1 . The toxicity of As depends on As species. Among the two inorganic species, arsenite (As III ), which prevails in anaerobic environment, enters in plant system through aquaporin channels with greater affinity for thiol groups; while arsenate (As V ) prevalent in aerobic condition/ soil, being analogue of inorganic phosphate (iP), enters via inorganic phosphate transporters, competes with phosphate and replaces phosphate from ATP thereby affecting the energy metabolism of cell 2,3 . Arsenic accumulation causes growth suppression which involves many biochemical and physiological changes in plants including oxidative stress, injuries to membrane and thereby affecting redox state of the cell 4-6 , which is detrimental for plant survival under As toxicity. Additionally, As toxicity negatively regulates chlorophyll (Chl) biosynthesis, PS II photochemistry and ribulose 1,5-bisphosphate carboxylase/ oxygenase (RuBisCO) activity, thereby inhibiting photosynthetic efficiency 6-9 . Previous studies have explicated the prominence of upholding a favourable antioxidants level and redox status of cell to encounter the damage caused due to metalloid exposure 4-6 .Calcium (Ca 2+ ) is a pervasive and pivotal secondary messenger in signal transduction network 10 under both stressed and non-stressed situations. In several studies, it has been shown that Ca 2+ is involved in regulation of plant responses such as photosyn...

Regulatory role of Ca2+ and NO in salicylic acid (SA) induced signaling against Ni2+-induced toxicity in Anabaena sp. PCC 7120

“…These findings suggest the regulatory role of Ca 2+ and NO in SA induced signaling. Our results are in accordance with the earlier findings of Tiwari et al (2018;2019a,b) and Singh et al (2018aSingh et al ( , 2020a in Nostoc muscorum and mustard seedlings, respectively.…”

“…From earlier studies it has been cleared that Ca 2+ plays essential role in regulation of growth, and different physiological processes of plants like stabilizes membrane structures by bonding with phospholipid bilayer, declines ROS levels, enhances key antioxidant enzymes, improves RubisCO activity and CO 2 fixation (Singh et al, 2018a,b;Tiwari et al, 2019a;Verma et al, 2018;Singh et al, 2020a,b), being an essential part of catalytic site of water oxidation (Mn 4 Ca 1 O x Cl y ) of PSII, it helps in the assemblage of water oxidizing complex (OEC) and directly regulates the photosynthetic activity (Andréasson et al, 1995;Bartlett et al 2008;Najafpour et al, 2012;Kalaji et al, 2014;Singh et al, 2018b;Singh et al, 2020a) under stressful environment. NO is also known for improvement in growth by regulating different physiological events like growth, photosynthetic pigments, photosynthetic activities, antioxidants defence system and reduces ROS levels produced by metals/ metalloids either by gene expression through signaling in a molecular cascade or by neutralizing excessive ROS through its free radical functioning (Zhang et al, 2008;Peto 2011;Chen et al, 2013;Xu et al, 2013;Sun et al, 2018;Tiwari et al, 2018;Singh et al, 2020a;Verma et al, 2020). According to a report, NO alleviate salinity stress by promoting photosynthetic rate in eggplant either by improving PSII quantum yield or by splitting excess energy via improving antenna molecules and carotenoid content (Wu et al, 2013).…”

Calcium mediated nitric oxide responses: Acquisition of nickel stress tolerance in cyanobacterium Nostoc muscorum ATCC 27893

“…While PTIO reversed the Ca 2+ mediated betterment of defensive process even in the presence of SNP. Similar to this, Singh et al [ 77 ] have also demonstrated the interactive signaling role of Ca 2+ and NO in up-regulation of antioxidant defense machinery and thereby reduction of ROS accumulation inside the cells of mustard plant, leading to arsenic toxicity alleviation (see Fig. 7 ).…”

Alternative oxidase gene induced by nitric oxide is involved in the regulation of ROS and enhances the resistance of Pleurotus ostreatus to heat stress

“…Previous studies have revealed that NO contributes to various aspects of stress tolerances by influencing ROS metabolism [ 9 ]. Ca 2+ -mediated NO signal transduction is involved in the response of Brassica seedlings to metalloid stress [ 10 ], and in Prunus persica (L.) Batsch, treatment with a NO solution can protect the fruit from pathogen infection by inducing the activity of defense enzymes and the expression of pathogenesis-related genes [ 11 ]. In two ecotypes of reeds, NO significantly reduces the contents of hydrogen peroxide (H 2 O 2 ) and malondialdehyde in calli and significantly inhibits the increase in ion leakage and growth inhibition and decrease in cell viability induced by HS [ 12 ].…”