In-situ localization and biochemical analysis of bio-molecules reveals Pb-stress amelioration in Brassica juncea L. by co-application of 24-Epibrassinolide and Salicylic Acid

Sukhmeen Kaur Kohli,Shagun Bali,Renu Bhardwaj,Parvaiz Ahmad,Vinod Verma,A A Alqarawi,Ruchi Tejpal,Elsayed Fathi Abd_Allah,Vandana Bhalla

doi:10.1038/s41598-019-39712-2

Sukhmeen Kaur Kohli, Shagun Bali + Show 7 more

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https://doi.org/10.1038/s41598-019-39712-2

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Abstract

Lead (Pb) toxicity is a major environmental concern affirming the need of proper mitigation strategies. In the present work, potential of combined treatment of 24-Epibrassinolide (24-EBL) and Salicylic acid (SA) against Pb toxicity to Brassica juncea L. seedlings were evaluated. Seedlings pre-imbibed in EBL (0.1 mM) and SA (1 mM) individually and in combination, were sown in Pb supplemented petri-plates (0.25, 0.50 and 0.75 mM). Various microscopic observations and biochemical analysis were made on 10 days old seedlings of B. juncea. The toxic effects of Pb were evident with enhancement in in-situ accumulation of Pb, hydrogen peroxide (H2O2), malondialdehyde (MDA), nuclear damage, membrane damage, cell death and polyamine. Furthermore, free amino acid were lowered in response to Pb toxicity. The levels of osmoprotectants including total carbohydrate, reducing sugars, trehalose, proline and glycine betaine were elevated in response to Pb treatment. Soaking treatment with combination of 24-EBL and SA led to effective amelioration of toxic effects of Pb. Reduction in Pb accumulation, reactive oxygen content (ROS), cellular damage and GSH levels were noticed in response to treatment with 24-EBL and SA individual and combined levels. The contents of free amino acid, amino acid profiling as well as in-situ localization of polyamine (spermidine) was recorded to be enhanced by co-application of 24-EBLand SA. Binary treatment of 24-EBL and SA, further elevated the content of osmoprotectants. The study revealed that co-application of combined treatment of 24-EBL and SA led to dimination of toxic effects of Pb in B. juncea seedlings.

Highlights

Www.nature.com/scientificreports nature of Pb, variable symptoms are observed in effected plants including necrosis, chlorosis, growth inhibition, senescence and enhanced generation of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2), superoxide anion (O2−), hydroxyl ion (HO), singlet oxygen (O) and nitric oxide (NO) etc[15,16]
The present study further extended into the few more biochemical parameters including evaluation of oxidative stress, amino acid levels and osmolytes contents and histochemical analysis and is an attempt to better understand the interactive effect of 24-EBL and salicylic acid (SA) in heavy metal stress amelioration
Metal treated seedlings pre-imbibed in 24-EBL and SA, alone and in combination lowered the intensity of green fluorescence

Summary

Introduction

Www.nature.com/scientificreports nature of Pb, variable symptoms are observed in effected plants including necrosis, chlorosis, growth inhibition, senescence and enhanced generation of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2), superoxide anion (O2−), hydroxyl ion (HO), singlet oxygen (O) and nitric oxide (NO) etc[15,16]. Exogenous supplementation with SA to metal stressed plants led to growth promotion and improved photosynthetic efficacy[35,36], reduced ROS levels[37] and altered osmolyte levels[38,39]. It has been studied for its anti-stress potential in tobacco[22], wheat[40], potato[41] and rice[42]. The present study further extended into the few more biochemical parameters including evaluation of oxidative stress, amino acid levels and osmolytes contents and histochemical analysis and is an attempt to better understand the interactive effect of 24-EBL and SA in heavy metal stress amelioration

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