Bacillus amyloliquefaciens Confers Tolerance to Various Abiotic Stresses and Modulates Plant Response to Phytohormones through Osmoprotection and Gene Expression Regulation in Rice.

Puneet S Chauhan,Shalini Tiwari,Charu Lata,Vivek Prasad

doi:10.3389/fpls.2017.01510

Abstract

Being sessile in nature, plants have to withstand various adverse environmental stress conditions including both biotic and abiotic stresses. Comparatively, abiotic stresses such as drought, salinity, high temperature, and cold pose major threat to agriculture by negatively impacting plant growth and yield worldwide. Rice is one of the most widely consumed staple cereals across the globe, the production and productivity of which is also severely affected by different abiotic stresses. Therefore, several crop improvement programs are directed toward developing stress tolerant rice cultivars either through marker assisted breeding or transgenic technology. Alternatively, some known rhizospheric competent bacteria are also known to improve plant growth during abiotic stresses. A plant growth promoting rhizobacteria (PGPR), Bacillus amyloliquefaciens NBRI-SN13 (SN13) was previously reported by our lab to confer salt stress tolerance to rice seedlings. However, the present study investigates the role of SN13 in ameliorating various abiotic stresses such as salt, drought, desiccation, heat, cold, and freezing on a popular rice cv. Saryu-52 under hydroponic growth conditions. Apart from this, seedlings were also exogenously supplied with abscisic acid (ABA), salicylic acid (SA), jasmonic acid (JA) and ethephon (ET) to study the role of SN13 in phytohormone-induced stress tolerance as well as its role in abiotic and biotic stress cross-talk. All abiotic stresses and phytohormone treatments significantly affected various physiological and biochemical parameters like membrane integrity and osmolyte accumulation. SN13 also positively modulated stress-responsive gene expressions under various abiotic stresses and phytohormone treatments suggesting its multifaceted role in cross-talk among stresses and phytohormones in response to PGPR. To the best of our knowledge, this is the first report on detailed analysis of plant growth promotion and stress alleviation by a PGPR in rice seedlings subjected to various abiotic stresses and phytohormone treatments for 0, 1, 3, 10, and 24 h.

Highlights

Rice (Oryza sativa L.) is the second most important staple crop across the globe having high caloric value
In order to analyze the effects of SN13 on various biochemical parameters, rice seedlings were collected at different time points of various abiotic stresses namely, salt, drought, desiccation, heat, cold, and freeze, and phytohormone treatments viz. abscisic acid (ABA), salicylic acid (SA), jasmonic acid (JA), and ethephon after 1, 3, 10, and 24 h with or without SN13-inoculation
Taken together our results indicate that the abiotic stress amelioration capacity of rice seedlings have been significantly improved with SN13-inoculation under all stresses

Summary

Introduction

Rice (Oryza sativa L.) is the second most important staple crop across the globe having high caloric value Various abiotic stresses such as salt, drought, and extreme temperatures, and biotic stresses are major threats for agricultural production and productivity worldwide. Abiotic stresses are reported to adversely affect the yields of staple food crops by 70% (Kaur et al, 2008; Mantri et al, 2012). Crop responses to these environmental stresses are manifested at physiological, biochemical and molecular levels from the early stage of seed germination to maturity and senescence. It has been well documented that the genes expressed under various abiotic stresses help in improving cellular tolerance by maintaining osmotic homeostasis and by regulating stress responsive gene expression (Lata et al, 2015; Tiwari et al, 2017)

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