Plant Growth-Promoting Rhizobacteria Enhance Abiotic Stress Tolerance in Solanum tuberosum Through Inducing Changes in the Expression of ROS-Scavenging Enzymes and Improved Photosynthetic Performance Mayank Anand Gururani • Chandrama Prakash Upadhyaya • Venkidasamy Baskar • Jelli Venkatesh • Akula Nookaraju • Se Won Park Received: 31 March 2012 / Accepted: 5 June 2012 / Published online: 12 August 2012 Ó Springer Science+Business Media, LLC 2012 Abstract In this report we address the changes in the expression of the genes involved in ROS scavenging and ethylene biosynthesis induced by the inoculation of plant growth-promoting rhizobacteria (PGPR) isolated from potato rhizosphere. The two Bacillus isolates used in this investigation had earlier demonstrated a striking influence on potato tuberization. These isolates showed enhanced 1-aminocyclopropane-1-carboxylic acid deaminase activ- ity, phosphate solubilization, and siderophore production. Potato plants inoculated with these PGPR isolates were subjected to salt, drought, and heavy-metal stresses. The enhanced mRNA expression levels of the various ROS- scavenging enzymes and higher proline content in tubers induced by PGPR-treated plants contributed to increased plant tolerance to these abiotic stresses. Furthermore, the photosynthetic performance indices of PGPR-inoculated plants clearly exhibited a positive influence of these bac- terial strains on the PSII photochemistry of the plants. Overall, these results suggest that the PGPR isolates used in this study are able to confer abiotic stress tolerance in potato plants. Keywords Abiotic stress Á PGPR Á Photosynthesis Á ROS Á Solanum tuberosum Introduction Plant growth-promoting rhizobacteria (PGPR) are plant- associated microorganisms that are known to induce plant defenses and confer beneficial effects such as increased plant growth and low susceptibility to diseases caused by pathogens (Kloepper and others 2004a; van Loon and Glick 2004; Dimkpa and others 2009b). PGPR have been proven to counteract the activities of other harmful soilborne microorganisms, thus promoting plant growth (Glick 1995). Some PGPR also elicit physical or chemical chan- ges related to plant defense, a process called ‘‘induced systemic resistance’’ (ISR) (van Loon and Glick 2004). Although it is well known that ISR triggered by PGPR confers resistance against pathogen-induced plant diseases, a few published reports suggest the role of PGPR as elic- itors of abiotic stresses in plants (Yang and others 2009). Strains with plant growth-promoting activity have been identified from various genera of which Pseudomonas and Bacillus are the most extensively studied (Kumar and others 2011). It has been proposed that these bacteria produce phytohormones, antibiotics, and siderophores in the rhizosphere, thus inducing systemic resistance to plant pathogens (Gutierrez-Manero and others 2001; Whipps 2001; Idris and others 2007; Richardson and others 2009). The underlying mechanisms of plant growth promotion by PGPR have been comprehensively described in several articles (van Loon 2007; Kloepper and others 2004b; Yang and others 2009). PGPR belonging to Bacillus spp. are frequently isolated from the rhizosphere, and most have shown favorable effects on plant growth, higher yield, and M. A. Gururani Á V. Baskar Á J. Venkatesh Á S. W. Park (&) Department of Molecular Biotechnology, School of Life & Environmental Sciences, Konkuk University, Seoul 143-701, Korea e-mail: sewpark@konkuk.ac.kr C. P. Upadhyaya Department of Botany, Guru Ghasidas Central University, Bilaspur, CG, India A. Nookaraju Department of Bioenergy Science and Technology, Chonnam National University, 333 Yongbongro, Buk-gu, Gwangju 500-757, Korea 123 J Plant Growth Regul (2013) 32:245–258 DOI 10.1007/s00344-012-9292-6