Alleviation of environmental stress in plants: The role of beneficial Pseudomonas spp

Environmental stress factors, such as heavy metals, salinity, and drought, have been increasing steadily over the last few decades, and have negative effects on plant health and productivity. Under such conditions, certain Pseudomonas spp. colonized plant roots or tissue interior can alleviate the effects of environmental stresses on plant by assisting plant nutrition acquisition, modulating plant hormone levels, inducing accumulation of osmolytes and antioxidants, and up or down regulating the growth-related genes in plants. Though such bacteria have shown the potential to improve plant health, in-depth mechanisms through which microbes confer environmental stress tolerance in plants are poorly understood. Thus, further research, for example the role of bacteria on stress-regulated and -responsive mechanisms in plants, particularly at the transcriptome level, will improve our knowledge on plant-microbe interactions and microbe-driven stress tolerance in plants. Similarly, studies on the role of bacteria in multiple-stress amelioration in plants at field conditions will help to identify suitable bioinoculants to improve crop productivity under adverse environmental conditions. In the present review we elaborate on the interactions among plant, plant-beneficial Pseudomonas spp., and various environmental stresses with an objective to explore the underlying mechanisms involved in microbe-mediated stress tolerance in plants.