Drought-Stress Tolerance in Wheat Seedlings Conferred by Phenazine-Producing Rhizobacteria

• Published in: Frontiers in microbiology 2019-07, Vol.10, p.1590-1590
• Main Authors: Mahmoudi, Tessa Rose, Yu, Jun Myoung, Liu, Shuyu, Pierson, 3rd, Leland S, Pierson, Elizabeth A
• Format: Article
• Language: English
• Subjects: BASIC BIOLOGICAL SCIENCES; drought-stress tolerance; Microbiology; phenazine; plant-microbe interactions; Pseudomonas; wheat
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2019.01590

The specific role of phenazines produced by rhizosphere-colonizing in mediating wheat seedling drought-stress tolerance and recovery from water deficit was investigated using 30-84 and isogenic derivatives deficient or enhanced in phenazine production compared to wild type. Following a 7-day water deficit, seedlings that received no-inoculum or were colonized by the phenazine mutant wilted to collapse, whereas seedlings colonized by phenazine producers displayed less severe symptoms. After a 7-day recovery period, survival of seedlings colonized by phenazine-producing strains exceeded 80%, but was less than 60% for no-inoculum controls. A second 7-day water deficit reduced overall survival rates to less than 10% for no-inoculum control seedlings, whereas survival was ∼50% for seedlings colonized by phenazine-producers. The relative water content of seedlings colonized by phenazine-producers was 10-20% greater than for the no-inoculum controls at every stage of water deficit and recovery, resulting in higher recovery indices than observed for the no-inoculum controls. For 10-day water deficits causing the collapse of all seedlings, survival rates remained high for plants colonized by phenazine-producers, especially the enhanced phenazine producer (∼74%), relative to the no-inoculum control (∼25%). These observations indicate that seedlings colonized by the phenazine-producing strains suffered less from dehydration during water deficit and recovered better, potentially contributing to better resilience from a second drought/recovery cycle. Seedlings colonized by phenazine-producing strains invested more in root systems and produced 1.5 to 2 fold more root tips than seedlings colonized by the phenazine mutant or the no-inoculum controls when grown with or without water deficit. The results suggest that the presence of phenazine-producing bacteria in the rhizosphere provides wheat seedlings with a longer adjustment period resulting in greater drought-stress avoidance and resilience.