Bacillus licheniformis SA03 Confers Increased Saline–Alkaline Tolerance in Chrysanthemum Plants by Induction of Abscisic Acid Accumulation

Abstract

Soil saline-alkalization is a major abiotic stress that leads to low iron (Fe) availability and high toxicity of sodium ions (Na+) for plants. It has recently been shown that plant growth promoting rhizobacteria (PGPR) can enhance the ability of plants to tolerate multiple abiotic stresses such as drought, salinity, and nutrient deficiency. However, the possible involvement of PGPR in improving saline–alkaline tolerance of plants and the underlying mechanisms remain largely unknown. In this study, we investigated the effects of Bacillus licheniformis (strain SA03) on the growth of Chrysanthemum plants under saline–alkaline conditions. Our results revealed that inoculation with SA03 alleviated saline–alkaline stress in plants with increased survival rates, photosynthesis and biomass. The inoculated plants accumulated more Fe and lower Na+ concentrations under saline–alkaline stress compared with the non-inoculated plants. RNA-Sequencing analyses further revealed that SA03 significantly activated abiotic stress- and Fe acquisition-related pathways in the stress-treated plants. However, SA03 failed to increase saline–alkaline tolerance in plants when cellular abscisic acid (ABA) and nitric oxide (NO) synthesis were inhibited by treatment with fluridone (FLU) and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO), respectively. Importantly, we also found that NO acted downstream of SA03-induced ABA to activate a series of adaptive responses in host plants under saline–alkaline stress. These findings demonstrated the potential roles of B. licheniformis SA03 in enhancing saline–alkaline tolerance of plants and highlighted the intricate integration of microbial signaling in regulating cellular Fe and Na+ accumulation.

Bacillus licheniformis FMCH001 Increases Water Use Efficiency via Growth Stimulation in Both Normal and Drought Conditions

“…Hence, FMCH001 inoculated plants offered advantages over uninoculated control plants in regulating the level of ROS in plant cells. Similarly, Zhou et al (2017) reported enhanced activity of SOD, CAT, APX, and GPX in Chrysanthemum inoculated with B. licheniformis SA03 under saline-alkaline conditions. In addition, very recently Chiappero et al (2019) also reported similar findings, i.e., higher antioxidant capacity in inoculated plants in relation to uninoculated controls under drought stress.…”

Defining plant growth promoting rhizobacteria molecular and biochemical networks in beneficial plant-microbe interactions

“…Many studies have observed increased ABA accumulation in PGPR-inoculated plants under various abiotic stress conditions. Bacillus licheniformis SA03-treated Chrysanthemum morifolium in saline-alkaline conditions had nearly double the level of ABA in leaves than the control as detected by ELISA (Zhou et al 2017). Plants inoculated with SA03 and exposed to saline-alkaline stress conditions showed fewer symptoms and had higher fresh and dry shoot weights, whereas inoculated plants treated with the ABA inhibitor FLU exhibited no tolerance to the stress.…”

Salt-Tolerant Plant Growth Promoting Rhizobacteria for Enhancing Crop Productivity of Saline Soils

“…Most of the isolates also showed their potential in improving salt tolerance, growth, and yield of rice under salt-stress conditions. ST-PGPR strain Bacillus licheniformis SA03 isolated from Chrysanthemum plants grown in saline-alkaline soil of China conferred increased salt tolerance in Chrysanthemum (Zhou et al, 2017).…”