Bacillus megaterium strain A12 ameliorates salinity stress in tomato plants through multiple mechanisms

Abstract

Plants must cope with the stress conditions to survive. Plant growth promoting rhizobacteria can improve plant growth either directly or indirectly under stress conditions. However, the possible mechanisms remain unclear. Here we report that Bacillus megaterium strain A12 (BMA12) maintains hormonal and redox homeostasis and restores the photosynthetic efficacy of tomato plants through multiple mechanisms to survive under salinity stress conditions. Tomato plants were cocultivated with BMA12 under saline conditions. The application of BMA12 significantly increased plant growth and photosynthetic capacity. BMA12 decreased production of ROS and ethylene but increased expression levels of selected genes responsible for repairing of damaged photosynthetic apparatus and maintenance of redox homeostasis. Furthermore, BMA12 significantly altered metabolic profile to restore perturbations of tomato plant physiology impaired with salinity stress. This study proves that BMA12 can be used in the conventional agriculture system in the salinity effected fields.

Roles of Plant Growth-Promoting Rhizobacteria (PGPR) in Stimulating Salinity Stress Defense in Plants: A Review

“…Likewise, an increase in SL, RL, SFW, RFW, and Tchl was observed in the L. adecarboxylata -inoculated tomato plants with 22%, 16%, 28%, 51%, and 13% higher than those in the control plants, respectively [ 104 ]. The same trend in increased vegetative parameters was found in the studies of Li and Jiang [ 42 ], Khan et al [ 40 ], Sapre et al [ 44 ], Sarkar et al [ 49 ], Akram et al [ 45 ], and Alexander et al [ 48 ]. The increase in Tchl was widely observed in various studies, however, the extent to which these pigments increased depends on PGPR strains, NaCl treatments, and plant species.…”

“…The increased activities of AEs and/or the elevated accumulations of osmoregulators in PGPB-inoculated plants were reported by Li and Jiang [ 42 ], Akram et al [ 45 ], Vaishnav et al [ 47 ], Khalid et al [ 58 ], Kim et al [ 96 ], Habib et al [ 97 ], Kang et al [ 104 ], Zhu et al [ 107 ], Halo et al [ 151 ], Bharti et al [ 152 ], El-Esawi et al [ 153 ], Vimal et al [ 154 ], El-Nahrawy and Yassin [ 155 ], Sun et al [ 156 ]. For instance, the activity of ROS-scavenging enzymes SOD, CAT of Enterobacter -treated okra plants was the highest amongst all treatments, in parallel with their highest vegetative parameters SFW, SDW, RFW, and RDW [ 97 ].…”

“…[ 41 ], maize ( Zea mays L.) [ 42 ], and cucumber ( Cucumis sativus L.) [ 43 ] seedlings, respectively. However, contrary to these studies, the reduced contents of Tchl were tremendously varied from 22% in oat ( Avena sativa ) seedlings [ 44 ], 41–42% in tomato ( Solanum lycopersicum L.) seedlings [ 45 , 46 ], 44% in tomato ( Solanum lycopersicum L.) plants [ 47 ], 50% in peanut ( Arachis hypogaea ) seedlings [ 48 ], 56% in rice ( Oryza sativa L.) seedlings [ 49 ] to 61% in rapeseed ( Brassica napus L.) plants [ 30 ], respectively. In addition, under salt detriment, 16% of Car decreased in the ginseng plantlets, 19% of Car reduced in the mung bean plants, and 49% of Car decreased in the tomato seedings were reported by Sukweenadhi et al (2018) [ 50 ], Shahid et al (2021) [ 36 ], and Akram et al (2019) [ 45 ], respectively.…”

“…The increase in Tchl was widely observed in various studies, however, the extent to which these pigments increased depends on PGPR strains, NaCl treatments, and plant species. For instance, only a 5% Chl increase in maize seedling bacterized with B. aquimaris DY-3 was noticed by Li and Jiang (2017) [ 42 ], whereas a 12% increase in P. putida H-2-3-inoculated soybean seedlings [ 41 ], a 17% increase in S. maltophilia BJ01-peanut seedlings [ 48 ], a 29% increase in K. sacchari -treated mung bean seedlings [ 36 ], a 41% increase in Bacillus megaterium BMA12-bacterized tomato seedlings [ 45 ], 46% in B. pupilus -inoculated rice seedlings [ 40 ], and 60% in A. brasilense -treated white clover plants [ 58 ].…”

Insights Into Microbially Induced Salt Tolerance and Endurance Mechanisms (STEM) in Plants

“…In addition, reduction of ROS levels upregulated expression of the PsbA gene (encodes D1 protein that repairs stress damaged photosystem). Increased cytokinin production diminished the degradation of photosynthetic proteins and elevated the expression levels of genes related to photosystems under stress conditions ( Akram et al, 2019 ).…”