Habitat-adapted heterologous symbiont Salinispora arenicola promotes growth and alleviates salt stress in tomato crop plants

Abstract

To ensure food security given the current scenario of climate change and the accompanying ecological repercussions, it is essential to search for new technologies and tools for agricultural production. Microorganism-based biostimulants are recognized as sustainable alternatives to traditional agrochemicals to enhance and protect agricultural production. Marine actinobacteria are a well-known source of novel compounds for biotechnological uses. In addition, former studies have suggested that coral symbiont actinobacteria may support co-symbiotic photosynthetic growth and tolerance and increase the probability of corals surviving abiotic stress. We have previously shown that this activity may also hold in terrestrial plants, at least for the actinobacteria Salinispora arenicola during induced heterologous symbiosis with a wild Solanaceae plant Nicotiana attenuata under in vitro conditions. Here, we further explore the heterologous symbiotic association, germination, growth promotion, and stress relieving activity of S. arenicola in tomato plants under agricultural conditions and dig into the possible associated mechanisms. Tomato plants were grown under normal and saline conditions, and germination, bacteria-root system interactions, plant growth, photosynthetic performance, and the expression of salt stress response genes were analyzed. We found an endophytic interaction between S. arenicola and tomato plants, which promotes germination and shoot and root growth under saline or non-saline conditions. Accordingly, photosynthetic and respective photoprotective performance was enhanced in line with the induced increase in photosynthetic pigments. This was further supported by the overexpression of thermal energy dissipation, which fine-tunes energy use efficiency and may prevent the formation of reactive oxygen species in the chloroplast. Furthermore, gene expression analyses suggested that a selective transport channel gene, SlHKT1,2, induced by S. arenicola may assist in relieving salt stress in tomato plants. The fine regulation of photosynthetic and photoprotective responses, as well as the inhibition of the formation of ROS molecules, seems to be related to the induced down-regulation of other salt stress response genes, such as SlDR1A-related genes or SlAOX1b. Our results demonstrate that the marine microbial symbiont S. arenicola establishes heterologous symbiosis in crop plants, promotes growth, and confers saline stress tolerance. Thus, these results open opportunities to further explore the vast array of marine microbes to enhance crop tolerance and food production under the current climate change scenario.

Application of Seaweed Generates Changes in the Substrate and Stimulates the Growth of Tomato Plants

“…The macronutrient (N, P, K, S, Mg, Ca, and Na) and micronutrient (Zn, Fe, Mn, and Cu) content were determined by the same method described in Section 3.1 . In addition, to corroborate that the salt contained in the algae powder did not affect the plants growth, the SlHB7 gene expression related to the response to salinity stress in tomato was performed according to the procedure described by Becerril–Espinosa et al [ 92 ].…”

Dry Stamping Coral Powder: An Effective Method for Isolating Coral Symbiotic Actinobacteria

“…For example, after learning that actinobacteria share a niche with a photosynthetic coral symbiont [4], we evaluated whether applying Salinispora arenicola, a symbiotic actinobacterium present in corals, would benefit the growth of terrestrial plants. We found that S. arenicola promoted the growth of tomato and wild tobacco plants while protecting them from salinity stress, highlighting its biotechnological potential for agricultural production [18,19]. In addition, the ability of actinobacteria to produce antibiotics is well known, with these organisms currently producing 45% of commercial antibiotics [20].…”

“…Coral samples of healthy adult colonies of Porites lobata (PL), Porites panamensis (PP), and Pavona gigantea (PG) were collected from several tropical coral ecosystems in the central Mexican Pacific (19 C and transported to the laboratory. Once in the laboratory, the seawater and mucus secretions on the surface of the coral samples were removed.…”

“…The isolation of new actinobacteria species and strains expands our understanding of actinobacteria diversity, their functions within corals, and their biotechnological potential. For example, our laboratory group has successfully isolated, via dry stamping, a Salinispora strain that shows notable plant growth-promoting ability when applied to tomato and wild tobacco seedlings [18,19]. These findings highlight the necessity of standardized methodologies for isolating actinobacteria from corals in order to understand ecological activities in marine ecosystems and prospective biotechnological applications (in this case, agriculture production).…”