Identification of Halophilic and Halotolerant Bacteria from the Root Soil of the Halophyte Sesuvium verrucosum Raf.

Soil salinity is a condition that limits crop growth and productivity, and soil-dwelling bacteria from halophytic plant roots may be a viable strategy to cope with low productivity due to salt stress. Halophilic and halotolerant bacteria of the root soil of Sesuvium verrucosum were analyzed in this study as there is little evidence regarding its associated microbiology. Soil was sampled from the roots of Sesuvium verrucosum to obtain the cultivable bacteria. Their morphological characteristics were identified and they were molecularly identified by the 16S sequence. The growth capacity of the bacteria was determined at different levels of pH and salinity, and several growth promotion characteristics were identified, such as phosphorus solubilization, indole acetic acid production by the tryptophan-dependent (AIAt) and tryptophan-independent (IAA) pathways, ammonium production from organic sources, solubilization of carbonates, and zinc and sodium capture capacity. In addition, the bacteria that presented the best characteristics for germination variables of Solanum lycopersicum were evaluated. A total of 20 bacteria from root soil of Sesuvium verrucosum Raf. belonging to the phyla Proteobacteria (50%), Firmicutes (45%) and Actinobacteria (5%) were identified, with each one having different morphological characteristics. Among the bacterial isolates, 45% had the ability to resist different levels of salinity and pH, ranging from 0 to 20% of NaCl, and pH between 5 and 11. Moreover, these bacteria had the capacity to solubilize carbonates, phosphorus and zinc, capture sodium, produce ammonium from organic substrates and IAA (indole acetic acid), and promote enzymatic activity of amylases, proteases, lipases and cellulases. The bacteria evaluated on the germination of Solanum lycopersicum had an influence on germination at different salinity levels, with greater influence at 100 mM NaCl. This demonstrated that halophilic bacteria belonging to the rhizosphere of Sesuvium verrucosum have the ability to promote growth in extreme salinity conditions, making them candidates for the recovery of productivity in saline soils.

LEA13 and LEA30 Are Involved in Tolerance to Water Stress and Stomata Density in Arabidopsis thaliana.

Late embryogenesis abundant (LEA) proteins are a large protein family that mainly function in protecting cells from abiotic stress, but these proteins are also involved in regulating plant growth and development. In this study, we performed a functional analysis of LEA13 and LEA30 from Arabidopsis thaliana. The results showed that the expression of both genes increased when plants were subjected to drought-stressed conditions. The insertional lines lea13 and lea30 were identified for each gene, and both had a T-DNA element in the regulatory region, which caused the genes to be downregulated. Moreover, lea13 and lea30 were more sensitive to drought stress due to their higher transpiration and stomatal spacing. Microarray analysis of the lea13 background showed that genes involved in hormone signaling, stomatal development, and abiotic stress responses were misregulated. Our results showed that LEA proteins are involved in drought tolerance and participate in stomatal density.