Effects of ACC deaminase containing rhizobacteria on plant growth and expression of Toc GTPases in tomato (Solanum lycopersicum) under salt stress

The bacterial enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase plays a key role in lowering plant stress ethylene levels, thereby stimulating plant growth. The present study aims to evaluate whether the ACC deaminase producing plant growth promoting rhizobacterium (PGPR) Pseudomonas putida UW4 can maintain and promote plant growth in saline environments and modulate the expression of chloroplast import apparatus genes in salt-treated tomato plants (Solanum lycopersicum L.). Tomatoes were grown in the presence and absence of the PGPR and shoot length, fresh and dry mass, and chlorophyll concentration were measured after 6 weeks. The expression levels of the Toc GTPases of the chloroplast protein import apparatus were measured using quantitative real-time PCR. The results showed that the rhizobacteria significantly increased shoot length, shoot fresh and dry mass, and the chlorophyll concentration of tomato seedlings grown in the presence of up to 90 mmol.L-1 NaCl. Analysis showed that the expression of most of the Toc GTPase genes was upregulated in tomato seedlings after 6 weeks of exposure to NaCl, which may help facilitate the import into chloroplasts of proteins that are involved in the stress response.