Target of Rapamycin (TOR) negatively regulates chlorophyll degradation and lipid peroxidation and controls responses under abiotic stress in Arabidopsis thaliana

The Target of Rapamycin (TOR) is a conserved multifunctional Serine/Threonine protein kinase present in all eukaryotes, which controls several important signaling pathways related to growth and development. In the present investigation, we report that TOR overexpressing Arabidopsis plants ATR-1.4.27, and ATR-3.7.32 exhibit enhanced tolerance to osmotic and salt stress treatments. The TOR overexpressing lines ATR-1.4.27, and ATR-3.7.32 treated with mannitol (100 mM), NaCl (150 mM), sorbitol (200 mM), and PEG (7% w/v), showed improved performance in root growth, fresh weight, and lateral root density. The transgenic lines also exhibited increased proline and chlorophyll contents along with the significant upregulation of stress-responsive genes compared with their corresponding treated and untreated wild-type (WT) controls. More than 90% degradation of chlorophyll-a, chlorophyll b, and total chlorophyll contents was observed in WT plants under each stress treatment, whereas the two transgenic lines had very low degradation ranging from 40% to 50%. Stress treated TOR-OE lines also showed decreased malondialdehyde (MDA) content, and high chlorophyll fluorescence of PhotosystemII (PSII; F-v/F-m ratio) compared with the treated WT control. Taken together, our results show that the constitutive overexpression of TOR enhances salt and osmotic stress tolerance in Arabidopsis thaliana.

Automated summary

The overexpression of TOR in Arabidopsis enhances tolerance to osmotic and salt stress by promoting root growth and lateral root density, as well as increasing proline and chlorophyll contents. The transgenic lines show significant upregulation of stress-responsive genes, lower chlorophyll degradation, and decreased MDA content compared to the wild-type controls under stress treatments.