Overexpression of AlNAC1 from recretohalophyte Aeluropus lagopoides alleviates drought stress in transgenic tobacco

Abstract

Abstract Drought greatly limits agricultural yield worldwide. The NAC transcription factors play important role during plant growth, development and ABA dependent/independent stress regulation. The AlNAC1 from Aeluropus lagopoides (Poaceace, halophyte) encodes 375 amino acids and gets clustered with NAC TFs from monocots. In-silico analysis showed that it contains bipartite nuclear localization sequence within the conserved NAC domain, post-translational modification sites and belongs to NAM sub-family. The recombinant AlNAC1 protein binds to NACRS cis-element of erd1 promoter. The overexpression of AlNAC1 in transgenic tobacco enhanced drought tolerance, which can be attributed to increased photosynthetic pigments, membrane stability, osmoprotectants, antioxidative enzyme activity and reduced accumulation of reactive oxygen species. Also, AlNAC1 transgenics showed improved water use efficiency, electron transport rate and chlorophyll fluorescence related photosynthetic parameters (Fv/Fm, photochemical and non-photochemical quenching and ФPSII) during drought. Interestingly, AlNAC1 transgenics showed increased number of closed stomata during drought that can be correlated to the enhanced endogenous abscisic acid (ABA), indicating ABA-regulated stomatal movement in transgenics. Furthermore, expression of stress-responsive (P5CS, LTP1 and CAT) and photosynthesis-related (Rca1 and Cab40) genes were upregulated. Thus, the present study suggest that AlNAC1 might work in an ABA-dependent manner to alleviate drought stress by regulating stomatal movement, photosynthesis and reduce oxidative damage in transgenics.