AINAC4 Transcription Factor From Halophyte Aeluropus lagopoides Mitigates Oxidative Stress by Maintaining ROS Homeostasis in Transgenic Tobacco

NAC proteins are a large family of plant-specific transcription factors which regulate both ABA-dependent and -independent gene expression. These transcription factors participate in biotic and abiotic stress-response through intricate regulation at transcriptional, post-transcriptional and post-translational levels. In the present study, AINAC4 transcription factor was isolated from a salt excreting halophyte Aeluropus lagopoides. The AINAC4 has an open reading frame of 936 bp, encoding a protein of 312 amino acid, with an estimated molecular mass of 34.9 kDa. The AINAC4 showed close homology to monocot NACs in the phylogenetic tree. In silico analysis revealed that AINAC4 possess the characteristic A-E subdomains within the NAC domain. The AINAC4 showed sixteen post-translational phosphorylation sites. The AINAC4 transcript was significantly upregulated with dehydration and H2O2 treatments, showing its role in osmotic and oxidative stress, respectively. The recombinant protein showed binding to mono as well as tandem repeats of NAC recognition sequence (NACRS) of the erd1 promoter. This is the first report mentioning that overexpression of AINAC4 improved oxidative stress tolerance in tobacco transgenics. The transgenics maintained ROS homeostasis during H2O2 treatment. The transgenics showed regulation of stress-responsive genes including CAT SOD, LEA5, PLC3, ERD10B, THT1 and transcription factors like AP2, ZFP during oxidative stress. Key Message: The AINAC4 transcription factor from recretohalophyte Aeluropus showed regulation with abiotic stresses and binding to NACRS elements of erd1 promoter. The AINAC4 tobacco transgenics showed improved growth with oxidative stress.