Genome-wide mining of respiratory burst homologs and its expression in response to biotic and abiotic stresses in Triticum aestivum.

BACKGROUND: Membrane-bound NADPH oxidases (Nicotinamide adenine ainucleotide phosphate oxidase) also called respiratory burst oxidase homologs (Rboh) play an essential role in ROS production under normal as well as environmental stress conditions in plants. OBJECTIVE: To identify and study respiratory burst homologs (Rboh) from the wheat genome as well as characterize their role in various biological and molecular processes along with expression in response to biotic and abiotic stresses. METHODS: The Rboh homologs in the wheat genome were predicted based on data processing, alignment of sequences and phylogenetic analysis of sequences in numerous plant species and wheat. The conserved motifs were known followed by domain design study. The 3-D structure prediction and similarity modeling were administered for NADPH enzyme domain. Gene ontology and a functional study were done in addition to expression analysis of Triticum aestivum respiratory burst oxidase (TaRboh) gene family in response to biotic as well as abiotic stress. RESULTS: Phylogenetic analysis of Rboh gene family members among seven plant species including wheat, classified the family into four subfamilies. Rboh genes are mainly involved in various biological processes such as Response to oxidative stress, Superoxide anion generation, Hydrogen peroxide biosynthetic process. Among the molecular functions, calcium ion binding, peroxidase activity, oxidoreductase activity, superoxide-generating NADPH oxidase activity are essential. Enzyme annotation of the family and superfamily revealed that it encodes to five structural clusters and coding to enzymes NAD(P)H oxidase (H2O2-forming) (EC:1.6.3.1), Ferric-chelate reductase (NADH) (EC: 1.16.1.7), Peroxidase (EC: 1.11.1.7), Ribose-phosphate diphosphokinase (EC: 2.7.6.1). The enzymes contain six membrane-spanning domains, two hemes, and conserved motifs associated with NADPH, EF-hand and FAD binding. The outcomes additionally reflect a distinct role of this enzyme in different molecular functions which are responsible for the stress signaling. Further, the transcripts of TaRboh found expressed in various plant parts such as stem, leaves, spike, seed, and roots. We also observed expression of these gene family members under drought/combination of drought + heat and important wheat pathogens such as Puccinia striformis, Blumeria graminis f.sp. tritici, Fusarium graminiarum, F. pseudograminiarum, and Zymoseptoria tritici. CONCLUSIONS: The investigation demonstrated that identified respiratory burst homologs (Rboh) in T. aestivum were involved in pathogen activated ROS production and have regulatory functions in cell death and defense responses.