Identification and characterization of rice ortholog of ferric chelate reductase (FRO2) gene in little millet (Panicum sumatrense Roth ex Roem. & Shult.)

In this study, a rice ortholog of ferric chelate reductase (FRO2) gene, involved in plant metal uptake phenomenon, has been identified and characterized in high iron containing small millet. The work has been accomplished in little millet (Panicum swnatrense Roth ex Roem. & Shutt.) using PCR based amplification and next generation sequencing technology. The genotype RLM-37 was used to amplify FRO2 gene, followed by its sequencing on Ion Torrent's sequencing technology. Gene specific primers designed from rice genome, to amplify full-length gene fragment of 2.8 Kb in rice, generated an amplicon of 2.7 Kb in RLM-37 and its sequencing generated a sequence of 2691 bp. The sequenced amplicon showed high-level sequence similarity with OsFRO2 gene at nucleotide level, whereas low-level sequence homology and structural similarity was observed at protein level in the database. The predicted structure of the gene showed the presence of 6 exons and 5 introns in the little millet gene. The predicted protein sequence domain search showed the presence of ferric reductase domain and NOX_Duar_Like_FAD_NADP domain. The NOX_Duox_Like_FAD_NADP domain is unique to this protein, covering 36% of the millet protein. The 3D structure of this domain was elucidated by homology modelling method and the catalytic domain part was characterized. Thus, the study provides the start point for gene discovery in underexplored millet crops for improving grain nutritive traits.