Investigation of PIC1 (permease in chloroplasts 1) gene's role in iron homeostasis: bioinformatics and expression analyses in tomato and sorghum

Iron (Fe) is a crucial micronutrient in plant metabolism; thus, iron homeostasis is critical for plant development. Permease in chloroplast 1 (PIC1) is the first protein determined in the chloroplast playing a role iron homeostasis. In the present study, the PIC1 gene was investigated at a genome-wide scale in four plant genomes; Arabidopsis, tomato, maize and sorghum. Based on the gene ontology database, 21 GO terms were found related to the PIC1 gene, most of which were involved in iron hemostasis and transport. The digital expression data revealed that the expression of the majority of PIC1 genes (62.5%) in Arabidopsis decreased under abiotic stress conditions. Expression profiles of tomato PIC1 (SlPIC1) and sorghum PIC1 (SbPIC1) genes were also analyzed under salt and drought stress conditions using Real Time-quantitative PCR (RT-qPCR). Our wet-lab studies demonstrated that the SbPIC1 gene was down-regulated under salt and drought stresses in all tissues, while SlPIC1 was up-regulated in all but root tissue under drought stress. Some structural variations were detected in predicted 3D structures of PIC1 proteins and the structural similarity values varied between 0.23 and 0.35. Consequently, these results may contribute to the understanding of the PIC1 gene in iron transport and homeostasis in plants.