In Silico Dissection of Regulatory Regions of PHT Genes from Saccharum spp. Hybrid and Sorghum bicolor and Expression Analysis of PHT Promoters under Osmotic Stress Conditions in Tobacco

Abstract

Phosphorus (P) is the second-most essential macronutrient required for the growth and development of plants. It is involved in a number of cellular processes that contribute to the plant’s growth and development. This study investigated Saccharum spp. hybrid and Sorghum bicolor promoter regions of Phosphate transporters (PHT), viz., PHT1, PHT2, PHT3, PHT4, and PHO1, through in silico analysis. The transcription start sites (TSS), conserved motifs, and CpG islands were studied using various computational techniques. The distribution of TSSs indicated the highest promoter prediction scores (1.0). MSh2 and MSb4 were recognized as the common promoter motifs for PHT promoters, found in with 85 to 100% percentage of distribution. The CpG analysis revealed that the promoter regions of most PHT genes had low CpG density, indicating a possible tissue-specific expression. The PHT promoters were investigated for the presence of biotic- and abiotic-stress-associated transcription factor binding sites (TFbs) that revealed the presence of binding motifs for major transcription factors (TFs), namely, AP2/ERF, bHLH, bZIP, MYB, NAC, and WRKY. Therefore, the in-silico analysis of the promoter regions helps us to understand the regulation mechanism of phosphate transporter promoters and gene expression under stress management. The 5′ regulatory region of the EaPHT gene was isolated from Erianthus, a wild relative of the genus Saccharum. The promoter construct was prepared and transformed in tobacco wherein the promoter drove the expression of GUS. Analysis of GUS expression in transgenic tobacco revealed enhanced expression of GUS under salt-stress conditions. This is the first report of the isolation and characterization of a phosphate transporter gene promoter from Erianthus and is expected to be useful for the development of salt-stress transgenic crop plants.