Genome-Wide Identification and Analysis of Phosphate Utilization Related Genes (PURs) Reveal Their Roles Involved in Low Phosphate Responses in Brassica napus L

Abstract Background: Phosphorus (P) is an essential macronutrient for Brassica napus L. growth and development, and is mainly acquired from the soil as phosphate (Pi). However, there is no research on the system analysis of Pi utilization related genes (PURs) in B. napus yet. Results: In this study, 285 PURs were identified in B. napus genome, including 4 transcription factor (TF) families (83 genes) and 17 structural gene families (202 genes). Subcellular localization analysis showed that the proteins encoded by PURs were mainly located in the nucleus (~46.0%) and cell membrane (~36.5%). Chromosome localization analysis suggested that PURs were unequally distributed on the 19 chromosomes of B. napus, and tended to distribute on the Cn-subgenome (An:131, Cn:149). Collinearity analysis revealed that allopolyploidization and small-scale duplication events resulted in the large expansion of PURs. Expression and functional divergence of PURs may initially occur in the promoter region during evolution due to the lower sequence identity in the promoter than in CDS regions. A total of 362 genes were identified as PURs regulators, belonging to 32 TF families and 56 types of miRNAs. Spatiotemporal expression analysis demonstrated that PURs were widely expressed during the whole developmental stages, and most synteny-gene pairs (76.42%) shared conserved expression patterns. RNA-seq analyses revealed that most PURs were induced by LP stress, and the hub genes were generally the Pi transporter (PHT) family members. qRT-PCR analysis proved that the expression levels of four PURs were positively correlated with the root system architecture of three B. napus varieties under LP supply at the seedling stage. Conclusion: The 285 PURs were identified from B. napus with strong LP inducible expression profile. Our findings regarding the evolution, transcriptional regulation, and expression of PURs provide valuable information for further functional research.