Characterization of DNA Regulatory Elements of the Highly Abundant Secreted Protein 1 (HASP1) Promoter and Analysis of Transcriptomic Responses Under Phosphate Depletion in the Diatom Phaeodactylum tricornutum
Abstract
Phosphorus (P) is essential for all life. The bioavailability of phosphorus in oceans impacts diatoms like Phaeodactylum tricornutum (P. tricornutum). P. tricornutum is extensively used in transcriptomic studies to understand pathways involved in P-acquisition. However, activation mechanisms and roles of regulatory elements in P-acquisition responses remains unclear. Here, I deleted predicted phosphate regulatory sites in P.tricornutum’s HASP1 promoter to create different HASP1-eGFP constructs. Under P-depletion, two constructs showed increased eGFP secretion. Additionally, a HASP1 knockout strain was grown under different phosphorus sources to determine if HASP1 is a phytase. Cells grown in full phosphorus utilized organic sources of phosphorus and cells grown under P-depletion used inorganic sources. HASP1 knockout cells were also used to understand transcriptional responses under phosphorus depletion using RNAseq. This revealed the loss of HASP1 was not essential to cell survival. Understanding diatom responses under P-starvation will contribute to improving P. tricornutum for synthetic biology applications.