Perfluorooctanesulfonic Acid Alters the Plant's Phosphate Transport Gene Network and Exhibits Antagonistic Effects on the Phosphate Uptake.

Per- and polyfluoroalkyl substances (PFASs), with significant health risks to humans and wildlife, bioaccumulate in plants. However, the mechanisms underlying plant uptake remain poorly understood. This study deployed transcriptomic analysis coupled with genetic and physiological studies using Arabidopsis to investigate how plants respond to perfluorooctanesulfonic acid (PFOS), a long-chain PFAS. We observed increased expressions of genes involved in plant uptake and transport of phosphorus, an essential plant nutrient, suggesting intertwined uptake and transport processes of phosphorus and PFOS. Furthermore, PFOS-altered response differed from the phosphorus deficiency response, disrupting phosphorus metabolism to increase phosphate transporter (PHT) transcript. Interestingly, pht1;2 and pht1;8 mutants showed reduced sensitivity to PFOS compared to that of the wild type, implying an important role of phosphate transporters in PFOS sensing. Furthermore, PFOS accumulated less in the shoots of the pht1;8 mutant, indicating the involvement of PHT1;8 protein in translocating PFOS from roots to shoots. Supplementing phosphate improved plant's tolerance to PFOS and reduced PFOS uptake, suggesting that manipulating the phosphate source in PFOS-contaminated soils may be a promising strategy for minimizing PFOS uptake by edible crops or promoting PFOS uptake during phytoremediation. This study highlighted the critical role of phosphate sensing and transport system in the uptake and translocation of PFOS in plants.

Functional diversity of Medicago truncatula RNA polymerase II CTD phosphatase isoforms produced in the Arabidopsis thaliana superexpression platform.

Medicago truncatula is a model system for legume plants, which has substantially expanded the genome relative to the prototypical model dicot plant, Arabidopsis thaliana. An essential transcriptional regulator, FCP1 (transcription factor IIF-interacting RNA polymerase II carboxyl-terminal phosphatase 1) ortholog, is encoded by a single essential gene CPL4 (CTD-phosphatase-like 4), whereas M. truncatula genome contains four genes homologous to FCP1/AtCPL4, and splicing variants of MtCPL4 are observed. Functional diversification of MtCPL4 family proteins was analyzed using recombinant proteins (MtCPL4a1, MtCPL4a2, and MtCPL4b) produced in Arabidopsis cell culture system developed for plant protein overexpression. In vitro CTD phosphatase assay using highly purified MtCPL4 preparations revealed a potent CTD phosphatase activity in MtCPL4b, but not two splicing variants of MtCPL4a. On the other hand, in planta binding assay to RNA polymerase II (pol II) revealed a greater pol II-binding activity of both MtCPL4a variants. Our results indicate functional diversification of MtCPL4 isoforms and suggest the presence of a large number of functionally specialized CTD-phosphatase-like proteins in plants.