Functional characterization on the wheat potassium channel gene TaPC1 in mediating plant adaptation to potassium deprivation

Objectives Potassium channel (PC) proteins mediate the transportation of potassium ion (K⁺) across the cellular membranes and play critical roles in improving plant uptake and utilization of potassium under the potassium starvation stress. In this study, we characterized the molecular characterization, expression patterns and function of TaPC1, a differentially expressed gene under low-K stress identified by our previous RNAseq analysis.

Methods Using bioinformatic tools analyzed the molecular property of TaPC1. Adopting hydroponic culture solutions supplemented with sufficient K (6 mmol/L K₂O) and deficient K (0.06 mmol/L K₂O) grew the plants of wheat and transgenic lines. Utilizing DNA recombinant approach constructed the expression plasmids for subcellular location and overexpression of TaPC1. Using genetic transformation approach mediated by Agobacterium tumefaciens transforms leaf discs of tobacco. Adopting conventional phenotypic, physiological and qPCR methods studied the plant growth traits, physiological traits and gene expression patterns.

Results TaPC1 shared high similarities to its plant homologous genes. The protein translated by TaPC1 possessed the conserved transmembrane domains shared by PC proteins and targets to cytoplasm membrane after endoplasmic reticulum (ER) sorted. Under K-deficient treatment, the expression of TaPC1 was upregulated in both roots and leaves. Moreover, its induced transcripts in above tissues were gradually reduced following the sufficient-K recovery treatment (6 mmol/L K₂O), suggesting that it responds to the modified external K levels at transcriptional level. Compared with wild type (WT), the tobacco lines with TaPC1 overexpression were shown to be improved on plant biomass production and cellular antioxidant enzymatic (SOD, CAT and POD) activities and reduced on malondialdehyde (MDA) contents. Expression analysis on the genes encoding antioxidant enzymes revealed that a suite of them, including, NtSOD1, NtCAT1;1, NtPOD1;2 and NtPOD1;6, were upregulated on transcripts in the K-deprived transgenic lines with respect to the WT plants challenged by K deprivation, which suggested the involvement of these genes in mediating reactive oxygen species homeostasis in the K-deficient plants. In addition, the transgenic lines displayed much more accumulated potassium in plants and more improved photosynthetic function than WT under K-deficient treatment.

Conclusions Our investigation indicated that TaPC1 is K starvation-response in expression, whose overexpression confers plants improved K accumulation and cellular ROS homeostasis. Thus, TaPC1 plays critical roles in positively regulating the biomass production and mediating the low-K tolerance of plants.