SES1 is vital for seedling establishment and post-germination growth under high-potassium stress conditions in Arabidopsis thaliana.

Abstract

The potassium ion (K+) plays an important role in maintaining plant growth and development, while excess potassium in the soil can cause stress to plants. The understanding of the molecular mechanism of plant's response to high KCl stress is still limited. At the seed stage, wild type (WT) and SENSITIVE TO SALT1 (SES1) mutants were exposed to different concentrations of potassium treatments. Tolerance was assayed as we compared their performances under stress using seedling establishment rate and root length. Na+content, K+content, and K+/Na+ ratio were determined using a flame atomic absorption spectrometer. In addition, the expressions of KCl-responding genes and ER stress-related genes were also detected and analyzed using qRT-PCR. SES1 mutants exhibited seedling establishment defects under high potassium concentration conditions and exogenous calcium partially restored the hypersensitivity phenotype of ses1 mutants. The expression of some K+ transporter/channel genes were higher in ses1-2, and the ratio of potassium to sodium (K+/Na+) in ses1-2 roots decreased after KCl treatment compared with WT. Further analysis showed that the ER stress marker genes were dramatically induced by high K+ treatment and much higher expression levels were detected in ses1-2, indicating ses1-2 suffers a more serious ER stress than WT, and ER stress may influence the seedling establishment of ses1-2 under high KCl conditions. These results strongly indicate that SES1 is a potassium tolerance relevant molecule that may be related to maintaining the seedling K+/Na+ balance under high potassium conditions during seedling establishment and post-germination growth. Our results will provide a basis for further studies on the biological roles of SES1 in modulating potassium uptake, transport, and adaptation to stress conditions.