Abstract
Potassium (K+) levels in the soil often limit plant growth and development. As a result, crop production largely relies on the heavy use of chemical fertilizers, presenting a challenging problem in sustainable agriculture. To breed crops with higher K+-use efficiency (KUE), we must learn how K+ is acquired from the soil by the root system and transported to the rest of the plant through K+ transporters. In this study, we identified the function of the rice K+ transporter OsHAK8, whose expression level is downregulated in response to low-K+ stress. When OsHAK8 was disrupted by CRISPR/Cas9-mediated mutagenesis, Oshak8 mutant plants showed stunted growth, especially under low-K+ conditions. Ion content analyses indicated that K+ uptake and root-to-shoot K+ transport were significantly impaired in Oshak8 mutants under low-K+ conditions. As the OsHAK8 gene was broadly expressed in different cell types in the roots and its protein was targeted to the plasma membrane, we propose that OsHAK8 serves as a major transporter for both uptake and root-to-shoot translocation in rice plants.
Highlights
Potassium (K+) is an essential macronutrient for plant growth and development
We identified the function of the rice K+ transporter OsHAK8, whose expression level is downregulated in response to low-K+ stress
Under low-K+ conditions, AtAKT1 is activated in plant root hair by a regulatory pathway, which entails calcineurin B-like calcium sensors (CBL1 and CBL9) functioning together with their interacting kinase (CIPK23) (Li et al, 2006; Xu et al, 2006; Cheong et al, 2007; Luan, 2009; Luan et al, 2009)
Summary
Potassium (K+) is an essential macronutrient for plant growth and development. sufficient K+ supplies are necessary to promote crop growth and development (Clarkson and Hanson, 1980; Leigh and Wyn Jones, 1984). Many channels and carriers involved in K+ absorption and translocation have been identified and their functions characterized in the model plant Arabidopsis (Adams and Shin, 2014; Luan et al, 2017; Tang et al, 2020). OsAKT1 and OsHAK5, like AtAKT1 and AtHAK5, mediate K+ uptake in rice roots (Li et al, 2014; Yang et al, 2014), K+ channels such as OsKATs and OsAKTs may be involved in K+ accumulation in the cytoplasm in response to salt stress (Musavizadeh et al, 2021). We showed that OsHAK8 plays crucial role in K+ uptake and K+ translocation from root to shoot, especially under low-K+ conditions
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