An endoplasmic reticulum–localized cytochrome b ₅ regulates high-affinity K ⁺ transport in response to salt stress in rice

Abstract

Potassium (K+) is an essential element for growth and development in both animals and plants, while high levels of environmental sodium (Na+) represent a threat to most plants. The uptake of K+ from high-saline environments is an essential mechanism to maintain intracellular K+/Na+ homeostasis, which can help reduce toxicity caused by Na+ accumulation, thereby improving the salt tolerance of plants. However, the mechanisms and regulation of K+-uptake during salt stress remain poorly understood. In this study, we identified an endoplasmic reticulum–localized cytochrome b5 (OsCYB5-2) that interacted with a high-affinity K+ transporter (OsHAK21) at the plasma membrane. The association of OsCYB5-2 with the OsHAK21 transporter caused an increase in transporter activity by enhancing the apparent affinity for K+-binding but not Na+-binding. Heme binding to OsCYB5-2 was essential for the regulation of OsHAK21. High salinity directly triggered the OsHAK21–OsCYB5-2 interaction, promoting OsHAK21-mediated K+-uptake and restricting Na+ entry into cells; this maintained intracellular K+/Na+ homeostasis in rice cells. Finally, overexpression of OsCYB5-2 increased OsHAK21-mediated K+ transport and improved salt tolerance in rice seedlings. This study revealed a posttranslational regulatory mechanism for HAK transporter activity mediated by a cytochrome b5 and highlighted the coordinated action of two proteins to perceive Na+ in response to salt stress.

Integrated analysis of transcriptome and metabolome reveals molecular mechanisms of salt tolerance in seedlings of upland rice landrace 17SM-19

“…The predominant toxic ion is Na + because it inhibits K + absorption, and thus, maintaining a high K + /Na + ratio is important to improve salt tolerance in glycophytic plants (Hauser and Horie, 2010 ; Ismail and Horie, 2017 ). Increasing K + uptake and decreasing K + efflux are two major strategies to retain K + in glycophytic plants under salt stress (Hauser and Horie, 2010 ; Song et al, 2021 ). In this study, SKC and SDW were correlated.…”

Sequence Characteristics and Expression Analysis of GhCIPK23 Gene in Upland Cotton (Gossypium hirsutum L.)

“…The downregulated expression of GhCIPK23 might participate in reducing Na + accumulation and balancing K + /Na + homeostasis under salt stress in upland cotton. Recent research shows that potassium signaling has been shown to act as a key determinant of plant salinity tolerance [ 40 , 41 , 42 , 43 ]. However, it is unclear whether GhCIPK23 may also be involved in K + uptake by plant roots under high sodium conditions, and the function of GhCIPK23 in regulating Na + and K + homeostasis needs to be addressed in future research.…”

A 14‐3‐3 protein positively regulates rice salt tolerance by stabilizing phospholipase C1

“…The CDS of OsGF14b and OsPLC1 were respectively cloned to pCAMBIA1300‐cLUC and pCAMBIA1300‐nLUC using primers OsGF14b‐cLUC‐F/R and OsPLC1‐nLUC‐F/R (Table ). LCI analyses were performed as described previously (Chen et al, 2008; Han et al, 2015; Song et al, 2021). In brief, tobacco leaves were agroinfiltrated by the GV3101 containing different combinations, including OsGF14b ‐cLUC/ OsPLC1 ‐nLUC, OsGF14b ‐cLUC/nLUC, cLUC/ OsPLC1 ‐nLUC, or nLUC/cLUC.…”