The intracellular potassium (K+) homeostasis, which is crucial for plant survival in saline environments, is modulated by K+ channels and transporters. Some members of the high‐affinity K+ transporter (HAK) family are believed to function in the regulation of plant salt tolerance, but the physiological mechanisms remain unclear. Here, we report a significant inducement of OsHAK21 expression by high‐salinity treatment and provide genetic evidence of the involvement of OsHAK21 in rice salt tolerance. Disruption of OsHAK21 rendered plants sensitive to salt stress. Compared with the wild type, oshak21 accumulated less K+ and considerably more Na+ in both shoots and roots, and had a significantly lower K+ net uptake rate but higher Na+ uptake rate. Our analyses of subcellular localizations and expression patterns showed that OsHAK21 was localized in the plasma membrane and expressed in xylem parenchyma and individual endodermal cells (putative passage cells). Further functional characterizations of OsHAK21 in K+ uptake‐deficient yeast and Arabidopsis revealed that OsHAK21 possesses K+ transporter activity. These results demonstrate that OsHAK21 may mediate K+ absorption by the plasma membrane and play crucial roles in the maintenance of the Na+/K+ homeostasis in rice under salt stress.
細(xì)胞內(nèi)的鉀離子（K+）穩(wěn)態(tài)對植物在鹽堿環(huán)境下的存活是十分重要的，受到K+通道和轉(zhuǎn)運蛋白控制。一些高親和性K+轉(zhuǎn)運蛋白（HAK）家族成員被認(rèn)為在調(diào)控植物抗鹽性中發(fā)揮功能，但是生理機(jī)理仍不清楚。本文我們報道了OsHAK21受到高鹽處理的強(qiáng)烈誘導(dǎo)，并提供了OsHAK21參與水稻耐鹽脅迫的遺傳證據(jù)。破壞OsHAK21會導(dǎo)致植株對鹽脅迫敏感。與野生型相比，oshak21在莖部和根部均積累更少K+而積累相當(dāng)多的Na+，并且K+吸收速率顯著降低，而Na+吸收速率則加快。我們對亞細(xì)胞定位以及表達(dá)模式的分析表明，OsHAK21定位在細(xì)胞膜上，在木質(zhì)部薄壁組織和個體內(nèi)皮層細(xì)胞（推測為通道細(xì)胞）表達(dá)。OsHAK21在K+缺陷的酵母和擬南芥中的進(jìn)一步功能分析表明，OsHAK21具有K+轉(zhuǎn)運活性。這些結(jié)果表明，OsHAK21可能通過細(xì)胞膜介導(dǎo)K+吸收，并且在維持鹽脅迫條件下水稻體內(nèi)Na+/K+穩(wěn)態(tài)中發(fā)揮重要作用。