A high-affinity potassium transporter (MeHKT1) from cassava (Manihot esculenta) negatively regulates the response of transgenic Arabidopsis to salt stress.

BACKGROUND: High-affinity potassium transporters (HKTs) are crucial in facilitating potassium uptake by plants. Many types of HKTs confer salt tolerance to plants through regulating K+ and Na+ homeostasis under salinity stress. However, their specific functions in cassava (Manihot esculenta) remain unclear. RESULTS: Herein, an HKT gene (MeHKT1) was cloned from cassava, and its expression is triggered by exposure to salt stress. The expression of a plasma membrane-bound protein functions as transporter to rescue a low potassium (K+) sensitivity of yeast mutant strain, but the complementation of MeHKT1 is inhibited by NaCl treatment. Under low K+ stress, transgenic Arabidopsis with MeHKT1 exhibits improved growth due to increasing shoot K+ content. In contrast, transgenic Arabidopsis accumulates more Na+ under salt stress than wild-type (WT) plants. Nevertheless, the differences in K+ content between transgenic and WT plants are not significant. Additionally, Arabidopsis expressing MeHKT1 displayed a stronger salt-sensitive phenotype. CONCLUSION: These results suggest that under low K+ condition, MeHKT1 functions as a potassium transporter. In contrast, MeHKT1 mainly transports Na+ into cells under salt stress condition and negatively regulates the response of transgenic Arabidopsis to salt stress. Our results provide a reference for further research on the function of MeHKT1, and provide a basis for further application of MeHKT1 in cassava by molecular biological means.

Positive Regulatory Roles of Manihot esculenta HAK5 under K+ Deficiency or High Salt Stress.

HAK/KUP/KT family members have been identified as playing key roles in K+ uptake and salt tolerance in numerous higher plants. However, their functions in cassava (Manihot esculenta Cantz) remain unknown. In this study, a gene encoding for a high-affinity potassium transporter (MeHAK5) was isolated from cassava and its function was investigated. Subcellular localization analysis showed that MeHAK5 is a plasma membrane-localized transporter. RT-PCR and RT-qPCR indicated that MeHAK5 is predominantly expressed in cassava roots, where it is upregulated by low potassium or high salt; in particular, its highest expression levels separately increased by 2.2 and 2.9 times after 50 µM KCl and 150 mM NaCl treatments. When heterologously expressed in yeast, MeHAK5 mediated K+ uptake within the cells of the yeast strain CY162 and rescued the salt-sensitive phenotype of AXT3K yeast. MeHAK5 overexpression in transgenic Arabidopsis plants exhibited improved growth and increased shoot K+ content under low potassium conditions. Under salt stress, MeHAK5 transgenic Arabidopsis plants accumulated more K+ in the shoots and roots and had reduced Na+ content in the shoots. As a result, MeHAK5 transgenic Arabidopsis demonstrated a more salt-tolerant phenotype. These results suggest that MeHAK5 functions as a high-affinity K+ transporter under K+ starvation conditions, improving K+/Na+ homeostasis and thereby functioning as a positive regulator of salt stress tolerance in transgenic Arabidopsis. Therefore, MeHAK5 may be a suitable candidate gene for improving K+ utilization efficiency and salt tolerance.

[Distribution of Rh blood group in 51 283 cases of inpatients and voluntary blood donors].

Objective To investigate the distribution characteristics of Rh blood group in 51 283 cases of inpatients and voluntary blood donors. Methods Micro-column gel test was used to detect RhD, RhE, Rhe, RhC, Rhc antigen in 31 818 cases of hospitalized patients and 19 465 cases of voluntary blood donors. Results There were significant differences in Rh blood type distribution between inpatients and voluntary blood donors. The mainly phenotype of Rh blood group in the inpatients were DCCee (41.64%) and DCcEe (36.58%), and Rh blood type in voluntary blood donors were DCCee (41.11%) and DCcEe (37.11%). There were noticeable differences in Rh blood group and ABO phenotype between inpatients and voluntary blood donors. The mainly phenotype of the RhD positive patients were CcEe (36.58%) and CCee (41.64%). However, the mainly phenotype of RhD negative patients were ccee (54.30%) and Ccee (30.86%). Additionally, obvious difference of Rh blood group was seen between patients in haematology department and all patients. The voluntary blood donors from different areas including Hefei, Guangzhou, Nanning and Xi'an showed significant different Rh blood group distribution. On the contrary, no obvious difference of Rh blood group was found between Xianyang and Xi'an. Conclusion The differences of Rh blood group distribution have been found in different populations, departments and areas, which make it extremely important to detect Rh blood group in clinical transfusion.