The Comparision Of HtNHXl And HtNHX2 On Rice Salt Tolerance And Nutrition Absorbing Efficiency

Soil salinity is one of the major obstacles in modern agricultural activity.Plant salt toxicity is mainly caused by Na~+ and Cl-while Na~+ overtaking is the primary cause.In plant cell.the K+ concentration is around 80-150mM,it is important for tugor regulation.K+ is also important for plant salt resistance,which antagonists Na~+ accumulation.Maintaining high K+ low Na~+,particular in the shoot,is a common stragety for plant growth and survival in high salt condition.Different plants display different salt sensitivity,for example,rice is barely tolerant to salt while barley is a one on the contrary.Taking the good advantage of modern molecular biology techniques to improve rice salt tolerance is an important approach for breeding salt tolerance rice.Previously we have cloned two full-length Na~+/H~+ antiporters HtNHXl and HtNHX2 from Helianthus tuberosus which are located in the cell,and have expressed these two genes in rice Nipponbare cultivar,respectively.In this study,we have isolated five lines of each gene expressing rice with one copy of gene inserted from the pools of HtNHX1 or HtNHX2 expressing rice plants.We compared side by side of these two genes on enhancing rice salt tolerance,improving rice K+ uptake efficiency and elevating rice nutrients uptake efficiency in both liquid and solid culture conditions.The results are summarized as following:1.In normal potassium supply condition,the expression of HtNHX1 or HtNHX1 has no effect on rice growth,but both genes improve rice biomass accumulation at salt stress condition,and in similar extension.2.At low potassium,with or without additional salt stress condition,HtNHX2 enhances rice biomass accumulation;however,HtNHX1 improves rice growth only when additional salt was included.3.HtNHX2,but not HtNHX1 enhances rice nutrients uptake efficiency.At low nutrients supply level,the growth and yield of HtNHX2 transgenic rice plants are much better than WT,while the yield of HtNHXl transgenic rice is even worse than WT at the same condition.By comparing their N?P?K contents,we found that HtNHX2 transgenic rice accumulated much more N?P?K compared to WT and HtNHX1 expressing rice lines.Taking together,both HtNHX1 and HtNHX2 can enhance rice salt tolerance but in different mechanisms.HtNHX1 enhances rice salt tolarance by keeping high K+/Na~+ ratio and requiring high K+ administration,while HtNHX2 enhances rice not only salt tolerance but also globally nutrients uptake efficiency.