Reseach On The Salt Tolerance Of Transgenic Arabidopsis Thaliand Into K~+ Channel Gene Mirk And Its Artificial Modified Gene

Soil salinization is a global problem,which seriously affects the growth and development of the plants.Melon（Cucumis melo L.）is an important economic crop in the world,which has the strong salt-tolerance.So it can be a salt tolerant or desalination plant resource.Plants to salt stress response and resistance is extremely complex process.High salt concentration will reduce the water absorption ability of plant root in the soil,so that causing plant wilting and even death.At the same time the root absorption of Na⁺ competing with a variety of nutrition elements,such as,can affect plant absorption and transport of K⁺,and seriously affect the normal growth of the plant.As the main way of absorport and transformation of potassium,K⁺ channel may be related to salt tolerance of plants.MIRK was cloned from muskmelon“Chunli”（Cucumis melon L.）by our previous work and tranfered it Xenopus oocytes.Electrophysiological analysis showed that Na⁺inhibited the effect of MIRK,which might be determined by multiple amino acids like 232-234 serine,lysine and glutamine.To explore the molecular base of blockage site（s）,the segment S5-P-S6 of MIRK was replaced by the same segment of KAT2 which was not inhibited by Na⁺,the artificial modified melon potassium channel gene△KAT2/MIRK was obtained.The electrophysiological results indicated that△KAT2/MIRK still can mediate K⁺ uptake,but the inward current was not suppressed by Na⁺.MIRK and△KAT2/MIRK were transferred into Arabidopsis thaliana（kat1）by Floral Dip method.Resistance testing and PCR results confirmed the p35S::MIRK-kat1 and p35S::△KAT2/MIRK-kat1.In order to study the relationship between MIRK and tolerance in plants,transgenic plants（T₃-generation）were treated with different concentrations of NaCl solution（0、50、100mmol/L）.The phenotype of transgenic plants and chlorophyll content and the ratio of potassium to sodium were measured.Those results indicated that melon K⁺channel gene MIRK transformation could improve plants salt tolerance.Results show that the MIRK kat1 arabidopsis in the expression can mediate K⁺ internal flow.And we speculated that the blockage of MIRK currents by external Na⁺,which is channel outer segments（S5-P-S6）,an important role on the plant senescence,and may participate in the corresponding mechanisms of plants for salt stress.