Functional Analysis Of AtKEA4,AtKEA5 And AtKEA6 In Arabidopsis Thaliana

The AtKEA gene family contains six members.Sequence analysis shows that AtKEAs are homolog of the bacterial K~+/H~+antiporter Ec Kef B and Ec Kef C,indicating that AtKEAs may encode K~+/H~+antiporters in Arabidopsis.Recent studies indicate that AtKEA1,AtKEA2 and AtKEA3 are localized in the chloroplasts;these antiporters regulate p H homeostasis and ion transport in chloroplasts and improve photosynthetic efficiency.However,the function of AtKEA4,AtKEA5 and AtKEA6 remains largely unknown.In order to understand the role of AtKEA4,AtKEA5 and AtKEA6 in growth and development,we identified the single mutants kea4-1,kea5-1and kea6-1,and prepared double mutants and a triple mutant by genetic crossing.We then analyzed the phenotype of these mutants.The major results are listed below:1.Using the“Tri-Primer-PCR”method,we identified the single mutants kea4-1,kea5-1,kea6-1.We prepared the double mutants kea4-1 kea5-1,kea4-1 kea6-1 and kea5-1 kea6-1 by genetic crossing.We then obtained the triple mutant kea4-1 kea5-1 kea6-1 by crossing kea4-1 kea6-1 with kea5-1.2.Growth analysis showed that the kea4 kea5 kea6 triple mutant was short relative to the wild type plants.In addition,it had short rosette leaves and short siliques.It had less leaves compared to the wild type.These results indicate that AtKEA4,AtKEA5 and AtKEA6 regulate growth and development.3.We observed the effect of Na Cl stress on the growth of the kea 4 kea 5 kea 6 triple mutants grown on the 1/2 MS medium.We found that root growth of kea 4 kea 5 kea 6 was inhibited under the treatment of 100 m M and 150 m M Na Cl.Consistently,kea 4 kea 5 kea 6 showed growth retardation when grown in soil under Na Cl stress.The seedlings were short and bolting late,and had smaller rosette leaves.Some leaves became yellow,white,and even desiccated.These results indicate that AtKEA4,AtKEA5 and AtKEA6 play an important role in salt tolerance in plants.4.Growth analysis showed that the root growth of the triple mutant kea 4 kea 5 kea 6 was inhibited under acidic conditions(pH 4.0);under alkaline conditions(p H 8.0),however,root growth in kea 4 kea 5 kea 6 restored to the wild type level.These results indicate that AtKEA4,AtKEA5 and AtKEA6 may regulate p H homeostasis.In conclusion,our study indicates that AtKEA4,AtKEA5 and AtKEA6 play an important role in p H homeostasis and salt tolerance in Arabidopsis.