Potassium Channel Protein Gene SeAKT1 Improves Potassium Nutrition Of Transgenic Maize

Potassium(K~+)is a monovalent cation abundant in plant cells,which is of great significance in plant growth.At present,potassium deficiency in cultivated soil is very serious in our country and a large amount of potassium fertilizer is imported.Maize plays an important role in food,feed and industry.However,insufficient supply of potassium leads to weak seeding and shrivelled seeds,thus seriously affects yield and quality of maize.Therefore,how to improve the absorption capacity of potassium in maize under low potassium condition becomes a problem that needs to be solved urgently.Potassium ion channel is the main way for plants to absorb potassium.Overexpression of potassium channel protein gene AKT1 enhances the uptake capacity of potassium in plants.SeAKT1,a potassium channel protein gene,was cloned from Salicornia europaea and transformed into Arabidopsis thaliana to confirm its function in our laboratory.The recombinant plasmid ubi:SeAKT1 was transferred into maize by Agrobacterium-mediated immature embryo infection,and five positive transformation events were obtained.The results of PCR and bar strip detection showed that the target gene SeAKT1 and screening marker gene bar had been transferred into maize,and the bar gene was expressed at the protein level.Semi-quantitative RT-PCR analysis was carried out and the results showed that SeAKT1gene was expressed in all three lines,which were obtained by hybridized with maize backbone inbred line PH6WC.PCR screening and Chi-square test were performed and the results showed that the gene segregation ratio was in accordance with Mendelian segregation law in these three lines.Depletion experiment of L1 and L3 lines were carried out,in which the samples were taken every 4 h during a 28 h period.The results showed that transgenic maize plants had higher potassium uptake capacity than the wild type at 0.1 mM potassium concentration.Liquid culture experiment was carried out on L3 line for 4 weeks,plant height,root length,fresh weight and dry weight of shoots and roots,and potassium content were measured.The results showed that at 3 mM potassium concentration,except root length and dry weight of shoots,the indexes of transgenic maize plant were significantly higher than those of the wild type.At 0.1 mM low potassium stress,except plant height and potassium concentration in roots,the indexes of transgenic maize plant were significantly higher than those of the wild type.These results suggest that SeAKT1 is a potassium channel protein with dual-affinity and the SeAKT1transgenic maize plants have higher potassium uptake capacity,which lead to the increase of their biomass.Field trial was carried out on L1 line.At the silking stage,plant height,spike position and leaf area were measured.At the mature stage,spike length,spike diameter,row number,row grain number,hundred-grain weight and spike weight were counted.The results showed that when available potassium in soil was 100 mg/kg,the spike position of transgenic maize plant was significantly lower than that of the wild type,while the row grain number was significantly higher than that of the wild type.When available potassium in soil was 80 mg/kg,the spike length and hundred-grain weight of transgenic maize plant were significantly higher than those of the wild type.When available potassium in soil was 30 mg/kg,the spike length and spike weight of the transgenic maize plant were significantly higher than those of the wild type,so it is speculated that the spike weight might be increased by increasing spike length.The above results indicate that the overexpression of SeAKT1 gene enhances the potassium absorption capacity of transgenic maize plants which improves their biomass and yield related characters.