title: Overexpression of GmAKT2 potassium channel enhances resistance to soybean mosaic virus.
abstract: BACKGROUND
  Soybean mosaic virus (SMV) is the most prevalent viral disease in many soybean production areas. Due to a large number of SMV resistant loci and alleles, SMV strains and the rapid evolution in avirulence/effector genes, traditional breeding for SMV resistance is complex. Genetic engineering is an effective alternative method for improving SMV resistance in soybean. Potassium (K+) is the most abundant inorganic solute in plant cells, and is involved in plant responses to abiotic and biotic stresses. Studies have shown that altering the level of K+ status can reduce the spread of the viral diseases. Thus K+ transporters are putative candidates to target for soybean virus resistance.
  
  
  RESULTS
  The addition of K+ fertilizer significantly reduced SMV incidence. Analysis of K+ channel gene expression indicated that GmAKT2, the ortholog of Arabidopsis K+ weak channel encoding gene AKT2, was significantly induced by SMV inoculation in the SMV highly-resistant genotype Rsmv1, but not in the susceptible genotype Ssmv1. Transgenic soybean plants overexpressing GmAKT2 were produced and verified by Southern blot and RT-PCR analysis. Analysis of K+ concentrations on different leaves of both the transgenic and the wildtype (Williams 82) plants revealed that overexpression of GmAKT2 significantly increased K+ concentrations in young leaves of plants. In contrast, K+ concentrations in the old leaves of the GmAKT2-Oe plants were significantly lower than those in WT plants. These results indicated that GmAKT2 acted as a K+ transporter and affected the distribution of K+ in soybean plants. Starting from 14 days after inoculation (DAI) of SMV G7, severe mosaic symptoms were observed on the WT leaves. In contrast, the GmAKT2-Oe plants showed no symptom of SMV infection. At 14 and 28 DAI, the amount of SMV RNA in WT plants increased 200- and 260- fold relative to GmAKT2-Oe plants at each time point. Thus, SMV development was significantly retarded in GmAKT2-overexpressing transgenic soybean plants.
  
  
  CONCLUSIONS
  Overexpression of GmAKT2 significantly enhanced SMV resistance in transgenic soybean. Thus, alteration of K+ transporter expression is a novel molecular approach for enhancing SMV resistance in soybean.
authors.forename: Lian
authors.initials: L
authors.lastname: Zhou
authors.forename: Hongli
authors.initials: H
authors.lastname: He
authors.forename: Ruifang
authors.initials: R
authors.lastname: Liu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Han
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, P, R, China. huixia@zju.edu.cn.
authors.forename: Huixia
authors.initials: H
authors.lastname: Shou
authors.forename: Bao
authors.initials: B
authors.lastname: Liu
mesh_terms: D060467:Disease Resistance / Q000187:drug effects / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005838:Genotype; D009029:Mosaic Viruses / Q000187:drug effects / Q000502:physiology*; D010935:Plant Diseases / Q000235:genetics / Q000821:virology*; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D015203:Reproducibility of Results; D013025:Glycine max / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000821:virology*
chemical_list: D010940:Plant Proteins; D015221:Potassium Channels; D011188:Potassium