The Interactive Effects Of Arbuscular Mycorrhizal Fungus And Potassium Application On Lycium Barbarum L.responding To Drought Stress

A pot experiment was conducted to study the interactive effects of arbuscular mycorrhizal fungus and potassium application on the physiological characteristics of Lycium barbarum L. responding to drought stress. Using RT-PCR method, we cloned four potassium channel genes of L. barbarum and explored the effects of AMF and potassium application on the expression patterns of these genes responding to drought stress by q RT-PCR. The main results as follows:1. The effects of AMF and potassium application on the physiological characteristics of L.barbarum responding to drought stressMycorrhizal colonization rates gradually increased with the increasing of potassium application under drought stress, reaching the significant level at K2, improved up 11.5% and9.9% by comparing to the K0 and K1 respectively. The growth and potassium content in root and leaf of L. barbarum were increased by AMF and potassium application.Potassium application dramatically increased the Fv/Fm, ФPSII, ETR and decreased the q N of leaf respectively under drought stress. AMF notably enhanced the Fv/Fm, ФPSII, ETR,q P at different exogenous potassium levels, and dramatically reduced the q N.The SOD, POD activities were dramatically enhanced along the rising of potassium application under drought stress, apart from the CAT activity. The SOD, POD activities in leaf were only significantly improved by AMF at K1 level. The CAT activity was increased with AMF colonization by 51.2% and 11.9% at K0 and K1, respectively.2. Cloning and expression analysis of L. barbarum Lb KT1 and Lb SKOR potassium channel genesThe results of LbKT1 and LbSKOR indicated that: The ORF length of LbKT1 and Lb SKOR were 2661 bp and 2448 bp, which encode proteins with 886 and 815 amino acid residues, the theoretical p I were 6.78 and 6.34 respectively. Sequence prediction indicated that Lb KT1 and Lb SKOR located in plasma membrane with transmembrane domain, c NMP binding domain and ion-trans domain, the potassium channel protein signature segunce Txx Tx GYGD was located in P ring. Polygenetic tree analysis of amino acid sequences showed that Lb KT1 belongs to the AKT1 subfamily of Shaker family with a high homology to the amino acid sequence of tomato and potato KT1, the Lb SKOR belongs SKOR subfamily of Shaker family.Organ-specific analysis suggested that Lb KT1 and Lb SKOR expressed in L. barbarum roots, stems and leaves, but with highest level in roots. q RT-PCR analysis clarified inoculation of AMF significantly increased the relative expression level of Lb KT1 and Lb SKOR in roots under drought stress, the Lb KT1 was increased by 50.8% and 80.6%, the Lb SKOR expression level was improved by 67.5% and 121.8% at K1 and K2 compared to K0.3. Cloning and expression analysis of L. barbarum Lb TPK1 and Lb TPK3 potassium channel genesThe results of Lb TPK1 and Lb TPK3 indicated that: The ORF length of Lb TPK1 and Lb TPK3 were 1050 bp and 1233 bp, which encode proteins with 349 and 410 amino acid residues, the theoretical p I were 5.84 and 7.61 respectively. Subcelluar location prediction indicated that Lb TPK1 and Lb TPK3 located in tonoplast membrane; the instability index prediction showed that two potassium channel proteins were stable proteins. Structural domains prediction indicated that Lb TPK1 and Lb TPK3 contained the ion-trans domains and potassium channel protein signature segunce Txx Tx GYGD, which was located in P ring.Polygenetic tree analysis of amino acid sequences showed that Lb TPK1 and Lb TPK3 belong to the TPK family with a high homology to the TPK amino acid sequence of tomato and potato.Organ-specific analysis suggested that Lb TPK1 and Lb TPK3 all expressed in L.barbarum roots, stems and leaves, but with highest level in leaves. q RT-PCR analysis clarified inoculation of AMF significantly increased the relative expression level of Lb TPK1 in leaves under drought stress at K2 by 39.3%, but haved no significant influence to Lb TPK3.