Cloning And Expression Analysis Of Silicon Transporter Genes In Roots Of Rootstocks For Cucumber Grafting

Cucumber(Cucumis sativus L.)is one of the main facility cultivation vegetables. Bloom on fruit is an important commodity character of cucumber. The content of the bloom on the surface of the cucumber and grafted cucumber with different rootstocks were different, in which the silicon metabolism in roots plays a major role. To study the relationship between silicon absorption transfer mechanism and bloom formation on fruit surface of cucumber. This study cloned silicon transporter genes CmLsi1, CmLsi2 and CmLsi3 from the weak de-blooming ability rootstock cultivar ‘Yunnan figleaf gourd’ and the strong de-blooming ability rootstock cultivar ‘HuangchenggenNo.2’ roots, respectively. In addition, this research studied the silicon transporter genes expression pattern. The results are as follows:(1) The full-length cDNA sequences of CmLsi1 and CmLsi2, which were cloned from the weak de-blooming ability rootstock cultivar ‘Yunnan figleaf gourd’ and the strong de-blooming ability rootstock cultivar ‘HuangchenggenNo.2’ roots, were no difference with those in the NCBI. The full-length cDNA sequences of CmLsi3 was also cloned from this two pumpkin cultivars and the Gen Bank accession number were KM203110 and KM359142, respectively.(2) The full-length cDNA of Cmlsi3 from ‘Yunnan figleaf gourd’ and ‘Huang chenggen No.2’ were 795 bp and encoded 264 amino acids. Comparison of the two sequences revealed that differed in four amino acids. The predicted Cmlsi3 amino acid sequences shared at least 50% identity with those of cucumber, maize, barley. Analysis the CmLsi3 protein structure showed that contained typical two asparagine-proline-alanine(NPA) motifs, six transmembrane domains and a distinct ar/R(aromatic/arginine) selectivity filter composed from Gly(G), Ser(S), Gly(G) and Arg(R).Therefore,CmLsi3 protein belonged to nodulin 26-like intrinsic membrane proteinⅢ(NIPⅢ) subgroup of plant aquaporin.(3) CmLsi3 gene was expressed in the roots, stems and leaves, but the expression was hightest in leaves and lowest in roots,the stems in the middle. The expression level of CmLsi3 in different organs were higher in ‘Yunnan figleaf gourd’ than in ‘HuangchenggenNo.2’.(4) The expression level of CmLsi1(B+),CmLsi2-1,CmLsi2-2 and CmLsi3 in ‘Yunnan figleaf gourd’ own-root and its grafted cucumber were declined by 1.7mM silicon supply. But the expression level of CmLsi1(B-),CmLsi2-1,CmLsi2-2 and CmLsi3 in ‘Huangchenggen No.2’ owned-root and its grafted cucumber were unaffected by silicon supply.