ABSTRACT
In this study, the fatty acid desaturase gene FAD2 was cloned from Coix lacryma-jobi L. and its molecular structure and function were studied. The results showed that the full-length cDNA sequence of FAD2 gene was 936 bp encoding 311 amino acid residues. Bioinformatics prediction results showed that the protein encoded by the FAD2 gene was an alkaline hydrophilic unstable protein with a molecular weight of 34.87 kDa. It contained three transmembrane helix domain, and did not contain the signal peptide splicing site, and was most likely to be located in plasmid membrane. Compared with other similar genes in plants, it has only a histidine conserved site, His Box Ⅲ histidine site (HXXHH), suggesting its activity may be reduced. Phylogenetic tree analysis showed that FAD2 was closely related to monocotyledonous plants, especially Maize and Oryza sativa japonica Group, but farther from dicotyledonous plants. Therefore, it was inferred that FAD2 might have similar functions with similar genes in Maize and Oryza sativa japonica Group. In addition, the expression of FAD2 gene could be detected in Coix lacryma-jobi L. with high oil content, but not in low oil content of Coix lacryma-jobi L. In order to clarify the function of FAD2, the gene was heterologously expressed in sporomyces cerevisiae. The results showed that the protein encoded by FAD2 gene did not catalyze the formation of C18∶1 unsaturated fatty acid into C18∶2 unsaturated fatty acid. Therefore, it was speculated that the deletion of histidinine conserved site of FAD2 gene might lead to the decrease of protein activity or even inactivation. This study provides reference value for further understanding the molecular structure characteristics of fatty acid desaturase. At the same time, it laid a foundation for elucidating the biosynthetic pathway of Coix lacryma-jobi L.
ABSTRACT
Iridoid synthase( IS),the key enzyme in the natural biosynthesis of vegetal iridoids,catalyzes the irreversible cyclization of 10-oxogeranial to epi-iridodial. In this study,we screened the Rehmannia glutinosa transcriptome data by BLASTn with Catharanthus roseus CrIS cDNA,and found four c DNA fragments with length of 1 527,1 743,1 425,1 718 bp,named RgIS1,RgIS2,RgIS3 and RgIS4,respectively. Bioinformatics analysis revealed that the four iridoid synthase genes encoding proteins with 389-392 amino acid residues,protein molecular weights were between 44. 30-44. 74 k Da,and theoretical isoelectric points were between 5. 30 and 5. 87. Subcellular localization predictions showed that the four iridoid synthase were distributed in the cytoplasm. Structure analysis revealed that R. glutinosa iridoid synthases contain six conserved short-chain dehydrogenase/reductase( SDR) motifs,and their 3 D models were composed typical dinucleotide-binding " Rossmann" folds covered by helical C-terminal extensions. Using the amino acid sequences of four R. glutinosa iridoid synthases,phylogenetic analysis was performed,the result indicated that RgIS3,CrIS and Olea europaea OeIS were grouped together,the other R. glutinosa iridoid synthases and fifteen proteins in other plants had close relationship. Real-time fluorescent quantitative PCR revealed that RgIS1 and RgIS3 highly expressed in unfold leaves,however,RgIS2 and RgIS4 highly expressed in stems and tuberous roots,respectively. RgIS3 showed higher expression levels in non-radial striations( nRS) of the two cultivars,and RgIS1 and RgIS2 had higher expression levels in nRS of QH,while RgIS4 had less expression levels in nRS of QH1. RgIS1,RgIS2 and RgIS3 were up-regulated by Me JA treatment,although the time and degree of response differed. Our findings are helpful to reveal molecular function of R. glutinosa iridoid synthases and provide a clue for studing the molecular mechanism of iridoid biosynthesis.
Subject(s)
Cloning, Molecular , Genes, Plant , Iridoids , Metabolism , Ligases , Genetics , Phylogeny , Rehmannia , GeneticsABSTRACT
A Staphylococcus aureus JH strain which can produce lipase was obtained from environment.According to polysequence comparision of prokaryote’s lipase gene published on NCBI,its sequence is very conservative. Lipase gene was obtained by PCR from genome DNA of Staphylococcus aureus JH,and then it was incorporated into plasmid pC194 and transformed into B.subtilisH11 .The recombinant lipase precipitated by(NH4)2SO4, purified by ion exchange chromatography and was identified by SDS-PAGE.It was revealed that the molecular mass of the recombinant lipase is 32kDa;the recombinant lipase show maximum activity at 41℃,pH8.0;the values of Km and Vm were found to be 0.34mmol/L and 308?mol/mg.min;The lipase can be activated by the metal ions Ca2+,K+ and Mg2+ and be inhibited by Fe2+,Cu2+,and Co2+.