The nucleotide sequence and derived amino acid sequence of two different beta-glucosidase cDNA clones were determined. One clone (TRE104) was identified as the cyanogenic beta-glucosidase by homology with the N-terminal and internal peptide amino acid sequence of the purified enzyme. The biological function of the other beta-glycosidase (TRE361) is not known. Co-segregation of genomic restriction fragments uniquely identified by each cDNA clone shows that these two genes are linked in the white clover genome. Both TRE104 and TRE361 fragments co-segregate with cyanogenic beta-glucosidase activity. Extensive homology was found between the white clover beta-glucosidase sequences and a group of prokaryote and mammalian beta-glycosidases. This group of sequences has no homology with a separate set of beta-glucosidase genes isolated from fungi and the thermophilic bacterium Clostridium thermocellum.
Molecular Phylogenetic Studies in Providing BasicKnowledge to Improve Quality of Genetic Resources of Orchid. Topik Hidayat and Adi Pancoro. Early information resulted from molecular phylogenetic studies of many important ornamental crops is often less attention to many growers and farmers. Phylogenetics is one of the most preferable method in systematics to reconstruct evolutionary relationships of groups of biological organisms in order to understand their biodiversities. This has been revolutionized by DNA sequences data. In this method, a group of organisms that shares many identical characteristics are considered to be closely related; deriving from a common ancestor and is assumed to have similar genetic patterns and biochemical properties. By these basic principles, molecular phylogenetics plays important roles in revealing a basic knowledge on pattern of relationships to which genetic resources can be improved. Over the past decade, botanists have done several thousand phylogenetic analyses based on molecular data of economically and horticulturally important crops. Orchids are the best example for this. There is no doubt that most orchid plants had played roles in horticulture and hybridization. At present, many infrageneric and intergeneric hybrids are available commercially. Successful hybridization can be achieved if two or more individual plants understudy are closely related in respect to their genetics and evolution.
The Li locus in white clover controls the presence of cyanogenic beta-glucosidase (linamarase) activity in leaf tissue, such that plants homozygous for the 'null' allele (li) have no linamarase activity in this tissue. The isolation of a cDNA clone from linamarase mRNA is described. The cDNA clone is used to further characterise alleles of the Li locus. Northern blot analysis shows that plants homozygous for the 'null' allele (li li) produce very reduced levels of mRNA which hybridises to the cDNA. Heterozygous plants (Li li), which have intermediate levels of enzyme activity, produce intermediate levels of mRNA. Southern blot analysis of Hind III digested genomic DNA shows that the white clover genome contains three genes with homology to the linamarase cDNA and that at least two of these genes segregate independently. Analysis of the cosegregation of linamarase activity and the presence of genomic restriction fragments identifies the genomic sequence specifying linamarase structure and indicates either a structural or cis acting control function of the Li locus.
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