Silkworm Unfertilized Oocytes Expressed Sequence Tag (est) Analysis

Silkworm (Bombyx mori) is a basic biologic unit of the sericulture, EST(expressed sequence tag) sequencing can obtain detailed information concerned on molecular level and supply the silkworm's genomic structure and the information of most genes. It is a significant case study valuable for the further achievement.The collections of silkworm's EST database have great contribution in discovery of new genes and study of genes kick off and preparation of gene chip. This study constructed cDNA libraries from the silkworm's kidney and normal unfertilized eggs ,these cells of unfertilized eggs express plenty of information regarding with early embryo development.Maternal genes are the decisive genes which are stored in unfertilized eggs and affect offspring's development. They transcript during oogenesis and translate during oogenesis or embryogenesis. Maternal genes are responsible for controlling the axis specification, cleavage pattern, morphogenetic movements in the early embryo development. In the development of insects, the anterior-posterior and dorsal-ventral of embryo are determined by maternal genes' products independently. These maternal genes mainly encode transcript fators or regulative proteins, their products usually form specific concentrative gradient and produce locational information. The information activates the expression of a series of zygotic genes, then the embryo is devided to different regions. The combination of specific genes expressed at different parts form definite segment polarity through anterior-posterior or dorsal-ventral. The mRNAs and proteins in the unfertilized eggs are maternal genes' products.The primary data were masked out the vector sequence, then wiped off low quality and smaller than 1OObp sequences. These EST sequences were assembled by clusterW. The six frame translations of the EST sequences were compared to the GenBank non-redundant collection of 1,230,998 protein sequences using the function blastx. In addition, the EST sequenceswere compared to the 1,453,916 non-redundant nucleotide sequences in GeneBank using the function blastn. Through blastx and blastn to find similarity between ESTs with protein or nucleotide sequences, We also used SMART to analyse the domains of some genes, in which amino acid sequence have known, with unknown functions, then deduced their characters and functions. In addition, the EST sequences were compared with the 28 cDNA databases's EST sequences in silkbase. Functional catalogue of known genes were classified by Gene Ontology.At last, we have successfully sequeced 391 ESTs , with an average length of 659bp . After assembling by clusterW , we obtained 374 unigenes, the largest unigene was composed of four ESTs, the longest unigene was 1958bp. There are 15 contigs in the unigenes, 118 singlets are ESTs from normal unfertilized eggs, the other 241 are ESTs from kidney unfertilized eggs.Through large scale sequencing and analysing, we obtained lots of information about functional genes. The bioinformatic analyse found that 171 unigenes have significant similarities with known genes, 25 have significant similarities with known EST sequences, the other 178 have low or no similarities with known genes or EST sequences.The unfertilized eggs cDNA libraries provide a lot of maternal information, most of them except three known maternal genes are relate to replication, metabolism, conduction and embryo development, the three maternal genes are BmVLG,capu and annexin bl3. These useful information provide sequence information for the study of functional genes and maternal genes' function and is helpful for basic data of regulation during the early embryo development of silkworm and accelerate the study of silkworm's functional genome.