SRA

Purpose: The goals of this study are to analyze the transcriptome of five time point in broccoli seed germination and sprout development and to find the putative glucosinolate metabolism genes in the stage. Methods: Total mRNA of germinated seeds, 3 day cotyledons, 7 day botyledons, 11 day cotyledons and 11 day euphyllas of wild-type broccoli were harvested. Each sample was harvested in three independent biological replicates with equal weight and subsequently pooled together for sequencing. The sequence reads that passed quality filters were de novo assembled using VELVET followed by OASES. Then the assembled unigenes were used for the abundance and functional analysis. Results: A total of ~85million 251bp reads were obtained. After de novo assembly and searching the assembled transcripts against the Arabidopsis thaliana and Nr databases, 19,441 top-hit transcripts were clustered as unigenes with an average length of 2,133bp. These unigenes were classified according to their putative functional categories. Cluster analysis of total unigenes with similar expression patterns and differentially expressed unigenes among different tissues,as well as transcription factor analysis were performed. We identified 25 putative glucosinolate metabolismgenes sharing 62.04-89.72% nucleotide sequence identity with the Arabidopsis orthologs. This established a broccoli glucosinolate metabolic pathway with high colinearity to Arabidopsis. Many of the biosynthetic and degradation genes showed higher expression after germination than in seeds; especially the expression of the myrosinaseTGG2 was 20-130 times higher.These results along with the previous reports that glucosinolate concentration decreased exponentially once after germination indicate the breakdown products of glucosinolates may play important roles in broccoli seed germination and sprout development. Conclusion: Our study provides the largest genetic resource of broccoli to date. These data will pave the way for further studies and genetic engineering of broccoli sprouts to develop functional vegetables containing high levels of the anticarcinogenic glucosinolates. They will also provide new insight into the genomic research of this species and its relatives. Overall design: Wild-type broccoli mRNA profiles of seeds, 3 day cotyledons, 7 day botyledons, 11 day cotyledons and 11 day euphyllas were generated by deep sequencing, three biological replicates pooling together for each tissue, using Illumina Myseq platform.