I have some data on ncbi Sequence Read Archive ( SRX160526 ): Sequenced the transcriptomes of susceptible, resistant, herbicide-treated susceptible and herbicide-treated resistant barnyardgrass biotypes using the 454 GS-FLX platform. Although there are FOUR plant biotypes, there is only one *.sra file. How can I assembly this transcriptome without the reference genome using the de novo assembly method?