Analysis of the transcriptome of normal and mutant willow-shaped leaves of Ricinus communis using high-throughput RNA sequencing

Ricinus communis is the source of castor oil and widely used. Lm type female strains of castor were mutants of castor which showed some phenotypes including typical willow-shaped leaves morphological characteristics, while leaves on the normal bisexual strain in Ricinus communis are palmar. To date, the molecular mechanisms responsible for the growth of the typical willow-shaped leaves have not yet been clarified. In this study, we performed transcriptome analysis to explore differentially expressed genes (DEGs) between normal palm-shaped leaves and mutant willow-shaped ones. Through high-throughput RNA sequencing, a total of 155,862 unigenes were finally annotated after assembly, and 1,530 DEGs in the mutants were identified, in which 1,205 DEGs were up-regulated and 325 DEGs were down-regulated. Gene Ontology (GO) Classification divided the unigenes and DEGs into 3 main categories, i.e. molecular function, biological process and cell component. According to the COG analysis, most of the unigenes were classified into the 'general function prediction only'. Some interesting candidate genes that may contribute to the formation of willow-shaped leaves such as C179712, C271005, C99773 and C241332 were verified using quantitative real-time PCR (qRT-PCR) analysis, and the results were in agreement with that in the RNA-Seq which confirmed the reliability of the RNA-seq data. These results laid the foundation for studying the mechanism responsible for the formation of the willow-shaped leaves.