Submitted to: Biomed Central (BMC) Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 15, 2012
Publication Date: February 29, 2012
Citation: Zhou, X., Fei, Z., Thannhauser, T.W., Li, L. 2012. Transcriptome analysis of ectopic chloroplast development in green curd cauliflower (Brassica oleracea L. var. botrytis). Biomed Central (BMC) Plant Biology. 11:169. Interpretive Summary: Chloroplasts are green plastids found in plants, where photosynthesis and some other important metabolisms take place. Chloroplast biogenesis is a complex process that requires coordination of expression of many genes and is highly regulated by the developmental and environmental cues. This study was carried out to investigate the control of chloroplast development using a novel green curd cauliflower mutant. The genome-wide profiling of gene expression in the curd tissues led to the identification of a large number of genes associated for chloroplast development and suggests the critical role of certain regulatory genes in mediating the chloroplast development in the green curd cauliflower mutant. Our results also indicate that RNA-seq as a powerful tool could speed up functional identification of genes for the dissecting of genetic basis of naturally-occurring variations in crops.
Technical Abstract: Chloroplasts are the green plastids where photosynthesis takes place. The biogenesis of chloroplasts requires the coordinate expression of both nuclear and chloroplast genes and is regulated by developmental and environmental signals. Despite extensive studies of this process, the genetic basis and the regulatory control of chloroplast biogenesis and development remain to be elucidated. Green cauliflower mutant causes ectopic development of chloroplasts in the curd tissue of the plant, turning the otherwise white curd green. To investigate the transcriptional control of chloroplast development, we compared gene expression between green and white curds using the RNA-seq approach. Deep sequencing produced over 15 million reads with lengths of 86 base pairs from each cDNA library. A total of 7,155 genes were found to exhibit at least 3-fold changes in expression between green and white curds. These included light-regulated genes, genes encoding chloroplast constituents, and genes involved in chlorophyll biosynthesis. Moreover, we discovered that the cauliflower ELONGATED HYPOCOTYL5 (BoHY5) was expressed higher in green curds than white curds and that 2616 HY5-targeted genes, including 1600 up-regulated genes and 1016 down-regulated genes, were differently expressed in green in comparison to white curd tissue. All these 1600 up-regulated genes were HY5-targeted genes in the light. The genome-wide profiling of gene expression by RNA-seq in green curds led to the identification of large numbers of genes associated with chloroplast development, and suggested the role of regulatory genes in the high hierarchy of light signaling pathways in mediating the ectopic chloroplast development in the green curd cauliflower mutant.