Comparative Transcriptome Analysis Between ISF Line And Pistillate Line In Ricinus Communis L.

The pistillate line is the main approach for utilizing heterosis and the ISF(interspersed staminate flower)line is the most important and effective means for reproducing pistillate line in castor.Because of the instability of ISF on expression and the limited knowledge to its genetic and physiological mechanism,its application in breeding and production is restricted.Studying the physiological differences between the ISF line and the pistillate line will contribute to the sex expression regulation and its breeding application.In this study,firstly,the relative content of chlorophyll,net photosynthetic rate,soluble nutrients and endogenous hormones in leaves were analyzed in the bud stage and full-bloom stage using the highly homozygous ISF line and pistillate line with the same genetic background.Secondly,the comparative transcriptome analysis was performed betwen ISF line and pistillate line at the bud stage,flowering stage and full-bloom stage.The results were as follows.1.In bud stage,the significantly higher soluble sugar and cytokinin content,increased by 36.9%?61.5%,and the significantly lowered gibberellin content in ISF line,decreased by 25.6%.In full-bloom stage,the relative chlorophyll content,net photosynthetic rate,gibberellin,auxin and ethylene content were significantly increased in ISF line than those in pistillate line,increased by 15.2%,23.3%,13.8%,33.5% and 73.8%,while the contents of soluble sugar,soluble starch and abscisic acid were significantly decreased,declined by 38.0%?54.9%?14.8%.It could be concluded that the formation of ISF was characterized by the increase of soluble sugar and cytokinin firstly,followed by the obvious increase of nutrient consumption,chlorophyll content,net photosynthetic rate,the concentration of gibberellin,auxin and ethylene,and the decrease of abscisic acid concentration.2.The comparative analysis of gene expression showed that there were 45 differentially expressed genes in bud stage,including 22 up-regulated genes and 23down-regulated genes.In the flowering stage,there were 45 differentially expressed genes,including 351 up-regulated genes and 34 down-regulated genes were found.In the full-bloom stage,there were 45 differentially expressed genes,including 88 genes were up-regulated and 416 genes were down-regulated.3.The GO analysis of the differentially expressed genes between ISF line and pistillate line showed that the sex differentiation of castor bean was related to amino acidmetabolism,DNA binding,ethylene activity signaling pathway,hormone response,transcriptional regulation activity,organic catabolism and other genes.4.KEGG enrichment revealed that two pathways(amino sugar and nucleotide sugar metabolic pathways)in bud stage,14 pathways(biosynthesis of secondary metabolites,tyrosine metabolism,phenylalanine metabolism,tryptophan metabolism,etc.)in flowering stage and five pathways(plant pathogen interaction,fatty acid elongation,plant MAPK signal transduction pathway,plant hormone signal transduction,and biosynthesis of secondary metabolites)in full-bloom stage were involved in sex differentiation between ISF line and pistillate line.5.The annotated classification by KOG between ISF line and pistillate line mainly focused on carbohydrate transport and metabolism,signal transduction mechanism,general function prediction,synthesis,transportation and metabolic decomposition of secondary metabolites.Carbohydrate and its signal transduction mechanisms showed significant differences at different stages of inflorescence differentiation.