First genetic insight into sexual dimorphism and sex determination in Eucommia ulmoides(Eucommiaceae)

【摘要】：Eucommia ulmoides is a model representative of the dioecious plants with sex differentiation at initiation.Nevertheless,the genetic mechanisms of sexual dimorphism and sex determination in E.ulmoides remain poorly understood.In this study de novo transcriptome sequencing on Illumina platform generated 45 billion high-quality bases from three males and three females of E.ulmoides.A total of 148,595 unigenes with an average length of 801 bp were assembled.Through comparative transcriptome analyses,116 differentially expressed genes(DEGs) between the males and the females were detected,including 73 male-biased genes and 43 female-biased genes.Of these DEGs,three female-biased genes were likely related to the sexually dimorphic gutta(Eu-rubber) content in E.ulmoides.Particularly,we found one female-biased gene shares high homology with RDM1 gene,which is an indispensable factor for the canonical RdDM pathway,suggesting the epigenetic regulation may play a key role in shaping the sexual dimorphism of E.ulmoides.Moreover,one male-biased DEG was identified as putative MADS box gene APETALA3,a B class floral organ identity gene in the flowering plants.SNPs calling analyses further confirmed that the APETALA3-like gene was probably involved in the sex determination in E.ulmoides.In addition,four other male-biased DEGs were potential sex-linked genes as well with segregated SNPs in accord with sex type.The estimated SNPs density in the expressed genes of E.ulmoides was 1.02/kb,implying a relatively high genetic diversity.