Transcriptome And MiRNA Analyses Of Papaya Sex Differentiation

Papaya(Carica papaya L.)is a trioecious plant with three sex types:male,female and hermaphrodite.The cultivars of papaya are mainly gynodioecious plants with female and hermaphrodite,and the wild type papaya is dioecism.Gender evolution is one of the important processes of plant growth and development,and miRNA(mircoRNA)can also regulate the expression of sex by controlling a series of physiological and biochemical processes such as endogenous hormone synthesis and signal transduction.The nascent sex chromosomes of papaya provides an opportunity for studying sex chromosome evolution in plants.Genomic researches have confirmed that cultivars are evolved from wild MSY3 populationsIn order to reveal the dynamic expression of genes and functional differences on mRNA and miRNA level between hermaphrodite of SunUp and the female and male of wild type MSY3 for exploring genes related to sex differentiation by high-throughput sequencing.It has important practical applications to breeding and reducing cultivation costs.The main results and conclusions are as follows.1.At the level of mRNA,the RNA-seq analysis for the expression of transcriptome between cultivated species SunUp hermaphrodite(SU_H),wild type MSY3 female(MSY3_F)and male(MSY3_M).The whole genome of the SU_H and MSY3_F plants were the most differentially expressed(1734);it was revealed that most of the DEGs(differentially expressed genes)involved in gibberellin,abscisic acid,jasmonic acid hormones related genes,and mainly in SU_H plants with the up-regulated expression by the functional analysis of DEGs.At the same time,DEGs involved in fatty acid elongation,plant hormone signal transduction and photosynthesis biological processes had very significant transcriptional abundances in three sex plants,especially DEGs that were involved in lipid metabolism,maybe associated with papaya stamens abortion.These results indicated that the sex differentiation of papaya is regulated by lipids,hormones(abscisic acid,jasmonic acid,gibberellin)and photosynthetic biological processes.2.At the level of microRNA,the miRNA identification and target gene prediction were by differentially analysis of the miRNA of Sun Up_H,MSY3_F and MSY3_M.In total,there are 68 homologous conserved miRNAs and 33 new predicted miRNAs,including the most miR396 families.The results showed that miRNAs were involved in the growth and sex differentiation of papaya by a complex regulatory network,in which miR156,miR160d,miR396 and miR319 were associated with pollen development and showed specific expression in MSY3_M,and miR167 in SU_H plants with high expression,indicating that miR396 can promote male development.In addition,the transcription factor GRF was negatively regulated by miR396,resulting in papaya pistil development abnormalities.Through the functional analysis of the target gene,miR395 can regulate the activity of active oxygen in plants and involvement of lipid metabolism pathway.The miR396 regulates the glutathione transferase(GST)to repair papaya plants leading to changes in endogenous hormones that cause papaya sex differentiation.The results of the above gene expression analyses showed that plant hormones,lipid metabolic pathways interected with photosynthetic biological processes to form a complex regulatory network to regulate papaya sex differentiation at the mRNA and microRNA levels.