Transcriptome analysis of the male-to-hermaphrodite sex reversal induced by low temperature in papaya
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Papaya (Carica papaya L.) is a trioecious plant species, producing three sex forms, male, female, and hermaphrodite. Although the major sex types are genetically determined, the phenotypic sex expression of papaya is influenced by environmental factors. We investigated differential gene expression analysis between the non-functional rudimentary pistils from normal male flowers and developed and functional pistils from the male-to-hermaphrodite sex reversal flowers induced by low temperature aiming to understanding the gene regulatory network that determinates the phenotypic sex expression in papaya. Our differential gene expression analysis revealed 1756 differentially expressed genes between normal male and male-to-hermaphrodite sex reversal flowers. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genome (KEGG) pathway enrichment analysis showed transcription factors, flower development, histone H3-K9 methylation, and plant hormone signal transduction were among the most significantly enriched GO terms and KEGG pathways. Small RNA analysis was also performed on the pistils from normal male and the male-to-hermaphrodite sex reversal flowers. Our result showed the 24 nt small RNAs were the most abundant in the pistils from both normal and sex reversal flowers, followed by 21 nt small RNAs. We detected expression of 40 plant-conserved miRNAs and 14 papaya-specific miRNAs in the pistils from one or both normal and sex reversal flowers. Sixteen miRNAs exhibited high-expression level and ten of them showed differential expression between the normal male and the male-to-hermaphrodite sex reversal flowers. Our results suggested the male-to-hermaphrodite sex reversal was likely caused by silencing the gynoecium suppression function on the sex determination pathway through epigenetic modification.
KeywordsCarica papaya Sex determination Sex reversal Differential gene expression Small RNA
This work was supported by the grant 2015 N20002-1 from the Department of Science and Technology in Fujian Province and startup fund from Fujian Agriculture and Forestry University.
Data archiving statement
All the sequence data reported here are archived and publicly available at the National Center for Biotechnology Information (NCBI; http://www.ncbi.nlm.nih.gov/). The RNA-Seq sequences can be accessed through NCBI SRA database under SRA ID SRP075300. The small RNA sequences can be accessed through NCBI SRA database under SRA ID SRP075300.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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