Differential gene expression among three sex types reveals a MALE STERILITY 1 (CpMS1) for sex differentiation in papaya

Abstract

BackgroundCarica papaya is a trioecious plant species with a genetic sex-determination system defined by sex chromosomes. Under unfavorable environmental conditions male and hermaphrodite exhibit sex-reversal. Previous genomic research revealed few candidate genes for sex differentiation in this species. Nevertheless, more analysis is still needed to identify the mechanism responsible for sex flower organ development in papaya.ResultsThe aim of this study was to identify differentially expressed genes among male, female and hermaphrodite flowers in papaya during early (pre-meiosis) and later (post-meiosis) stages of flower development. RNA-seq was used to evaluate the expression of differentially expressed genes and RT-qPCR was used to verify the results. Putative functions of these genes were analyzed based on their homology with orthologs in other plant species and their expression patterns. We identified a Male Sterility 1 gene (CpMS1) highly up-regulated in male and hermaphrodite flower buds compared to female flower buds, which expresses in small male flower buds (3–8 mm), and that might be playing an important role in male flower organ development due to its homology to MS1 genes previously identified in other plants. This is the first study in which the sex-biased expression of genes related to tapetum development in the anther developmental pathway is being reported in papaya. Besides important transcription factors related to flower organ development and flowering time regulation, we identified differential expression of genes that are known to participate in ABA, ROS and auxin signaling pathways (ABA-8-hydroxylases, AIL5, UPBEAT 1, VAN3-binding protein).ConclusionsCpMS1 was expressed in papaya male and hermaphrodite flowers at early stages, suggesting that this gene might participate in male flower organ development processes, nevertheless, this gene cannot be considered a sex-determination gene. Due to its homology with other plant MS1 proteins and its expression pattern, we hypothesize that this gene participates in anther development processes, like tapetum and pollen development, downstream gender specification. Further gene functional characterization studies in papaya are required to confirm this hypothesis. The role of ABA and ROS signaling pathways in papaya flower development needs to be further explored as well.

Comparative proteomic analysis of papaya bud flowers reveals metabolic signatures and pathways driving hermaphrodite development

“…Although transcriptome analyses focusing on the sexual differentiation of papaya have revealed several genes related to the biosynthesis of plant hormones and ABA, ROS, and auxin signaling pathways, most of the DAPs observed between the sexes in the present study were involved in carbohydrate metabolism, phenylpropanoid biosynthesis, and sporopollenin biosynthesis 13 , 32 , 33 . Furthermore, the genes encoding these proteins were all mapped to autosomal chromosomes or the autosomal region of chromosome 1.…”

Transposon insertions regulate genome‐wide allele‐specific expression and underpin flower colour variations in apple (Malus spp.)

“…ASE analysis has several advantages over differential gene expression (DGE) analysis. The latter has been widely used to identify genes differentially expressed between different tissues of the same genotype, between the same tissues of different genotypes, or the same tissue across time courses (Klumb et al ., 2020; Nishitani et al ., 2020; Wang et al ., 2020; Zerpa‐Catanho et al ., 2019). However, DGE does not address allele specificity.…”

Integrative Analyses of Transcriptomics and Metabolomics in Sex Differentiation of Mulberry Flowers

“…LRR-RLKs act upon the substrates which control floral organ abscission ( Cho et al, 2008 ), and some of them were found to be involved in the floral growth and development of S. japonicus ( Li J. et al, 2019 ). In Carica papaya , two LRR-RLK genes were upregulated in its female buds and may be involved in that plant’s sex differentiation ( Zerpa-Catanho et al, 2019 ). The C2H2 TFs have been previously documented to play important roles in various processes during plant development, including sex determination.…”