Abstract
The molecular mechanism of sex development and differentiation in the economically important dioecious fruit tree, red bayberry (Morella rubra), was revealed using next-generation transcriptome sequencing (NGS), and comparative analyses were used to identify differentially expressed genes (DEGs) in female and male flower buds. A total of 7029 of these DEGs were identified at two early development stages. KEGG pathway enrichment analysis revealed that plant hormone signal transduction was significantly overrepresented, and 91 genes related to hormones were identified. An analysis of 7029 DEGs revealed 161 hormone-related genes, with the 42 related to auxin and 26 related to ethylene being the most highly represented. A total of 62 genes were significantly up-regulated in females and 29 were in males, with 18 of them specifically expressed in females and 10 in males. A total of 415 transcription factors were identified, with 129 genes up-regulated in females and 53 in males. Moreover, 38 had female-specific expression and 18 had male-specific expression. Using weighted gene co-expression network analysis (WGCNA), two modules were found to be associated with sexual type. In the module coded light-green, there were five genes related to hormones, one to flower development and ten transcription factors with four genes specifically expressed in the males and four in females. The hub gene in the light-green module is MR0TCONS_00017483.1 (ACO), which is involved in ethylene biosynthesis and had male-specific expression. Among the transcription factors, three of the four male-specific expressed genes involved in flavonoid biosynthesis, including the MYB gene MR1TCONS_00020658.1 and two BHLH genes, MR6G001563.1 and MR8G020751.1, played important roles in male floral differentiation. In the dark-cyan module, six hormone-related genes, five transcription factors and three flower development genes were identified with the hub gene MR1G019545.1 (ETR1), which participates in the ethylene signaling pathway, and MR4G023618.1, which encodes the C3H zinc finger transcription factor. These results indicate that ethylene is the key hormone that interacts with other hormones and transcription factors to regulate sex differentiation in the red bayberry, which also provides new insights into the mechanism of sex determination and differentiation in the red bayberry.
Highlights
A principal component analysis (PCA) based on FPKM values separated the samples into four distinct groups, with each sample making a separate group with its replicates (Figure S1)
There were three genes related to flower development: MR8G010076.1, which encodes homologs of AtUGT87A2 (AT2G30140), which regulate flowering time via FLOWERING LOCUS C; MR7G011514.1 the homolog of Arabidopsis AtVRN1; and the MR8G001578.1 homolog in Arabidopsis is AtSPL14 (AT1G20980). These results showed that ethylene biosynthesis and signaling pathways may play vital roles in sex differentiation and flower development, with the transcription factor playing vital roles in regulating flower buds
We found 8889 differentially expressed genes (DEGs) in pair-wise analyses of F1 vs. F0, M1 vs. M0, M0 vs. F0 and M1 vs. F1 that may be related to sex differentiation and flower development
Summary
The evolution of sex differentiation is an interesting topic because it is important to strategies for outbreeding, the prevention of inbreeding depression and a vital source. Horticulturae 2022, 8, 183 of genetic variation. About 10% of flowering plants have separate unisexual flowers in different individuals (dioecy) or in the same individual (monoecy) [1]. For the mechanisms of unisexual flower development, two categories of unisexual flowers have been defined [2,3]. In type I, bisexual flowers become unisexual through the termination of the development of the androecium or gynoecium. The sex differentiation occurs at the particular developmental stage when one of the reproductive organs is arrested. Flowers of type II are unisexual from inception, and sex differentiation occurs before the formation of female or male organ primordia [3]
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