Abstract
Petal expansion is the main process by which flower opening occurs in roses (Rosa chinensis). Although the regulation of leaf expansion has been extensively studied, little is known about the mechanisms controlling petal expansion. The regulation of leaf dorsoventral (adaxial–abaxial) polarity is important for blade expansion and morphogenesis, but the mechanisms involved adaxial–abaxial regulation in petals are unknown. We found that auxin, a key hormonal regulator of leaf adaxial–abaxial patterning, is unevenly distributed in rose petals. The transcriptomes of the adaxial and abaxial petal tissues were sequenced at three developmental stages during flower opening. Genes that were differentially expressed between the two tissues were filtered for those known to be involved in petal expansion and phytohormone biosynthesis, transport, and signaling, revealing potential roles in petal expansion, especially auxin pathway genes. Using a weighted gene coexpression network analysis (WGCNA), we identified two gene modules that may involve in adaxial–abaxial regulation, 21 and five hub genes have been found respectively. The qRT-PCR validation results were consistent with the RNA-seq data. Based on these findings, we propose a simple network of adaxial–abaxial-related genes that regulates petal expansion in R. chinensis “Old Blush.” For the first time, we report the adaxial–abaxial transcriptional changes that occur during petal expansion, providing a reference for the study of the regulation of polarity in plant development.
Highlights
Roses (Rosa sp.) are the world’s most popular cut flower and an important horticultural species (Krussmann, 1981; Debener and Linde, 2009)
Does adaxial–abaxial polarity participate in the regulation of petal expansion in roses? Is this process driven by auxin? Which genes are involved? In this study, we examined the distribution of auxin in the adaxial and abaxial layers of rose (R. chinensis “Old Blush”) petals during three stages of floral development, from the flower bud to senescence, using transcriptome sequencing and a weighted gene coexpression network analysis (WGCNA) in addition to the newly released genomic data for this cultivar
A microscopy observation revealed that the adaxial epidermal cells of “Old Blush” petals in all stages are conical papillate, whereas the abaxial epidermal cells are flat with irregular edges (Figure 1D)
Summary
Roses (Rosa sp.) are the world’s most popular cut flower and an important horticultural species (Krussmann, 1981; Debener and Linde, 2009). Flower organ differentiation is largely complete before the rosebud opens; the quality of the flower, Rose Petal Dorsoventral-Related Genes especially the petal shape and structure (van Doorn and Kamdee, 2014), is established during flower opening. The establishment of adaxial–abaxial polarity during the early stages of leaf development is an important process regulating leaf expansion, the molecular regulation of which has been examined in many previous studies (Braybrook and Kuhlemeier, 2010; Ishibashi et al, 2013). These findings can be used as references for the study of rose petal dorsiventrality
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