Transcriptomic Analysis Suggests Auxin Regulation in Dorsal-Ventral Petal Asymmetry of Wild Progenitor Sinningia speciosa

Abstract

The establishment of dorsal–ventral (DV) petal asymmetry is accompanied by differential growth of DV petal size, shape, and color differences, which enhance ornamental values. Genes involved in flower symmetry in Sinningia speciosa have been identified as CYCLOIDEA (SsCYC), but which gene regulatory network (GRN) is associated with SsCYC to establish DV petal asymmetry is still unknown. To uncover the GRN of DV petal asymmetry, we identified 630 DV differentially expressed genes (DV-DEGs) from the RNA-Seq of dorsal and ventral petals in the wild progenitor, S. speciosa ‘ES’. Validated by qRT-PCR, genes in the auxin signaling transduction pathway, SsCYC, and a major regulator of anthocyanin biosynthesis were upregulated in dorsal petals. These genes correlated with a higher endogenous auxin level in dorsal petals, with longer tube length growth through cell expansion and a purple dorsal color. Over-expression of SsCYC in Nicotiana reduced petal size by regulating cell growth, suggesting that SsCYC also controls cell expansion. This suggests that auxin and SsCYC both regulate DV petal asymmetry. Transiently over-expressed SsCYC, however, could not activate most major auxin signaling genes, suggesting that SsCYC may not trigger auxin regulation. Whether auxin can activate SsCYC or whether they act independently to regulate DV petal asymmetry remains to be explored in the future.

Development of a petal protoplast transfection system for Sinningia speciosa

“…We developed the large‐scale procedures to reduce the processing time and labor required in situations where large quantities of RNA must be extracted from transfected protoplasts (e.g., for the analysis of the expression of numerous candidate genes or in transcriptome sequencing). For the small‐scale procedure, 1.5 g of fresh petals from 5–6 pre‐bloom flowers at floral bud stages 10–12 (FB10–12, at which the length of the corolla tube is 21–30 mm; Pan et al, 2022 ) were collected (Figure 1A ). For the large‐scale procedure, 4.5 g of fresh petals from 15 FB10–12 floral buds were used.…”

“…Protoplasts were not isolated from plants near the beginning or end of the flowering period. Petals of prebloom flowers at floral bud stages 10–12 (FB10–12) were freshly collected (Pan et al, 2022 ).…”

Genome-wide identification and characterization of TCP gene family in Dendrobium nobile and their role in perianth development

“…Chimeric repressor silencing technology (CRES-T) applies this phenomenon to produce novel floral traits in horticultural plants of high ornamental value ( Narumi et al., 2011 ; Ono et al., 2012 ; Zhang et al., 2021a ). Meanwhile, CYC/TB1 members play crucial roles in lateral branching ( Doebley et al., 1997 ; Aguilar-Martínez et al., 2007 ) and flower symmetry ( Preston et al., 2011 ; Zhao et al., 2018 ; Pan et al., 2022 ). Unlike the functions of Class II members, most Class I TCP members remain unclear and have mainly been characterized in model plants ( Viola et al., 2023 ).…”