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

Zhao-Jun Pan,Hao-Chun Hsu,Tsun-Ying Chen,Chun-Neng Wang,Shih-Long Tu,Wen-Hsi Kuo,Yu-An Shih,Ya-Chi Nien,Wen-Dar Lin,Jen-Chih Chen

doi:10.3390/ijms23042073

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.

Highlights

Since we identified DV differentially expressed genes (DV-DEGs) involved in the auxin pathway at the key bud stage when speciosa have been identified as CYCLOIDEA (SsCYC) was highly expressed, we tested whether transient over-expression of SsCYC can regulate these DV-DEGs in petal protoplasts
Since we identified DV-DEGs involved in the auxin pathway at the key bud stage when SsCYC was highly expressed, we tested whether transient over-expression of SsCYC can regulate thesehomeostasis, DV-DEGs in auxin petal protoplasts
Our transcriptomic analysis major auxin signaling pathway which are dorsally highly expressed, and this analysis was associated with amajor longerauxin dorsalsignaling tube length

Summary

Introduction

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. The corolla exhibits an asymmetrical dorsal–ventral purple pigmentation pattern, in which dark spots or stripes are present on the inner surface of the ventral corolla tube, which likely serve as a nectar guide for visiting insects These pollination-related traits such as dorsal–ventral petal size, petal shape, and pigmentation differences in the corolla appear to correlate with the development of floral zygomorphy of S. speciosa

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Conclusion