Floral Development Stage-Specific Transcriptomic Analysis Reveals the Formation Mechanism of Different Shapes of Ray Florets in Chrysanthemum

Abstract

The formation mechanism of different ray floret shapes of chrysanthemum (Chrysanthemum × morifolium) remains elusive due to its complex genetic background. C. vestitum, with the basic ray floret shapes of the flat, spoon, and tubular types, is considered a model material for studying ray floret morphogenesis. In this study, the flat and tubular type lines of C. vestitum at specific stages were used to investigate the key genes that regulate morphological differences in ray florets. We found that the expression levels of genes related to auxin synthesis, transport, and response were generally higher in the tubular type than in the flat type. CvARF3 was highly expressed in the flat type, while CvARF5 and CvARF6 were highly expressed in the tubular type. Additionally, the transcription levels of Class B and E genes closely related to petal development, including CvPI, CvAP3, Cvdefh21, CvSEP3, and CvCDM77, were expressed at higher levels in the tubular type than the flat type. Based on the results, it is proposed that auxin plays a key role in the development of ray florets, and auxin-related genes, especially CvARFs, may be key genes to control the morphological difference of ray florets. Simultaneously, MADS-box genes are involved in the co-regulation of ray floret morphogenesis. The results provide novel insights into the molecular mechanism of different petal type formation and lay a theoretical foundation for the directional breeding of petal type in chrysanthemums.

cla-miR164-NO APICAL MERISTEM (ClNAM) regulates the inflorescence architecture development of Chrysanthemum lavandulifolium

“…It has been shown that miRNA164 acts in conjunction with NAM/CUC as a homeostatic mechanism to regulate auxin signaling [ 27 , 29 , 30 ], while the localized enrichment of auxin is essential for floret patterning in Asteraceae [ 31 ]. In addition, auxin also has a regulatory role in the corolla morphology of ray floret in chrysanthemums [ 32 , 33 ]. In the present study, many differential expressions of auxin transporter proteins and auxin response factors were found in the OE- ClNAM lines, suggesting that cla-miR164- ClNAM may affect inflorescence architectures in chrysanthemums by regulating auxin signaling ( Fig.…”

Morphological Characteristics and Expression Patterns of CmCYC2c of Different Flower Shapes in Chrysanthemum morifolium

“…To clarify the morphological differences among various inflorescence and petal forms, a total of 12 chrysanthemum cultivars in five categories were observed at the full-bloom stage. As mentioned above, the classification of petal types is often based on the CTMD [9,10]. Generally speaking, the larger the merged degree, the more tubular the petals and the smaller the merged degree, the flatter the petals [9].…”

“…Moreover, the expression patterns of essential candidate genes, such as ClPIN1, ClARF5, CmYAB1, and CmCYC2s etc., were verified by RT-PCR and RNA in situ hybridization [14][15][16]. In recent years, the CYC-like TCP domain proteins have become a research hotspot for floret development in Asteraceae [10]. The CYC group experienced repetition and generated three main groups: CYC1, CYC2, and CYC3 [17].…”

“…According to the CTMD, ray florets are divided into three main types: flat, spoon, and tubular [8]. Other complex petals are formed based on these three basic shapes, such as those with irregular edges and/or appendages of the ray floret corolla which, in turn, leads to various flower forms in chrysanthemums [2,10]. Due to the diverse petal types and rich colors of chrysanthemums, many countries have established classification standards for chrysanthemums [11].…”