Transcriptomic and hormone analyses reveal mechanisms underlying petal elongation in Chrysanthemum morifolium ‘Jinba’

Abstract

Auxin regulates chrysanthemum petal elongation by promoting cell elongation. Transcriptomic analysis shows that auxin signal transduction may connect with other transcription factors by TCPs to regulate chrysanthemum petal elongation. As an ornamental species, Chrysanthemum morifolium has high ornamental and economic value. Petal size is the primary factor that influences the ornamental value of chrysanthemum, but the mechanism underlying the development of C. morifolium petals remains unclear. In our study, we tracked the growth of petals and found that the basal region of 'Jinba' petals showed a higher elongation rate, exhibiting rapid cell elongation during petal growth. During petal elongation growth, auxin was demonstrated to promote cell elongation and an increase in cell numbers in the petal basal region. To further study the molecular mechanisms underlying petal growth, the RNA-seq (high-throughput cDNA sequencing) technique was employed. Four cDNA libraries were assembled from petals in the budding, bud breaking, early blooming and full blooming stages of 'Jinba' flower development. Analysis of differentially expressed genes (DEGs) showed that auxin was the most important regulator in controlling petal growth. The TEOSINTEBRANCHED 1, CYCLOIDEA and PCF transcription factor genes (TCPs), basic helix-loop-helix-encoding gene (bHLH), glutaredoxin-C (GRXC) and other zinc finger protein genes exhibited obvious up-regulation and might have significant effects on the growth of 'Jinba' petals. Given the interaction between these genes in Arabidopsis thaliana, we speculated that auxin signal transduction might exhibit a close relationship with transcription factors through TCPs. In summary, we present the first comprehensive transcriptomic and hormone analyses of C. morifolium petals. The results offer direction in identifying the mechanism underlying the development of chrysanthemum petals in the elongated phase and have great significance in improving the ornamental characteristics of C. morifolium via molecular breeding.

Comprehensive characterization of a floral mutant reveals the mechanism of hooked petal morphogenesis in Chrysanthemum morifolium

“…Taking advantage of next‐generation sequencing, a number of differentially expressed genes were identified from a pairwise comparison of ray florets and disc florets of chrysanthemum (Liu et al ., ). Our previous study showed that auxin and some key transcription factors were involved in the growth of chrysanthemum petals (Wang et al ., ). In addition, CYCLOIDEA ( CYC )‐like genes have been reported as being involved in the regulation of flower symmetry in Asteraceae species (Broholm et al ., ; Huang et al ., ; Juntheikki‐Palovaara et al ., ; Kim et al ., ).…”

Transcriptomic analysis of flower opening response to relatively low temperatures in Osmanthus fragrans

“…There are some reports on phytohormones that can affect the oral opening [19], and therefore, we explored the DEGs involved in eight phytohormone signal transduction pathways. The levels of endogenous AUX were much higher in the basal petals and application of exogenous indole-3-butyric acid (IBA) can enlarge the cell length in chrysanthemum [5]. Many unigenes involved in AUX signal transduction pathway were increasingly expressed with the ower opening of rose, suggesting that AUX signaling participated in petal development [37].…”

“…79 TFs which were divided into eight gene family (Fig. 6, Table S10) were selected for further analysis because they may be involved in petal cell expansion [5,37]. In the MYB TF family, only ve out of twenty genes (Unigene36971, CL242.Contig2, CL10695.Contig2, Unigene11061, and Unigene30676) were up-expressed under relatively low temperature.…”

“…Flower petals are the most important component of reproductive organs and play vital roles in attracting the suitable pollinator(s). Flower color, size, shape and appearance, which are determined by ower petal, are important traits appreciated by the breeders and consumers [5]. One of the traits, the size of ower petal is determined by cell division at early phases of petal growth and cell expansion at later stages of ower opening [6].…”

“…Phytohormones are the most important mediators regulating ower opening and could be affected by circadian factors or environmental factors. As far as the present researches are concerned, most of the phytohormones, such as auxin (AUX), gibberellin (GA), ethylene (ETH), brassinosteroid (BR), jasmonic acid (JA) and abscisic acid (ABA), are proven to affect ower opening [5,6,[20][21][22].…”