RESUMO
BACKGROUND: The ray floret shapes referred to as petal types on the chrysanthemum (Chrysanthemum × morifolium Ramat.) capitulum is extremely abundant, which is one of the most important ornamental traits of chrysanthemum. However, the regulatory mechanisms of different ray floret shapes are still unknown. C. vestitum is a major origin species of cultivated chrysanthemum and has flat, spoon, and tubular type of ray florets which are the three basic petal types of chrysanthemum. Therefore, it is an ideal model material for studying ray floret morphogenesis in chrysanthemum. Here, using morphological, gene expression and transcriptomic analyses of different ray floret types of C. vestitum, we explored the developmental processes and underlying regulatory networks of ray florets. RESULTS: The formation of the flat type was due to stagnation of its dorsal petal primordium, while the petal primordium of the tubular type had an intact ring shape. Morphological differences between the two ray floret types occurred during the initial stage with vigorous cell division. Analysis of genes related to flower development showed that CYCLOIDEA genes, including CYC2b, CYC2d, CYC2e, and CYC2f, were differentially expressed in different ray floret types, while the transcriptional levels of others, such as MADS-box genes, were not significantly different. Hormone-related genes, including SMALL AUXIN UPREGULATED RNA (SAUR), GRETCHEN HAGEN3 (GH3), GIBBERELLIN 2-BETA-DIOXYGENASE 1 (GA2OX1) and APETALA2/ETHYLENE RESPONSIVE FACTOR (AP2/ERF), were identified from 1532 differentially expressed genes (DEGs) in pairwise comparisons among the flat, spoon, and tubular types, with significantly higher expression in the tubular type than that in the flat type and potential involvement in the morphogenesis of different ray floret types. CONCLUSIONS: Our findings, together with the gene interactional relationships reported for Arabidopsis thaliana, suggest that hormone-related genes are highly expressed in the tubular type, promoting petal cell division and leading to the formation of a complete ring of the petal primordium. These results provide novel insights into the morphological variation of ray floret of chrysanthemum.
Assuntos
Chrysanthemum , Chrysanthemum/genética , Chrysanthemum/metabolismo , Flores/genética , Flores/metabolismo , Regulação da Expressão Gênica de Plantas , Morfogênese/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , TranscriptomaRESUMO
The diversity of form of the chrysanthemum flower makes this species an ideal model for studying petal morphogenesis, but as yet, the molecular mechanisms underlying petal shape development remain largely unexplored. Here, a floral mutant, which arose as a bud sport in a plant of the variety 'Anastasia Dark Green', and formed straight, rather than hooked petals, was subjected to both comparative morphological analysis and transcriptome profiling. The hooked petals only became discernible during a late stage of flower development. At the late stage of 'Anastasia Dark Green', genes related to chloroplast, hormone metabolism, cell wall and microtubules were active, as were cell division-promoting factors. Auxin concentration was significantly reduced, and a positive regulator of cell expansion was down-regulated. Two types of critical candidates, boundary genes and adaxial-abaxial regulators, were identified from 7937 differentially expressed genes in pairwise comparisons, which were up-regulated at the late stage in 'Anastasia Dark Green' and another two hooked varieties. Ectopic expression of a candidate abaxial gene, CmYAB1, in chrysanthemum led to changes in petal curvature and inflorescence morphology. Our findings provide new insights into the regulatory networks underlying chrysanthemum petal morphogenesis.
Assuntos
Chrysanthemum/genética , Flores/anatomia & histologia , Flores/genética , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos/químicaRESUMO
miR319 was the first plant miRNA discovered via forward genetic mutation screening. In this study, we found that miR319 family members had similar sequences but different expression patterns in Brassica campestris and Arabidopsis thaliana. RT-PCR analysis revealed that Bra-MIR319a and Bra-MIR319c had similar expression patterns and were widely expressed in plant development, whereas Bra-MIR319b could only be detected in stems. The overexpression of each Bra-MIR319 family member in Arabidopsis could inhibit cell division and function in leaf and petal morphogenesis. Bra-miR319a formed a new regulatory relationship after whole genome triplication, and Bra-MIR319a overexpressing in Arabidopsis led to the degradation of pollen content and affected the formation of intine, thereby causing pollen abortion. Our results suggest that Bra-MIR319 family members have functional similarity and difference in plant development.