Key Genes Behind Flower Petal Formation in Hollyhocks Revealed

Greg Howard
15th June, 2024

Key Genes Behind Flower Petal Formation in Hollyhocks Revealed

Image Source: Natural Science News, 2024

Key Findings

  • The study focused on the molecular mechanisms behind double-petal formation in hollyhock flowers, conducted by Sichuan Agricultural University
  • Researchers identified 3,212 genes that were differently expressed between normal petals and stamen petaloid petals
  • Key genes involved in plant hormone pathways and 56 important transcription factors were linked to the transformation of stamens into petal-like structures
Understanding the molecular mechanisms behind the formation of double-petal flowers in Alcea rosea L. has significant implications for horticulture and plant breeding. Alcea rosea, commonly known as hollyhock, is a traditional flower with a long cultivation history, extensively grown in China for its aesthetic appeal. Double-petal hollyhock flowers, characterized by the transformation of stamens into petal-like structures, are particularly valued for their enhanced beauty. However, the molecular basis of this transformation has remained largely unclear. A recent study conducted by researchers at Sichuan Agricultural University aims to elucidate these mechanisms through comparative transcriptomic analysis[1]. The study identified 3,212 differentially expressed genes (DEGs) between normal petals and stamen petaloid petals in A. rosea. These DEGs were further analyzed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. The findings revealed that numerous DEGs were involved in plant hormone synthesis and signal transduction pathways, such as auxin, cytokinin, gibberellin, abscisic acid, ethylene, brassinosteroid, jasmonic acid, and salicylic acid. Additionally, 56 key transcription factors, including MADS-box, bHLH, GRAS, and HSF, were identified as being significantly associated with stamen petaloid formation. The identification of these DEGs and transcription factors provides crucial insights into the regulatory pathways underlying the stamen-to-petal transformation. This discovery is consistent with previous studies on other plant species that have shown the involvement of hormone signaling pathways and transcription factors in similar floral transformations. For instance, in double-flower loquat (Eriobotrya japonica), the downregulation of a C-class floral homeotic gene, AGAMOUS ortholog (EjAG), was associated with the transformation of stamens into petals[2]. Similarly, in Lagerstroemia speciosa, the expression profiles of floral homeotic genes such as MADS16, AP2, SOC1, and AG were conserved across developmental stages but differed significantly between single- and double-flower phenotypes[3]. The current study on A. rosea builds upon these findings by expanding the understanding of the molecular mechanisms involved in stamen petaloid formation. The identification of DEGs related to hormone signaling pathways aligns with the observation in double-flower loquat, where the concentrations of hormones like auxin, gibberellin A, and cytokinin were found to be elevated during the petaloid stamen stage, while abscisic acid levels remained low[2]. This suggests a conserved role of hormone signaling in regulating floral organ identity across different plant species. Moreover, the study's focus on transcription factors such as MADS-box proteins is particularly noteworthy. MADS-box genes are well-known regulators of flower development and have been implicated in the control of floral organ identity in various plants. The robust transcriptional regulation observed in A. rosea is reminiscent of the regulatory mechanisms deduced in Lagerstroemia speciosa, where co-expressed genes with floral homeotic genes as hubs were identified[3]. This highlights the potential for cross-species comparisons to uncover common regulatory networks governing floral organ transformation. In addition to hormone signaling and transcription factors, the study also sheds light on the potential involvement of other pathways and mechanisms in stamen petaloid formation. For example, the prolonged petal initiation phase observed in Impatiens balsamina due to limiting amounts of a leaf-derived signal suggests a continuous and quantitative role for such signals in flower development[4]. While the specific nature of these signals in A. rosea remains to be determined, the study's findings provide a valuable starting point for further investigations into the complex interplay of genetic and environmental factors in floral organ identity. Overall, the identification of key DEGs and transcription factors in A. rosea offers important clues for understanding the molecular basis of stamen petaloid formation. These insights not only enhance our knowledge of floral development but also provide valuable information for molecular plant breeding. By leveraging these findings, researchers and breeders can develop new strategies to cultivate double-petal flowers with desired aesthetic and horticultural traits.

GeneticsBiochemPlant Science

References

Main Study

1) Transcriptomics analyses reveal the key genes involved in stamen petaloid formation in Alcea rosea L.

Published 14th June, 2024

https://doi.org/10.1186/s12870-024-05263-6

Related Studies

2) Homeotic transformation from stamen to petal in Eriobotrya japonica is associated with hormone signal transduction and reduction of the transcriptional activity of EjAG.

https://doi.org/10.1111/ppl.13029

3) Transcriptome analysis during floral organ development provides insights into stamen petaloidy in Lagerstroemia speciosa.

https://doi.org/10.1016/j.plaphy.2019.08.012

4) A leaf-derived signal is a quantitative determinant of floral form in Impatiens.

Journal: The Plant cell, Issue: Vol 12, Issue 10, Oct 2000


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