Decoding a unique double flower pattern in herbaceous peony: insight into proliferate flower bud development

Area of Science:

• Plant developmental biology
• Floral morphology and anatomy
• Molecular genetics of flower development

Background:

• Herbaceous peonies exhibit a proliferate flower pattern with high ornamental value.
• The complex, two-layered structure of proliferate flowers presents challenges in understanding their development.
• Previous research has not fully elucidated the developmental mechanisms behind proliferate flowers.

Purpose of the Study:

• To decode the developmental pattern of proliferate flowers in herbaceous peonies.
• To investigate the morphological and anatomical characteristics of pistils and stamens in proliferate flowers.
• To identify key genes involved in the development of proliferate flowers.

Main Methods:

• Floral differentiation was observed in single, double, and four proliferate flower varieties.
• Stereomicroscopy, paraffin sectioning, and free-hand sectioning were employed for morphological analysis.
• Quantitative reverse transcription PCR (qRT-PCR) was used to analyze the expression of floral development genes.

Main Results:

• Proliferate flowers develop in two stages: lower flower formation followed by upper flower differentiation from the pistil primordia.
• Upper flowers retain carpel characteristics and differentiate petals, stamens, and pistils.
• Classical ABCDE model genes (PlAP1, PlPl2, PlAP3, PlSEP1, PlSEP3) showed higher expression in proliferate flowers, while PlAG expression was significantly reduced.

Conclusions:

• Proliferate flowers are a specialized double flower type comprising distinct upper and lower floral components.
• Petaloid stamen variations in lower flowers are linked to cultivar diversity; pistil proliferation drives upper flower origin.
• Reduced expression of the C-class gene PlAG is implicated in the induction of proliferate flower development.