Dosage imbalance of B- and C-class genes causes petaloid-stamen relating to F1 hybrid variation

Jing Liu,Yang Dong,Yin-Zheng Wang,Xia Yang,Chao-Qun Li

doi:10.1186/s12870-018-1562-4

Jing Liu, Yang Dong + Show 3 more

Open Access

https://doi.org/10.1186/s12870-018-1562-4

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Abstract

BackgroundGreat advances have been achieved in our understanding of flower development and evolution since the establishment of the ABC model. However, it remains a challenge to define the exact context of organ identity in the component interactions of the ABC model.ResultsThrough hybridization, we detected a homeotic mutant in Petrocosmea (Gesneriaceae) uniquely displayed by the ‘petaloid-stamen’ in the third whorl with petal identity. Comparative Real-time PCR analyses demonstrate that both two B-class genes DEF2 and GLO are excessively expressed while the transcripts of the C-class gene PLE are reduced in the third floral whorl in the mutant compared to that in the wild-type F1 hybrids. Further allele-specific expression (ASE) analyses indicate that an allele-specific change in PgPLE might be responsible for up-regulation of both B-class genes and down-regulation of the C-class gene in the petaloid-stamen mutants.ConclusionsOur findings suggest that the petaloid-stamen is consequent upon an evident dosage imbalance between B- and C-class products that is probably triggered by a cis-regulatory change. In addition, the genetic pathway for the floral organ identity might be in parallel with that for the floral symmetry. The extreme variation in hybrids further suggests that interspecific hybridization may represent a major factor for evolutionary innovation and diversification in plants.

Highlights

Great advances have been achieved in our understanding of flower development and evolution since the establishment of the ABC model
The canonical flower development model, known as the ABC model, was proposed based on homeotic mutants which refer to the transformation of the organ identity from one to another at particular whorl produced in Arabidopsis thaliana and Antirrhinum majus [1]
The petal-like organs corresponding to the dorsally and laterally aborted and ventrally fertile stamens of wild-type F1 hybrids increase in size, indicating that the floral symmetry of the mutant is unchanged in the third whorl (Fig. 1d, f )

Summary

Introduction

Great advances have been achieved in our understanding of flower development and evolution since the establishment of the ABC model. The canonical flower development model, known as the ABC model, was proposed based on homeotic mutants which refer to the transformation of the organ identity from one to another at particular whorl produced in Arabidopsis thaliana and Antirrhinum majus [1]. The petalody or petaloid-stamen of the third floral whorl is more complicated than the situation of the first whorl because it is potentially related to both B- and C-class gene activities. Homeotic mutants in A. thaliana and A. majus play an important role in the intersection of genetic and development as the basis for the establishment of the classical ABC model. Genetic and molecular studies of the petaloid-stamen mutant in non-model organisms would provide a new insight into the genetic and evolutionary origin of particular floral organ types or novel mechanism underlying specific phenomena that is not present in current model systems

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