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

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.Electronic supplementary materialThe online version of this article (10.1186/s12870-018-1562-4) contains supplementary material, which is available to authorized users.

Differentially Expressed Genes between Carrot Petaloid Cytoplasmic Male Sterile and Maintainer during Floral Development

“…CvPI is essential for the specification of petal and stamen identity in Calluna vulgaris , and its reduced gene expression has been shown to result in the transition of petals into sepals 35 . In a homeotic mutant of Petrocosmea (Gesneriaceae), the dosage imbalance of B- and C-class genes—due to the upregulation of the two B-class genes DEFICIENS2 ( DEF2 ) and GLOBOSA ( GLO ) and the downregulation of the C-class gene PLE —caused the formation of petaloid stamens 36 . In rose ( Rosa hybrida ), suppression of the expression of RhAG increased the number of petals through the conversion of stamen petaloidy 37 .…”

Sexual types of flowers morphology inHeracleum sibiricum(Apiaceae)

“…Numerous next studies [17,18] found that the reduction of anthers and pollen at an early stage of flower development is more detrimental to the size of the corolla of pistillate flowers in gynodioecious species compare with their degeneration at later stages. Additional confirmation of the mutual influence of the forming petals and stamens in the flower was convincingly demonstrated by ABC, and later by ABCDE, a molecular biological model of flower development [20]. According to the ABCDE model, the development of the calyx, corolla, androecium and gynoecium in the flowers is determined by genes belonging to the five classes (A, B, C, D, and E).…”

“…According to the ABCDE model, the development of the calyx, corolla, androecium and gynoecium in the flowers is determined by genes belonging to the five classes (A, B, C, D, and E). At the same time, it has been shown that the products of the A + B + E genes are necessary for the formation of petals, and B + C + E for stamens [20]. Thus, there are at least two groups of genes (B and E) that determine the development of petals and stamens.…”

912. Petrocosmea Thermopuncta

“…‘Asa Blue’ (itself a cross between Petrocosmea flaccida and P. nervosa ) and P. chrysotricha raised by the American breeder Tim Tuttle. A study of more than 1500 flowers obtained from plants of P. glabristoma × P. sericea found 125 atypical flowers (Liu et al ., ). The authors concluded that imbalance between B‐ and C‐class genes caused petaloid stamen formation.…”