BACKGROUND: Understanding the mode and mechanisms of the evolution of the angiosperm flower is a long-standing and central problem of evolutionary biology and botany. It has essentially remained unsolved, however. In contrast, considerable progress has recently been made in our understanding of the genetic basis of flower development in some extant model species. The knowledge that accumulated this way has been pulled together in two major hypotheses, termed the 'ABC model' and the 'floral quartet model'. These models explain how the identity of the different types of floral organs is specified during flower development by homeotic selector genes encoding transcription factors. SCOPE: We intend to explain how the 'ABC model' and the 'floral quartet model' are now guiding investigations that help to understand the origin and diversification of the angiosperm flower. CONCLUSIONS: Investigation of orthologues of class B and class C floral homeotic genes in gymnosperms suggest that bisexuality was one of the first innovations during the origin of the flower. The transition from dimer to tetramer formation of floral homeotic proteins after establishment of class E proteins may have increased cooperativity of DNA binding of the transcription factors controlling reproductive growth. That way, we hypothesize, better 'developmental switches' originated that facilitated the early evolution of the flower. Expression studies of ABC genes in basally diverging angiosperm lineages, monocots and basal eudicots suggest that the 'classical' ABC system known from core eudicots originated from a more fuzzy system with fading borders of gene expression and gradual transitions in organ identity, by sharpening of ABC gene expression domains and organ borders. Shifting boundaries of ABC gene expression may have contributed to the diversification of the angiosperm flower many times independently, as may have changes in interactions between ABC genes and their target genes.
BACKGROUND: Understanding the mode and mechanisms of the evolution of the angiosperm flower is a long-standing and central problem of evolutionary biology and botany. It has essentially remained unsolved, however. In contrast, considerable progress has recently been made in our understanding of the genetic basis of flower development in some extant model species. The knowledge that accumulated this way has been pulled together in two major hypotheses, termed the 'ABC model' and the 'floral quartet model'. These models explain how the identity of the different types of floral organs is specified during flower development by homeotic selector genes encoding transcription factors. SCOPE: We intend to explain how the 'ABC model' and the 'floral quartet model' are now guiding investigations that help to understand the origin and diversification of the angiosperm flower. CONCLUSIONS: Investigation of orthologues of class B and class C floral homeotic genes in gymnosperms suggest that bisexuality was one of the first innovations during the origin of the flower. The transition from dimer to tetramer formation of floral homeotic proteins after establishment of class E proteins may have increased cooperativity of DNA binding of the transcription factors controlling reproductive growth. That way, we hypothesize, better 'developmental switches' originated that facilitated the early evolution of the flower. Expression studies of ABC genes in basally diverging angiosperm lineages, monocots and basal eudicots suggest that the 'classical' ABC system known from core eudicots originated from a more fuzzy system with fading borders of gene expression and gradual transitions in organ identity, by sharpening of ABC gene expression domains and organ borders. Shifting boundaries of ABC gene expression may have contributed to the diversification of the angiosperm flower many times independently, as may have changes in interactions between ABC genes and their target genes.
Authors: T J Barkman; G Chenery; J R McNeal; J Lyons-Weiler; W J Ellisens; G Moore; A D Wolfe; C W dePamphilis Journal: Proc Natl Acad Sci U S A Date: 2000-11-21 Impact factor: 11.205
Authors: André S Chanderbali; Mi-Jeong Yoo; Laura M Zahn; Samuel F Brockington; P Kerr Wall; Matthew A Gitzendanner; Victor A Albert; James Leebens-Mack; Naomi S Altman; Hong Ma; Claude W dePamphilis; Douglas E Soltis; Pamela S Soltis Journal: Proc Natl Acad Sci U S A Date: 2010-12-13 Impact factor: 11.205
Authors: Elena R Alvarez-Buylla; Mariana Benítez; Adriana Corvera-Poiré; Alvaro Chaos Cador; Stefan de Folter; Alicia Gamboa de Buen; Adriana Garay-Arroyo; Berenice García-Ponce; Fabiola Jaimes-Miranda; Rigoberto V Pérez-Ruiz; Alma Piñeyro-Nelson; Yara E Sánchez-Corrales Journal: Arabidopsis Book Date: 2010-03-23
Authors: José Díaz-Riquelme; Diego Lijavetzky; José M Martínez-Zapater; María José Carmona Journal: Plant Physiol Date: 2008-11-07 Impact factor: 8.340
Authors: Samuel E Wuest; Diarmuid S O'Maoileidigh; Liina Rae; Kamila Kwasniewska; Andrea Raganelli; Katarzyna Hanczaryk; Amanda J Lohan; Brendan Loftus; Emmanuelle Graciet; Frank Wellmer Journal: Proc Natl Acad Sci U S A Date: 2012-07-30 Impact factor: 11.205