title: AINTEGUMENTA and the D-type cyclin CYCD3;1 independently contribute to petal size control in Arabidopsis: evidence for organ size compensation being an emergent rather than a determined property.
abstract: Plant lateral aerial organ (LAO) growth is determined by the number and size of cells comprising the organ. Genetic alteration of one parameter is often accompanied by changes in the other, such that the overall effect on final LAO size is minimized, suggested to be caused by an active organ level 'compensation mechanism'. For example, the aintegumenta (ant) mutant exhibits reduced cell number but increased cell size in LAOs. The ANT transcription factor regulates the duration of the cell division phase of LAO growth, and its ectopic expression is correlated with increased levels of the cell cycle regulator CYCD3;1. This has previously led to the suggestion that ANT regulates CYCD3;1. It is shown here that while ANT is required for normal cell proliferation in petals, CYCD3;1 is not, suggesting that ANT does not regulate CYCD3;1 during petal growth. Moreover CYCD3;1 expression was similar in wild-type and ant-9 flowers. In contrast to the compensatory changes between cell size and number in ant mutants, cycd3;1 mutants show increased petal cell size unaccompanied by changes in cell number, leading to larger organs. However, loss of CYCD3;1 in the ant-9 mutant background leads to a phenotype consistent with compensation mechanisms. These apparently arbitrary examples of compensation are reconciled through a model of LAO growth in which distinct phases of division and cell expansion occupy differing lengths of a defined overall growth window. This leads to the proposal that many observations of 'compensation mechanisms' might alternatively be more simply explained as emergent properties of LAO development.
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK.
authors.forename: Ricardo S
authors.initials: RS
authors.lastname: Randall
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK.
authors.forename: Emily
authors.initials: E
authors.lastname: Sornay
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK.
authors.forename: Walter
authors.initials: W
authors.lastname: Dewitte
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK murrayja1@cardiff.ac.uk.
authors.forename: James A H
authors.initials: JA
authors.lastname: Murray
mesh_terms: D017360:Arabidopsis / Q000033:anatomy & histology* / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001483:Base Sequence; D048429:Cell Size; D016213:Cyclins / Q000378:metabolism*; D035264:Flowers / Q000033:anatomy & histology* / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009929:Organ Size / Q000235:genetics; D010641:Phenotype; D011003:Ploidies; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: C099055:AINTEGUMENTA protein, Arabidopsis; D029681:Arabidopsis Proteins; C511744:CYCD3;1 protein, Arabidopsis; D016213:Cyclins; D012333:RNA, Messenger; D014157:Transcription Factors
keywords: AINTEGUMENTA; compensation mechanism; cyclin D; endoreduplication; organ size; petal growth.