Abstract
Main conclusionDuplicated petunia clade-VISPLgenes differentially promote the timing of inflorescence and flower development, and leaf initiation rate.The timing of plant reproduction relative to favorable environmental conditions is a critical component of plant fitness, and is often associated with variation in plant architecture and habit. Recent studies have shown that overexpression of the microRNA miR156 in distantly related annual species results in plants with perennial characteristics, including late flowering, weak apical dominance, and abundant leaf production. These phenotypes are largely mediated through the negative regulation of a subset of genes belonging to the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) family of transcription factors. In order to determine how and to what extent paralogous SPL genes have partitioned their roles in plant growth and development, we functionally characterized petunia clade-VI SPL genes under different environmental conditions. Our results demonstrate that PhSBP1and PhSBP2 differentially promote discrete stages of the reproductive transition, and that PhSBP1, and possibly PhCNR, accelerates leaf initiation rate. In contrast to the closest homologs in annual Arabidopsis thaliana and Mimulus guttatus, PhSBP1 and PhSBP2 transcription is not mediated by the gibberellic acid pathway, but is positively correlated with photoperiod and developmental age. The developmental functions of clade-VI SPL genes have, thus, evolved following both gene duplication and speciation within the core eudicots, likely through differential regulation and incomplete sub-functionalization.Electronic supplementary materialThe online version of this article (doi:10.1007/s00425-015-2413-2) contains supplementary material, which is available to authorized users.
Highlights
Variation in plant form results largely from the differential timing of developmental phase transitions that can occur gradually or rapidly in response to both endogenous and exogenous signalsPlanta (2016) 243:429–440(Poethig 2003; Baurle and Dean 2006)
Our study demonstrates that two petunia clade-VI SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes, PhSBP1 and PhSBP2, have evolved in function following their duplication at the base of core eudicots
The effects of gene silencing on development are consistent with PhSBP1 promoting inflorescence development, flower emergence, and leaf initiation in wild type petunias
Summary
Variation in plant form results largely from the differential timing of developmental phase transitions that can occur gradually (e.g., leaf size) or rapidly (e.g., flowering) in response to both endogenous and exogenous signalsPlanta (2016) 243:429–440(Poethig 2003; Baurle and Dean 2006). Some genes involved in differentiation are unaffected by shoot growth An example of the latter are many genes involved in flowering time that have no effect on the rate of leaf initiation. Mutations in these genes result in early- or late flowering, and cause a concomitant decrease or increase of leaves, respectively (Koorneef et al 1991; Haselhorst et al 2011). Understanding to what extent genes involved in phase change can be uncoupled from genes involved in shoot growth under different environmental conditions is a key question in plant developmental biology (Poethig 2003)
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