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.
Flowering time is strictly controlled by a combination of internal and external signals that match seed set with favorable environmental conditions. In the model plant species Arabidopsis thaliana (Brassicaceae), many of the genes underlying development and evolution of flowering have been discovered. However, much remains unknown about how conserved the flowering gene networks are in plants with different growth habits, gene duplication histories, and distributions. Here we functionally characterize three homologs of the flowering gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) in the short-lived perennial Petunia hybrida (petunia, Solanaceae). Similar to A. thaliana soc1 mutants, co-silencing of duplicated petunia SOC1-like genes results in late flowering. This phenotype is most severe when all three SOC1-like genes are silenced. Furthermore, expression levels of the SOC1-like genes UNSHAVEN (UNS) and FLORAL BINDING PROTEIN 21 (FBP21), but not FBP28, are positively correlated with developmental age. In contrast to A. thaliana, petunia SOC1-like gene expression did not increase with longer photoperiods, and FBP28 transcripts were actually more abundant under short days. Despite evidence of functional redundancy, differential spatio-temporal expression data suggest that SOC1-like genes might fine-tune petunia flowering in response to photoperiod and developmental stage. This likely resulted from modification of SOC1-like gene regulatory elements following recent duplication, and is a possible mechanism to ensure flowering under both inductive and non-inductive photoperiods.
Premise of the study: Large scale projects such as NEON are collecting ecological data on entire biomes to track and understand plant responses to climate change. NEON provides an opportunity for researchers to launch community transcriptomic projects that ask integrative questions in ecology and evolution. We conducted a pilot study to investigate the challenges of collecting RNA-seq data from phylogenetically diverse NEON plant communities, including species with diploid and polyploid genomes.• Methods: We used Illumina NextSeq to generate >20 Gb of RNA-seq for each of 24 vascular plant species representing 12 genera and 9 families at the Harvard Forest NEON site. Each species was sampled twice, in July and August 2016. We used Transrate, BUSCO, and GO analyses to assess transcriptome quality and content. • Results: We obtained nearly 650 Gb of RNA-seq data that assembled into more than 755,000 translated protein sequences across the 24 species. We observed only modest differences in assembly quality scores across a range of k-mer values. On average, transcriptomes contained hits to >70% of loci in the BUSCO
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