Project description:Perennial plants maintain their life span through several growth seasons. Arabis alpina serves as model Brassicaceae species to study perennial traits. A. alpina lateral stems have a proximal vegetative zone with a dormant bud zone, and a distal senescing seed-producing inflorescence zone. We addressed the questions of how this zonation is distinguished at the anatomical level, whether it is related to nutrient storage, and which signals affect the zonation. We found that the vegetative zone ehxibits secondary growth, which we termed the perennial growth zone (PZ). High-molecular weight carbon compounds accumulate there in cambium and cambium derivatives. Neither vernalization nor flowering were requirements for secondary growth and sequestration of storage compounds. The inflorescence zone with only primary growth, termed annual growth zone (AZ), or roots exhibited different storage characteristics. Following cytokinin application, cambium activity was enhanced and secondary phloem parenchyma was formed in the PZ and also in the AZ. In transcriptome analysis cytokinin-related genes represented enriched gene ontology terms and were expressed at higher level in PZ than AZ. Thus, A. alpina uses primarily the vegetative PZ for nutrient storage, coupled to cytokinin-promoted secondary growth. This finding lays a foundation for future studies addressing signals for perennial growth.
Project description:We compared gene expression in axillary buds from annual and biennial flowering raspberry to identify differentially expressed genes.
Project description:Genome-wide landscapes of transcription factor (TF) binding sites (BSs) diverge during evolution, conferring species-specific transcriptional patterns. The rate of divergence varies in different metazoan lineages but has not been widely studied in plants. We identified the BSs and assessed the effects on transcription of FLOWERING LOCUS C (FLC) and PERPETUAL FLOWERING 1 (PEP1), two orthologous MADS-box TFs that repress flowering and confer vernalization requirement in the Brassicaceae species Arabidopsis thaliana and Arabis alpina, respectively. We found the BSs that were conserved in both species, and that these contained a CArG-box that is recognised by MADS-box TFs. The CArG-box consensus at conserved BSs was extended compared to the core motif. By contrast, species-specific BSs usually lacked the CArG-box in the other species. Flowering-time genes were highly overrepresented among conserved targets and their CArG-boxes were widely conserved among Brassicaceae species. Cold-regulated genes (COR) were also overrepresented among targets, but the cognate BSs and the identity of the regulated genes were different in each species. In cold, COR gene transcript levels were increased in flc and pep1-1 mutants compared to wild-type and this correlated with reduced growth in pep1-1. Therefore FLC orthologs regulate a set of conserved target genes mainly involved in reproductive development and were later independently recruited to modulate stress responses in different Brassicaceae lineages. Analysis of TF BSs in these lineages thus distinguishes widely conserved targets representing the core function of the TF from those that were recruited later in evolution.
Project description:The annual cleistogamous herb Cardamine kokaiensis is an endemic plant along the Kokai River in Japan. We examined the differences in gene expression patterns among cleistogamous (CL), intermediate (INT), and chasmogamous (CH) flower by cross-species microarray analysis using an Arabidopsis thaliana Affymetrix high-density oligonucleotide microarray (GeneChip ATH1). We then discuss the molecular basis of the evolution of cleistogamy. Our results help to clarify the molecular basis of the evolution of plant mating systems that depend on environmental conditions. CITATION: Ecogenomics of cleistogamous and chasmogamous flowering: genome-wide gene expression patterns from cross-species microarray analysis in Cardamine kokaiensis (Brassicaceae); Journal of Ecology 2008; Shin-Ichi Morinaga, Atsushi J. Nagano, Saori Miyazaki, Minoru Kubo, Taku Demura, Hiroo Fukuda, Satoki Sakai, Mitsuyasu Hasebe Experiment Overall Design: gDNA hybridyzation data was used to calibration of cross-species microarray using Affymetrix ATH1. CH, INT, and CL flowers of C. kokaiensis were induced the chilling treatment before germination for 14 days or after germination for 14 or 28 days, respectively. We performed two biological replications per flower. Data analysis was conducted according to Hammond et al. (2005) that described the methods of calibration by gDNA hybridization.
Project description:Seasonal cycles of light, temperature and precipitation provide signals that set the timing of gene expression and growth for trees. Conifers possess evergreen needles to sense and respond to year-round external signals. We monitored gene activity in Douglas-fir needles for one year and found that gene expression is dependent on light at daily and annual scales. The majority of rhythmic genes achieve maximum activity +/- 2 hours from sunrise and sunset, and +/- 20 days from the winter and summer solstices. Remarkably, the dormant period is characterized by significant gene activation, with thousands of genes achieving peak activity. This study identifies annual gene rhythms in conifers needles, and provides a framework for identifying genes that respond to other environmental cues. Background: Perennial growth in plants is the product of interdependent cycles of daily and annual stimuli that induce cycles of growth and dormancy. In conifers, needles are the key perennial organ that integrates daily and seasonal signals from light, temperature, and water availability. To understand the relationship between seasonal rhythms and seasonal gene expression responses in conifers, we examined diurnal and circannual needle mRNA accumulation in Douglas-fir (Pseudotsuga menziesii) needles at diurnal and circannual scales. Using mRNA sequencing, we sampled 6.1x10^9 microreads from 19 trees and constructed a de novo pan-transcriptome reference that includes 173,882 tree-derived transcripts. Using this reference, we mapped RNA-Seq reads from 179 samples that capture daily, seasonal, and annual variation. Results: We identified 12,042 diurnally-cyclic transcripts, 9,299 of which showed homology to annotated genes from other plant genomes, including angiosperm core clock genes. Annual analysis revealed 21,225 annually-cyclic transcripts, 17,335 of which showed homology to annotated genes from other plant genomes. The timing of maximum gene expression is associated with light quality at diurnal and photoperiod at annual scales, with two-thirds of transcripts reaching maximum expression +/- 2 hours from sunrise and sunset, and half reaching maximum expression +/- 20 days from winter and summer solstices. Comparison to published microarray-based gene expression studies in spruce (Picea) show that the rank order of expression for 760 putatively orthologous genes was significantly preserved, highlighting the generality of our findings. Conclusions: This finding highlights the extensive annual and seasonal transcriptome variability demonstrated in conifer needles. At these temporal scales, 29% of expressed transcripts showed a significant diurnal rhythm, and 58.7% showed a significant circannual rhythm. Remarkably, thousands of genes reach their annual peak activity during winter dormancy, a time of metabolic stasis. Photoperiod appears to be a dominant driver of annual transcription patterns in Douglas-fir, and these results may be general for predicting rhythmic transcription patterns in emerging gymnosperm models.
Project description:Seasonal cycles of light, temperature and precipitation provide signals that set the timing of gene expression and growth for trees. Conifers possess evergreen needles to sense and respond to year-round external signals. We monitored gene activity in Douglas-fir needles for one year and found that gene expression is dependent on light at daily and annual scales. The majority of rhythmic genes achieve maximum activity +/- 2 hours from sunrise and sunset, and +/- 20 days from the winter and summer solstices. Remarkably, the dormant period is characterized by significant gene activation, with thousands of genes achieving peak activity. This study identifies annual gene rhythms in conifers needles, and provides a framework for identifying genes that respond to other environmental cues. Background: Perennial growth in plants is the product of interdependent cycles of daily and annual stimuli that induce cycles of growth and dormancy. In conifers, needles are the key perennial organ that integrates daily and seasonal signals from light, temperature, and water availability. To understand the relationship between seasonal rhythms and seasonal gene expression responses in conifers, we examined diurnal and circannual needle mRNA accumulation in Douglas-fir (Pseudotsuga menziesii) needles at diurnal and circannual scales. Using mRNA sequencing, we sampled 6.1x10^9 microreads from 19 trees and constructed a de novo pan-transcriptome reference that includes 173,882 tree-derived transcripts. Using this reference, we mapped RNA-Seq reads from 179 samples that capture daily, seasonal, and annual variation. Results: We identified 12,042 diurnally-cyclic transcripts, 9,299 of which showed homology to annotated genes from other plant genomes, including angiosperm core clock genes. Annual analysis revealed 21,225 annually-cyclic transcripts, 17,335 of which showed homology to annotated genes from other plant genomes. The timing of maximum gene expression is associated with light quality at diurnal and photoperiod at annual scales, with two-thirds of transcripts reaching maximum expression +/- 2 hours from sunrise and sunset, and half reaching maximum expression +/- 20 days from winter and summer solstices. Comparison to published microarray-based gene expression studies in spruce (Picea) show that the rank order of expression for 760 putatively orthologous genes was significantly preserved, highlighting the generality of our findings. Conclusions: This finding highlights the extensive annual and seasonal transcriptome variability demonstrated in conifer needles. At these temporal scales, 29% of expressed transcripts showed a significant diurnal rhythm, and 58.7% showed a significant circannual rhythm. Remarkably, thousands of genes reach their annual peak activity during winter dormancy, a time of metabolic stasis. Photoperiod appears to be a dominant driver of annual transcription patterns in Douglas-fir, and these results may be general for predicting rhythmic transcription patterns in emerging gymnosperm models.