Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Transcriptional profiling of Persea americana flowers

ABSTRACT: The debate on the origin and evolution of flowers has recently entered the field of developmental genetics, with focus on the design of the ancestral floral regulatory program. Flowers can differ dramatically among angiosperm lineages, but in general, sterile perianth organs surrounding stamens (male reproductive organs) and carpels (female reproductive organs) constitute the basic floral structure. However, the basal angiosperm lineages exhibit spectacular diversity in the number, arrangement, and structure, of floral organs, while the evolutionarily derived monocot and eudicot lineages share a far more uniform floral ground plan. As such, regulatory mechanisms underlying the archetypal floral plan, for instance that of the eudicot genetic model Arabidopsis thaliana, are unlikely to apply to the original flowers. Here we show that broadly overlapping transcriptional programs characterise the floral transcriptome of the basal angiosperm Persea americana (avocado), while floral gene expression domains are typically organ-specific in Arabidopsis. Our findings extend the âfading bordersâ model for basal angiosperms from organ identity genes to the downstream floral transcriptome, and suggest that the combinatorial mechanism for organ identity may not operate in basal angiosperms as it does in Arabidopsis. Furthermore, fading expression of components of the stamen transcriptome in central and peripheral regions of Persea flowers resembles the developmental program of the hypothesized gymnosperm âfloral progenitorâ. Accordingly, in contrast to the canalized organ-specific regulatory apparatus of Arabidopsis, floral development may have been originally regulated by overlapping transcriptional cascades with fading gradients of influence from focal to bordering organs. Expression profiles of inflorescence buds, pre-meiotic floral buds, inner and outer tepals, stamens, carpels, initiating fruit, and leaves were assessed in an interwoven double loop design for eight samples with 16 arrays. Sample materials were collected from two individuals (biological replicates) cultivated on the University of Floridaâs Gainesville campus, and RNA was isolated twice for technical replication. Thus, four RNA extractions from each of the eight tissue types listed above were individually labeled with Cy3 (twice) or Cy5 (twice) and hybridized with four other Cy3 or Cy5 labeled samples as a dual channel array system.

ORGANISM(S): Persea americana

SUBMITTER: Andre Chanderbali

PROVIDER: E-GEOD-13737 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Transcriptional signatures of ancient floral developmental genetics in avocado (Persea americana; Lauraceae).

Chanderbali André S AS Albert Victor A VA Leebens-Mack Jim J Altman Naomi S NS Soltis Douglas E DE Soltis Pamela S PS

Proceedings of the National Academy of Sciences of the United States of America 20090518 22

The debate on the origin and evolution of flowers has recently entered the field of developmental genetics, with focus on the design of the ancestral floral regulatory program. Flowers can differ dramatically among angiosperm lineages, but in general, male and female reproductive organs surrounded by a sterile perianth of sepals and petals constitute the basic floral structure. However, the basal angiosperm lineages exhibit spectacular diversity in the number, arrangement, and structure of flora ...[more]

PMID: 19451627

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Project description:The fumarate and nitrate reductase regulator protein, FNR, is a global transcription factor that regulates major biochemical changes as Escherichia coli adapts from aerobic to anaerobic growth. The ability of an fnr mutant to grow anaerobically in the presence of trimethylamine-N-oxide (TMAO) as the terminal electron acceptor was exploited in microarray experiments designed to determine a minimum number of Escherichia coli K-12 MG1655 operons that are regulated directly by FNR. In an anaerobic glycerol-TMAO-fumarate medium, the fnr mutant grew as well as the parental strain, enabling us to reveal the response of the E. coli transcriptome to oxygen, nitrate and nitrite in the absence of glucose repression or artefacts due to variations in growth rate. Many of the discrepancies between previous microarray studies of the E. coli FNR regulon were resolved in this study. First data for 43 previously characterised FNR-dependent operons were analysed. The current microarray data confirmed 32 of these 43 assignments, but alone did not confirm FNR-activation of 5 operons (adhE, glpTQ, cydDC, hlyE and arcA), or FNR repression of 6 operons (hemA, narXL, tpx, yeiL, norVW or ubiCA). Thirty-six operons not previously known to be included in the FNR regulon were activated by FNR and a further 26 operons appeared to be repressed. For each of these operons, an excellent match to the consensus FNR-binding site sequence was identified. The FNR regulon therefore minimally includes at least 94, and possibly as many as 105, operons. Many FNR-activated promoters are also regulated by one or both of two nitrate- and nitrite-responsive two-component regulatory systems, NarX-NarL and NarQ-NarP. Comparison of transcripts in the parental strain and a narXL deletion mutant revealed that transcription of 51 operons is activated, directly or indirectly, by NarL in response to nitrate, and a further 41 are repressed. As phosphorylated NarL can bind to the NarP DNA target sequence, the narP gene was also deleted from the narXL mutant to reveal the extent of regulation by phosphorylated NarP. Fourteen promoters were more active in the narP+ strain than in the mutant, and a further 37 were strongly repressed. This is the first report that NarP might function as a global repressor as well as a transcription activator. The data also revealed possible new biochemical defence mechanisms against reactive nitrogen species. Keywords: genetic modification, growth conditions An fnr mutant is either unable to grow anaerobically in the presence of most terminal electron acceptors and a non-fermentable carbon source such as glycerol or lactate, or grows far more slowly than the parental strain. Under such conditions, any differences in the transcriptomes of an fnr mutant and its parental strain would be due to both direct effects of FNR, and to differences in growth rate. As glucose represses expression from some FNR-activated promoters replacement of glucose by a less repressing fermentable carbohydrate would decrease effects due to glucose repression, but to an unknown extent. We therefore exploited the fact that fnr mutants can be grown anaerobically in the presence of the non-fermentable and non-repressing carbon source, glycerol, in the presence of trimethylamine-N-oxide (TMAO) in addition to fumarate as the terminal electron acceptor. Furthermore, the presence of TMAO has a minimal effect on NarX-NarL or NarQ-NarP-dependent induction or repression. Under these conditions, the fnr mutant grows as well as the parental strain and the use of the glycerol-TMAO-fumarate medium enables us to reveal the response of the E. coli transcriptome to nitrate, nitrite and the two-component regulator system, NarX-NarL. In each large set of experiments a common pool of reference RNA isolated from bacteria that had been grown anaerobically, and in which FNR-activated genes were expressed at a significant level. A potential disadvantage of this approach was the risk that some promoters repressed by FNR would be expressed at such a low level that the microarray signals would be too low to yield reliable data. To check for this artefact, further experiments were completed in which the reference RNA was a pool of samples isolated from bacteria in the early exponential phase of aerobic growth. “Reference” RNA was isolated from at least four independent cultures grown to OD 0.5 to 0.6. “Test” RNA was isolated from three independent cultures grown to OD 0.5 to 0.6.

Dataset Information

Transcriptional profiling of Persea americana flowers

Publications

Transcriptional signatures of ancient floral developmental genetics in avocado (Persea americana; Lauraceae).

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