651
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Yuan YX, Wu J, Sun RF, Zhang XW, Xu DH, Bonnema G, Wang XW. A naturally occurring splicing site mutation in the Brassica rapa FLC1 gene is associated with variation in flowering time. J Exp Bot 2009; 60:1299-308. [PMID: 19190098 PMCID: PMC2657548 DOI: 10.1093/jxb/erp010] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Revised: 12/22/2008] [Accepted: 01/07/2009] [Indexed: 05/18/2023]
Abstract
FLOWERING LOCUS C (FLC), encoding a MADS-domain transcription factor in Arabidopsis, is a repressor of flowering involved in the vernalization pathway. This provides a good reference for Brassica species. Genomes of Brassica species contain several FLC homologues and several of these colocalize with flowering-time QTL. Here the analysis of sequence variation of BrFLC1 in Brassica rapa and its association with the flowering-time phenotype is reported. The analysis revealed that a G-->A polymorphism at the 5' splice site in intron 6 of BrFLC1 is associated with flowering phenotype. Three BrFLC1 alleles with alternative splicing patterns, including two with different parts of intron 6 retained and one with the entire exon 6 excluded from the transcript, were identified in addition to alleles with normal splicing. It was inferred that aberrant splicing of the pre-mRNA leads to loss-of-function of BrFLC1. A CAPS marker was developed for this locus to distinguish Pi6+1(G) and Pi6+1(A). The polymorphism detected with this marker was significantly associated with flowering time in a collection of 121 B. rapa accessions and in a segregating Chinese cabbage doubled-haploid population. These findings suggest that a naturally occurring splicing mutation in the BrFLC1 gene contributes greatly to flowering-time variation in B. rapa.
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Affiliation(s)
- Yu-Xiang Yuan
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
- Institute of Horticulture, Henan Academy of Agricultural Sciences, Zhengzhou 450002, China
| | - Jian Wu
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Ri-Fei Sun
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Xiao-Wei Zhang
- Institute of Horticulture, Henan Academy of Agricultural Sciences, Zhengzhou 450002, China
| | - Dong-Hui Xu
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Guusje Bonnema
- Laboratory of Plant Breeding, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Xiao-Wu Wang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
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652
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Elitzur T, Nahum H, Borovsky Y, Pekker I, Eshed Y, Paran I. Co-ordinated regulation of flowering time, plant architecture and growth by FASCICULATE: the pepper orthologue of SELF PRUNING. J Exp Bot 2009; 60:869-80. [PMID: 19174461 PMCID: PMC2652051 DOI: 10.1093/jxb/ern334] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2008] [Revised: 11/24/2008] [Accepted: 11/27/2008] [Indexed: 05/18/2023]
Abstract
Wild peppers (Capsicum spp.) are either annual or perennial in their native habitat and their shoot architecture is dictated by their sympodial growth habit. To study shoot architecture in pepper, sympodial development is described in wild type and in the classical recessive fasciculate (fa) mutation. The basic sympodial unit in wild-type pepper comprises two leaves and a single terminal flower. fasciculate plants are characterized by the formation of floral clusters separated by short internodes and miniature leaves and by early flowering. Developmental analysis of these clusters revealed shorter sympodial units and, often, precocious termination prior to sympodial leaf formation. fa was mapped to pepper chromosome 6, in a region corresponding to the tomato SELF-PRUNING (SP) locus, the homologue of TFL1 of Arabidopsis. Sequence comparison between wild-type and fa plants revealed a duplication of the second exon in the mutants' orthologue of SP, leading to the formation of a premature stop codon. Ectopic expression of FASCICULATE complemented the Arabidopsis tfl1 mutant plants and as expected, stimulated late flowering. In agreement with the major effect of FASCICULATE imposed on sympodial development, the gene transcripts were localized to the centre of sympodial shoots but could not be detected in the primary shoot. The wide range of pleiotropic effects on plant architecture mediated by a single 'flowering' gene, suggests that it is used to co-ordinate many developmental events, and thus may underlie some of the widespread variation in the Solanaceae shoot architecture.
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Affiliation(s)
- Tomer Elitzur
- Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, PO Box 6, Bet Dagan 50250, Israel
| | - Hadas Nahum
- Department of Plant Science, Weizmann Institute of Science, Rehovot, Israel
| | - Yelena Borovsky
- Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, PO Box 6, Bet Dagan 50250, Israel
| | - Irena Pekker
- Department of Plant Science, Weizmann Institute of Science, Rehovot, Israel
| | - Yuval Eshed
- Department of Plant Science, Weizmann Institute of Science, Rehovot, Israel
| | - Ilan Paran
- Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, PO Box 6, Bet Dagan 50250, Israel
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653
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Burgos-Rivera B, Ruzicka DR, Deal RB, McKinney EC, King-Reid L, Meagher RB. ACTIN DEPOLYMERIZING FACTOR9 controls development and gene expression in Arabidopsis. Plant Mol Biol 2008; 68:619-32. [PMID: 18830798 PMCID: PMC2811079 DOI: 10.1007/s11103-008-9398-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Accepted: 08/31/2008] [Indexed: 05/20/2023]
Abstract
Actin depolymerizing factors (ADF/cofilin) modulate the rate of actin filament turnover, networking cellular signals into cytoskeletal-dependent developmental pathways. Plant and animal genomes encode families of diverse ancient ADF isovariants. One weakly but ubiquitously expressed member of the Arabidopsis ADF gene family, ADF9, is moderately expressed in the shoot apical meristem (SAM). Mutant alleles adf9-1 and adf9-2 showed a 95% and 50% reduction in transcript levels, respectively. Compared to wild-type, mutant seedlings and plants were significantly smaller and adult mutant plants had decreased numbers of lateral branches and a reduced ability to form callus. The mutants flowered very early during long-day light cycles, but not during short days. adf9-1showed a several-fold lower expression of FLOWERING LOCUS C (FLC), a master repressor of the transition to flowering, and increased expression of CONSTANS, an activator of flowering. Transgenic ADF9 expression complemented both developmental and gene expression phenotypes. FLC chromatin from adf9-1 plants contained reduced levels of histone H3 lysine 4 trimethylation and lysine 9 and 14 acetylation, as well as increased nucleosome occupancy consistent with a less active chromatin state. We propose that ADF9 networks both cytoplasmic and nuclear processes within the SAM to control multicellular development.
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Affiliation(s)
| | | | - Roger B. Deal
- Fred Hutchinson Cancer Research Center, 1100 Fairview Ave North, Seattle, WA 98109, USA
| | | | - Lori King-Reid
- Department of Genetics, University of Georgia, Athens, GA 30602, USA
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654
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Yun J, Kim SG, Hong S, Park CM. Small interfering peptides as a novel way of transcriptional control. Plant Signal Behav 2008; 3:615-7. [PMID: 19513250 PMCID: PMC2634540 DOI: 10.4161/psb.3.9.6225] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Accepted: 05/02/2008] [Indexed: 05/04/2023]
Abstract
Transcription factors are key components of transcriptional regulatory networks governing virtually all aspects of plant growth and developmental processes. Their activities are regulated at various steps, including gene transcription, posttranscriptional mRNA metabolism, posttranslational modifications, nucleocytoplasmic transport, and controlled proteolytic cleavage of membrane-anchored, dormant forms. Dynamic protein dimerization also plays a critical role in this process. An exquisite regulatory scheme has recently been proposed to modulate the action of transcription factors. Small peptides possessing a protein dimerization motif but lacking the DNA-binding motif form nonfunctional heterodimers with a group of specific TFs, inhibiting their transcriptional activation activities. Extensive searches for small proteins that have a similar structural organization in the databases revealed that small peptide-mediated transcription control is not an exceptional case but would be a regulatory mechanism occurring widespread in the Arabidopsis genome.
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Affiliation(s)
- Ju Yun
- Molecular Signaling Laboratory; Department of Chemistry; Seoul National University; Seoul, Korea
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655
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Jacob Y, Michaels SD. Peering through the pore: The role of AtTPR in nuclear transport and development. Plant Signal Behav 2008; 3:62-64. [PMID: 19704774 PMCID: PMC2633964 DOI: 10.4161/psb.3.1.4903] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Accepted: 08/20/2007] [Indexed: 05/28/2023]
Abstract
In eukaryotes, most genetic material resides in a separate membrane-bound compartment known as the nucleus. Transport of cargo, such as RNA and protein, across this barrier is facilitated by the nuclear pore complex (NPC). In the July issue of Plant Physiology, we showed that a component of the NPC, Arabidopsis thaliana TPR (AtTPR), is required for normal development. Two striking phenotypes of attpr mutants are that they are early flowering and show an accumulation of polyadenylated RNA in the nucleus. In addition, the expression of several microRNAs (miRNAs) is reduced in attpr mutants. In this addendum, we have examined the effect of AtTPR on the expression of miRNA targets. Our results show that miRNA targets are more likely to be upregulated than other transcripts in attpr mutants. For example, when comparing the nuclear RNA pool between wild-type and attpr plants, we found that 75% of the miRNA targets showing a significant change in transcript level are upregulated in attpr mutants. Although the targets of some miRNAs were upregulated, other miRNA targets were relatively unaffected by attpr mutations. Thus it appears that AtTPR may be required for the proper expression or localization of a subset of miRNAs.
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Affiliation(s)
- Yannick Jacob
- Department of Biology; Indiana University; Bloomington, Indiana USA
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656
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Chia TYP, Müller A, Jung C, Mutasa-Göttgens ES. Sugar beet contains a large CONSTANS-LIKE gene family including a CO homologue that is independent of the early-bolting (B) gene locus. J Exp Bot 2008; 59:2735-48. [PMID: 18495636 PMCID: PMC2486466 DOI: 10.1093/jxb/ern129] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Revised: 04/08/2008] [Accepted: 04/10/2008] [Indexed: 05/20/2023]
Abstract
Floral transition in the obligate long-day (LD) plant sugar beet (Beta vulgaris ssp. vulgaris) is tightly linked to the B gene, a dominant early-bolting quantitative trait locus, the expression of which is positively regulated by LD photoperiod. Thus, photoperiod regulators like CONSTANS (CO) and CONSTANS-LIKE (COL) genes identified in many LD and short-day (SD)-responsive plants have long been considered constituents and/or candidates for the B gene. Until now, the photoperiod response pathway of sugar beet (a Caryophyllid), diverged from the Rosids and Asterids has not been identified. Here, evidence supporting the existence of a COL gene family is provided and the presence of Group I, II, and III COL genes in sugar beet, as characterized by different zinc-finger (B-box) and CCT (CO, CO-like, TOC) domains is demonstrated. BvCOL1 is identified as a close-homologue of Group 1a (AtCO, AtCOL1, AtCOL2) COL genes, hence a good candidate for flowering time control and it is shown that it maps to chromosome II but distant from the B gene locus. The late-flowering phenotype of A. thaliana co-2 mutants was rescued by over-expression of BvCOL1 thereby suggesting functional equivalence with AtCO, and it is shown that BvCOL1 interacts appropriately with the endogenous downstream genes, AtFT and AtSOC1 in the transgenic plants. Curiously, BvCOL1 has a dawn-phased diurnal pattern of transcription, mimicking that of AtCOL1 and AtCOL2 while contrasting with AtCO. Taken together, these data suggest that BvCOL1 plays an important role in the photoperiod response of sugar beet.
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Affiliation(s)
- T. Y. P. Chia
- Broom's Barn Research Centre, Higham, Bury St Edmunds, Suffolk IP28 6NP, UK
| | - A. Müller
- Plant Breeding Institute, Olshausenstr. 40, D-24098 Kiel, Germany
| | - C. Jung
- Plant Breeding Institute, Olshausenstr. 40, D-24098 Kiel, Germany
| | - E. S. Mutasa-Göttgens
- Broom's Barn Research Centre, Higham, Bury St Edmunds, Suffolk IP28 6NP, UK
- To whom correspondence should be addressed. E-mail:
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657
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Kim SG, Park CM. Membrane-mediated salt stress signaling in flowering time control. Plant Signal Behav 2007; 2:517-8. [PMID: 19704545 PMCID: PMC2634355 DOI: 10.4161/psb.2.6.4645] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Accepted: 06/27/2007] [Indexed: 05/04/2023]
Abstract
More than 10% of the plant-specific NAC (NAM, ATAF1/2, CUC2) transcription factors have been predicted to have alpha-helical transmembrane (TM) domain in their C-terminal regions, among which at least three members have been proven to be membrane-associated and play a role in cell cycle control and stress responses. These observations suggest that membrane-mediated regulation would be an important molecular mechanism mediating rapid transcriptional responses to internal and external stimuli in plants. Recently, we showed that a salt-responsive NTL (NTM1-Like's) transcription factor NTL8 is localized primarily in plasma membranes as dormant form and subsequently processed into transcriptionally active, nuclear form. Overexpression of an active NTL8 form exhibited delayed flowering as well as reduced growth with small curled leaves. Consistent with this, expression of FLOWERING LOCUS T (FT) and its downstream genes was significantly reduced in the transgenic plants. Furthermore, FT was notably repressed by high salt. These results indicate that NTL8 mediates salt-responsive flowering via FT in Arabidopsis and that membrane-mediated transcription regulation underlies the salt signaling in mediating flowering initiation.
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Affiliation(s)
- Sang-Gyu Kim
- Molecular Signaling Laboratory; Department of Chemistry; Seoul National University; Seoul, Korea
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658
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Abstract
NUA (Nuclear Pore Anchor), the Arabidopsis homolog of Tpr (Translocated Promoter Region), is one of the few nuclear pore proteins conserved between animals, yeast and plants. In the May issue of Plant Cell, we report that null mutants of NUA show a pleiotropic, early flowering phenotype accompanied by changes in SUMo and RNA homeostasis. We have shown that the early flowering phenotype is caused by changed abundances of flowering time regulators involved in several pathways. Arabidopsis nua mutants phenocopy mutants lacking the ESD4 (EARlY IN ShoRT DAYS 4) SUMo protease, similar to mutants of their respective yeast homologs. however, in contrast to the comparable yeast mutants, ESD4 does not appear to be delocalized from the nuclear pore in nua mutants. Taken together, our experimental data suggests a role for NUA in controlling mRNA export from the nucleus as well as SUMo protease activity at the nuclear pore, comparable but not identical to its homologs in other eukaryotes. Furthermore, characterization of NUA illustrates a potential link at the nuclear pore between SUMo modification, RNA homeostasis and plant developmental control.
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Affiliation(s)
- Xianfeng Morgan Xu
- Department of Plant Cellular and Molecular Biology and Plant Biotechnology Center; Ohio State University; Columbus, Ohio USA
| | - Annkatrin Rose
- Department of Biology; Appalachian State University; Boone, North Carolina USA
| | - Iris Meier
- Department of Plant Cellular and Molecular Biology and Plant Biotechnology Center; Ohio State University; Columbus, Ohio USA
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659
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Scarcelli N, Cheverud JM, Schaal BA, Kover PX. Antagonistic pleiotropic effects reduce the potential adaptive value of the FRIGIDA locus. Proc Natl Acad Sci U S A 2007; 104:16986-91. [PMID: 17940010 PMCID: PMC2040464 DOI: 10.1073/pnas.0708209104] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2007] [Indexed: 01/27/2023] Open
Abstract
Although the occurrence of epistasis and pleiotropy is widely accepted at the molecular level, its effect on the adaptive value of fitness-related genes is rarely investigated in plants. Knowledge of these features of a gene is critical to understand the molecular basis of adaptive evolution. Here we investigate the importance of pleiotropy and epistasis in determining the adaptive value of a candidate gene using the gene FRI (FRIGIDA), which is thought to be the major gene controlling flowering time variation in Arabidopsis thaliana. The effect of FRI on flowering time was analyzed in an outbred population created by randomly mating 19 natural accessions of A. thaliana. This unique population allows the estimation of FRI effects independent of any linkage association with other loci due to demographic processes or to coadapted genes. It also allows for the estimation of pleiotropic effects of FRI on fitness and inflorescence architecture. We found that FRI explains less variation in flowering time than previously observed among natural accessions, and interacts epistatically with the FLC locus. Although early flowering plants produce more fruits under spring conditions, and nonfunctional alleles of FRI were associated with early flowering, variation at FRI was not associated with fitness. We show that nonfunctional FRI alleles have negative pleiotropic effects on fitness by reducing the numbers of nodes and branches on the inflorescence. We propose that these antagonistic pleiotropic effects reduce the adaptive value of FRI, and helps explain the maintenance of alternative life history strategies across natural populations of A. thaliana.
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Affiliation(s)
- Nora Scarcelli
- *Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - James M. Cheverud
- Department of Anatomy and Neurobiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110; and
| | - Barbara A. Schaal
- Department of Biology, Washington University, One Brookings Drive, St. Louis, MO 63110
| | - Paula X. Kover
- *Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
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660
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Abstract
The recent release of the Populus trichocarpa genome sequence will dramatically enhance the efficiency of functional and comparative genomics research in trees. This provides researchers studying various developmental processes related to the perennial and tree life strategies with a completely new set of tools. Intimately associated with the life strategy of trees are their abilities to maintain juvenile or nonflowering phases for years to decades, and once reproductively competent, to alternate between the production of vegetative and reproductive shoots. Most of what we know about the regulation of the floral transition comes from research on Arabidopsis thaliana, a small, herbaceous, rapid-cycling, annual plant. In this review, we discuss the similarities and differences between Arabidopsis and tree flowering, and how recent findings in Arabidopsis, coupled to comparative and functional genomics in poplars, will help answer the question of how tree maturation and floral initiation is regulated.
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Affiliation(s)
- Amy M Brunner
- Department of Forest Science, Oregon State University, Corvallis, OR 97331-5752, USA
| | - Ove Nilsson
- Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden
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661
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Parra-Tabla V, Vargas CF. Phenology and phenotypic natural selection on the flowering time of a deceit-pollinated tropical orchid, Myrmecophila christinae. Ann Bot 2004; 94:243-50. [PMID: 15205176 PMCID: PMC4242159 DOI: 10.1093/aob/mch134] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2003] [Revised: 02/23/2004] [Accepted: 04/06/2004] [Indexed: 05/22/2023]
Abstract
BACKGROUND AND AIMS Flowering phenology is described and the effect of flowering time on pollination success is evaluated in the deceit-pollinated tropical orchid, Myrmecophila christinae. It was expected that, due to this species' deceit pollination strategy and low observed pollinator visit rate, there would be a higher probability of natural selection events favouring individuals flowering away from the population flowering peak. METHODS The study covers two consecutive years and four populations of M. christinae located along the north coast of the Yucatán Peninsula. For phenological and pollination success data, a total of 110 individuals were monitored weekly in 1998, and 83 individuals in 1999, during all the flowering and fruiting season. KEY RESULTS The results showed significant differences in the probability of donating and receiving pollen throughout the flowering season. The probability of receiving or donating pollen increased the further an individual flowering was from the flowering peak. Regression analysis showed directional and disruptive phenotypic natural selection gradients, suggesting the presence of selection events unfavourable to flowering during flowering peak, for both male success (pollen removal) and female success (fruit production). However, the intensity and significance of the natural selection events varied between populations from year to year. The variation between seasons and populations was apparently due to variations in the density of reproductive individuals in each population and each season. CONCLUSIONS As in other deceit-pollinated orchids, natural selection in M. christinae favours individuals flowering early or late in relation to population peak flowering. However, results also suggested a fluctuating regime of selective events act on flowering time of M. christinae.
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Affiliation(s)
- Victor Parra-Tabla
- Departamento de Ecología, Campus de Ciencias Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, AP 4-116, Col. Itzimná, 97100, Mérida, Yucatán, México.
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662
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Thingnaes E, Torre S, Ernstsen A, Moe R. Day and night temperature responses in Arabidopsis: effects on gibberellin and auxin content, cell size, morphology and flowering time. Ann Bot 2003; 92:601-12. [PMID: 12922976 PMCID: PMC4243678 DOI: 10.1093/aob/mcg176] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The effect of 16 different day (DT) and night (NT) temperature combinations (DT and NT 12, 17, 22 and 27 degrees C) on rosette leaf growth, flower stem elongation and flowering time in Arabidopsis thaliana Ler was investigated. Final leaf length decreased with increasing NT due to a combination of reduced elongation period and reduced elongation rate. Final stem length increased with increasing DT due to increased elongation rate, and decreased with increasing NT due to a decrease in elongation period. Under NT 27 degrees C, however, stem elongation rate increased greatly, resulting in the same final stem length as under NT 12 degrees C. The transition to flowering was accelerated by increasing NT. A linear regression analysis was performed to clarify the relationship between final leaf length, final stem length and flowering time with DIF (DT minus NT) and/or ADT (average daily temperature). For all three variables, the effect of DIF depended on ADT and vice versa. The relationship of final stem length with DIF also depended on the temperature range. Increased cell volume in flower stems developing at DT/NT 22/12 degrees C gave rise to longer and thicker stems compared with stems developing at DT/NT 12/22 degrees C. GC-MS analysis (gas chromatography-mass spectrometry) showed that the endogenous level of IAA was 56 % higher in stems grown under DT/NT 22/12 degrees C compared with DT/NT 12/22 degrees C. Of the 12 gibberellins analysed, however, only the level of non-bioactive GA29 was affected by the temperature treatment.
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Affiliation(s)
- Elin Thingnaes
- Department of Horticulture and Crop Sciences, Agricultural University of Norway, N-1432 As, Norway.
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663
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Izawa T, Oikawa T, Sugiyama N, Tanisaka T, Yano M, Shimamoto K. Phytochrome mediates the external light signal to repress FT orthologs in photoperiodic flowering of rice. Genes Dev 2002; 16:2006-20. [PMID: 12154129 PMCID: PMC186415 DOI: 10.1101/gad.999202] [Citation(s) in RCA: 284] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2002] [Accepted: 06/11/2002] [Indexed: 11/25/2022]
Abstract
Phytochromes confer the photoperiodic control of flowering in rice (Oryza sativa), a short-day plant. To better understand the molecular mechanisms of day-length recognition, we examined the interaction between phytochrome signals and circadian clocks in photoperiodic-flowering mutants of rice. Monitoring behaviors of circadian clocks revealed that phase setting of circadian clocks is not affected either under short-day (SD) or under long-day (LD) conditions in a phytochrome-deficient mutant that shows an early-flowering phenotype with no photoperiodic response. Non-24-hr-light/dark-cycle experiments revealed that a rice counterpart gene of Arabidopsis CONSTANS (CO), named PHOTOPERIOD SENSITIVITY 1 (Heading date 1) [SE1 (Hd1)], functions as an output of circadian clocks. In addition, the phytochrome deficiency does not affect the diurnal mRNA expression of SE1 upon floral transition. Downstream floral switch genes were further identified with rice orthologs of Arabidopsis FLOWERING LOCUS T (FT). Our RT-PCR data indicate that phytochrome signals repress mRNA expression of FT orthologs, whereas SE1 can function to promote and suppress mRNA expression of the FT orthologs under SD and LD, respectively. This SE1 transcriptional activity may be posttranscriptionally regulated and may depend on the coincidence with Pfr phytochromes. We propose a model to explain how a short-day plant recognizes the day length in photoperiodic flowering.
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Affiliation(s)
- Takeshi Izawa
- Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, Ikoma, Nara 630-0101, Japan.
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