RESUMO
KEY MESSAGE: We characterized genes that function in the photoperiodic flowering pathway in cassava. Transcriptome analysis of field-grown plants revealed characteristic expression patterns of these genes, demonstrating that field-grown cassava experiences two distinct developmental transitions. Cassava is an important crop for both edible and industrial purposes. Cassava develops storage roots that accumulate starch, providing an important source of staple food in tropical regions. To facilitate cassava breeding, it is important to elucidate how flowering is controlled. Several important genes that control flowering time have been identified in model plants; however, comprehensive characterization of these genes in cassava is still lacking. In this study, we identified genes encoding central flowering time regulators and examined these sequences for the presence or absence of conserved motifs. We found that cassava shares conserved genes for the photoperiodic flowering pathway, including florigen, anti-florigen and its associated transcription factor (GIGANTEA, CONSTANS, FLOWERING LOCUS T, CENTRORADIALIS/TERMINAL FLOWER1 and FD) and florigen downstream genes (SUPRESSOR OF OVEREXPRESSION OF CONSTANS1 and APETALA1/FRUITFUL). We conducted RNA-seq analysis of field-grown cassava plants and characterized the expression of flowering control genes. Finally, from the transcriptome analysis we identified two distinct developmental transitions that occur in field-grown cassava.
Assuntos
Flores/crescimento & desenvolvimento , Flores/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/genética , Regulação da Expressão Gênica de Plantas/genética , Manihot/metabolismo , Motivos de Aminoácidos , Sequência de Aminoácidos , Colômbia , Florígeno/antagonistas & inibidores , Florígeno/metabolismo , Flores/genética , Perfilação da Expressão Gênica , Manihot/genética , Manihot/crescimento & desenvolvimento , Filogenia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Alinhamento de SequênciaRESUMO
A major issue in modern agriculture is water loss through stomata during photosynthetic carbon assimilation. In water-limited ecosystems, annual plants have strategies to synchronize their growth and reproduction to the availability of water. Some species or ecotypes of flowers are early to ensure that their life cycles are completed before the onset of late season terminal drought ("drought escape"). This accelerated flowering correlates with low water-use efficiency (WUE). The molecular players and physiological mechanisms involved in this coordination are not fully understood. We analyzed WUE using gravimetry, gas exchange, and carbon isotope discrimination in florigen deficient (sft mutant), wild-type (Micro-Tom), and florigen over-expressing (SFT-ox) tomato lines. Increased florigen expression led to accelerated flowering time and reduced WUE. The low WUE of SFT-ox was driven by higher stomatal conductance and thinner leaf blades. This florigen-driven effect on WUE appears be independent of abscisic acid (ABA). Our results open a new avenue to increase WUE in crops in an ABA-independent manner. Manipulation of florigen levels could allow us to produce crops with a life cycle synchronized to water availability.
Assuntos
Florígeno/metabolismo , Solanum lycopersicum/metabolismo , Água/fisiologia , Ácido Abscísico/metabolismo , Isótopos de Carbono/metabolismo , Produtos Agrícolas/genética , Produtos Agrícolas/metabolismo , Secas , Ecótipo , Flores/genética , Flores/metabolismo , Regulação da Expressão Gênica de Plantas , Solanum lycopersicum/genética , Fotossíntese , Desenvolvimento Vegetal , Folhas de Planta/genética , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Estômatos de Plantas/genética , Estômatos de Plantas/metabolismoRESUMO
BACKGROUND: Reliable indicators for the onset of flowering are not available for most perennial monocarpic species, representing a drawback for crops such as bamboo, agave and banana. The ability to predict and control the transition to the reproductive stage in A. tequilana would represent an advantage for field management of agaves for tequila production and for the development of a laboratory model for agave species. RESULTS: Consistent morphological features could not be determined for the vegetative to reproductive transition in A. tequilana. However, changes in carbohydrate metabolism where sucrose decreased and fructans of higher degree of polymerization increased in leaves before and after the vegetative to reproductive transition were observed. At the molecular level, transcriptome analysis from leaf and shoot apical meristem tissue of A. tequilana plants from different developmental stages identified OASES as the most effective assembly program and revealed evidence for incomplete transcript processing in the highly redundant assembly obtained. Gene ontology analysis uncovered enrichment for terms associated with carbohydrate and hormone metabolism and detailed analysis of expression patterns for individual genes revealed roles for specific Flowering locus T (florigen), MADS box proteins, gibberellins and fructans in the transition to flowering. CONCLUSIONS: Based on the data obtained, a preliminary model was developed to describe the regulatory mechanisms underlying the initiation of flowering in A. tequilana. Identification of specific promoter and repressor Flowering Locus T and MADS box genes facilitates functional analysis and the development of strategies to modulate the vegetative to reproductive transition in A. tequilana.