Characterization of tomato (Solanum lycopersicum L.) mutants affected in their flowering time and in the morphogenesis of their reproductive structure
Muriel QuinetCéline DuboisMarie-Christine GoffinJaime L. ChaoVincent DielenHenri BatokoMarc BoutryJean‐Marie Kinet
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The impact of the season on flowering time and the organization and morphogenesis of the reproductive structures are described in three tomato mutants: compound inflorescence (s), single flower truss (sft), and jointless (j), respectively, compared with their wild-type cultivars Ailsa Craig (AC), Platense (Pl), and Heinz (Hz). In all environmental conditions, the sft mutant flowered significantly later than its corresponding Pl cultivar while flowering time in j was only marginally, but consistently, delayed compared with Hz. The SFT gene and, to a lesser extent, the J gene thus appear to be constitutive flowering promoters. Flowering in s was delayed in winter but not in summer compared with the AC cultivar, suggesting the existence of an environmentally regulated pathway for the control of floral transition. The reproductive structure of tomato is a raceme-like inflorescence and genes regulating its morphogenesis may thus be divided into inflorescence and floral meristem identity genes as in Arabidopsis. The s mutant developed highly branched inflorescences bearing up to 200 flowers due to the conversion of floral meristems into inflorescence meristems. The S gene appears to be a floral meristem identity gene. Both sft and j mutants formed reproductive structures containing flowers and leaves and reverting to a vegetative sympodial growth. The SFT gene appears to regulate the identity of the inflorescence meristem of tomato and is also involved, along with the J gene, in the maintenance of this identity, preventing reversion to a vegetative identity. These results are discussed in relation to knowledge accumulated in Arabidopsis and to domestication processes.Keywords:
Raceme
The evolutionary pathway of monophylly characterized by a sole conspicuous leaf (macrocotyledon) and a cotyledonary inflorescence in Gesneriaceae is uncertain. This article describes the developmental anatomy of the caulescent species Streptocarpus pallidiflorus and compares it with unifoliate species. During and after seed germination, the root apical meristem arises exogenously and develops into the primary root, while the shoot apical meristem (SAM) arises in the actual center of the region between the anisocotyledons and produces the primary shoot. The macrocotyledon, like the foliage leaves, grows determinately because of the disappearance of the basal meristem during development. The developmental manner in which multiple axillary meristems form basipetally only on the side facing the subtending leaf or the macrocotyledon is similar to the basipetal initiation of secondary inflorescence on the primary inflorescence in the axil of the macrocotyledon in unifoliate congeners. We propose an evolutionary scenario for monophylly in which the embryonic SAM has been lost or suppressed in association with the establishment of the indeterminate basal meristem in the macrocotyledon and transfer of the vegetative axillary meristem at the macrocotyledon into an inflorescence meristem.
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One of the key events in plant development is the initiation of lateral organs from the flanks of the meristem. In grasses, the inflorescence meristem (IM) reiteratively initiates a series of lateral meristems with slightly different fates. Our understanding of the genes and networks that regulate
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After a vegetative phase, plants initiate the floral transition in response to both environmental and endogenous cues to optimize reproductive success. During this process, the vegetative shoot apical meristem (SAM), which was producing leaves and branches, becomes an inflorescence SAM and starts producing flowers. Inflorescences can be classified in two main categories, depending on the fate of the inflorescence meristem: determinate or indeterminate. In determinate inflorescences, the SAM differentiates directly, or after the production of a certain number of flowers, into a flower, while in indeterminate inflorescences the SAM remains indeterminate and produces continuously new flowers. Even though indeterminate inflorescences have an undifferentiated SAM, the number of flowers produced by a plant is not indefinite and is characteristic of each species, indicating that it is under genetic control. In Arabidopsis thaliana and other species with indeterminate inflorescences, the end of flower production occurs by a regulated proliferative arrest of inflorescence meristems on all reproductive branches that is reminiscent of a state of induced dormancy and does not involve the determination of the SAM. This process is controlled genetically by the FRUITFULL-APETALA2 (FUL-AP2) pathway and by a correlative control exerted by the seeds through a mechanism not well understood yet. In the absence of seeds, meristem proliferative arrest does not occur, and the SAM remains actively producing flowers until it becomes determinate, differentiating into a terminal floral structure. Here we show that the indeterminate growth habit of Arabidopsis inflorescences is a facultative condition imposed by the meristematic arrest directed by FUL and the correlative signal of seeds. The terminal differentiation of the SAM when seed production is absent correlates with the induction of AGAMOUS expression in the SAM. Moreover, terminal flower formation is strictly dependent on the activity of FUL, as it was never observed in ful mutants, regardless of the fertility of the plant or the presence/absence of the AG repression exerted by APETALA2 related factors.
Indeterminate growth
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The relationship between fruit development and the proliferative capacities of inflorescence meristems has been examined in Arabidopsis thaliana. In the wild-type Landsberg erecta (Ler) line, flower production ceases coordinately on all inflorescence branches by a process we have designated global proliferative arrest (GPA). Morphological studies indicate that GPA involves a cessation of proliferative activity at the meristems, but a retention of the structural characteristics of the proliferating meristems. GPA does not occur in the male-sterile (ms1-1) line, nor in wild-type Ler when fruits are surgically removed. In these cases, inflorescence meristems continue to proliferate, ultimately terminating by a different process, designated terminal differentiation, in which disruptions in patterning at the apex are followed by the loss of the inflorescence meristem. We present an argument that GPA is mediated by a specific communication system between inflorescence meristems and developing fruits. Analysis of reduced-fertility mutants provided evidence that GPA is dependent on seed development specifically. Mutations conferring hormone deficiency or insensitivity did not disrupt the correlative interactions leading to GPA.
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The aim of this study was to use multivariate methods and Pearson and partial correlations to disregard phenotypic characteristics that contribute little to differentiation between Brachiaria ruziziensis genotypes.Eighty-one genotypes of B. ruziziensis were assessed in completely randomized blocks with three replications.Ten phenotypic characteristics were assessed: plant height, leaf length, leaf width, sheath length, length of the flower stem, length of the inflorescence axis, number of racemes per inflorescence, length of the basal raceme, number of spikelets per basal raceme, and width of the rachis.The best traits for differentiation between genotypes were determined by assessing relative contribution to diversity, canonical variables, as well as Pearson and partial correlations.Four canonical variables were found to account for 57% of the overall variation, while plant height, sheath length, and number of racemes per inflorescence were considered traits that could potentially be disregarded in future assessments.
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Flowering plants have developed many ways to arrange their flowers. A flower-bearing branch or system of branches is called an inflorescence. The number of flowers that an inflorescence contains ranges from a single flower to endless flower-clusters. Over the past centuries, botanists have classified inflorescences based on their morphology, which has led to an unfortunate maze of complex botanical terminology. With the rise of molecular developmental biology, research has become increasingly focused on how inflorescences develop, rather than on their morphology. It is the decisions taken by groups of stem cells at the growing tips of shoots, called meristems, on when and where to produce a flower or a shoot that specify the course of inflorescence development. Modelling is a helpful aid to follow the consequences of these decisions for inflorescence development. The so-called transient model can produce the broad inflorescence types: cyme, raceme, and panicle, into which most inflorescences found in nature can be classified. The analysis of several inflorescence branching mutants has led to a solid understanding of cymose inflorescence development in petunia (Petunia hybrida). The cyme of petunia is a distinct body plan compared with the well-studied racemes of Arabidopsis and Antirrhinum, which provides an excellent opportunity to study evolutionary developmental biology (evo-devo) related questions. However, thus far, limited use has been made of this opportunity, which may, at least in part, be due to researchers getting lost in the terminology. Some general issues are discussed here, while focusing on inflorescence development in petunia.
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Petunia
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Tomato is a major crop plant and several mutants have been selected for breeding but also for isolating important genes that regulate flowering and sympodial growth. Besides, current research in developmental biology aims at revealing mechanisms that account for diversity in inflorescence architectures. We therefore found timely to review the current knowledge of the genetic control of flowering in tomato and to integrate the emerging network into modeling attempts. We developped a kinetic model of the tomato inflorescence development where each meristem was represented by its 'vegetativeness' (V), reflecting its maturation state towards flower initiation. The model followed simple rules: maturation proceeded continuously at the same rate in every meristem (dV); floral transition and floral commitment occurred at threshold levels of V; lateral meristems were initiated with a gain of V (ΔV) relative to the V level of the meristem from which they derived. This last rule created a link between successive meristems and gave to the model its zigzag shape. We next exploited the model to explore the diversity of morphotypes that could be generated by varying dV and ΔV and matched them with existing mutant phenotypes. This approach, focused on the development of the primary inflorescence, allowed us to elaborate on the genetic regulation of the kinetic model of inflorescence development. We propose that the lateral inflorescence meristem fate in tomato is closer to an immature flower meristem than to the inflorescence meristem of Arabidopsis. In the last part of our paper, we extend our thought to spatial regulators that should be integrated in a next step for unraveling the relationships between the different meristems that participate to sympodial growth.
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The paper describes the sequence and pattern of inflorescence differentiation in six determinate and three indeterminate varieties of Phaseolus vulgaris. The terminal inflorescence of determinate varieties is a compound raceme possessing a peduncle bearing triads—branch inflorescences, each consisting of three flower buds developed acropetally on a condensed axis. Irrespective of the number of leaves on the main stem the bud primordium in the axil of the uppermost leaf differentiates into the first triad on the plant. In indeterminate varieties, the first formed triad arises at the lowermost node of the first formed lateral inflorescence, the position of which on the main stem is a varietal characteristic.
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Primordium
Main stem
Peduncle (anatomy)
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Handayani T. 2017. Flower morphology, floral development and insect visitors to flowers of Nepenthes mirabilis. Biodiversitas 18: 1624-1631. Nepenthes mirabilis Druce is a commercial ornamental pitcher plant belonging to the Nepenthaceae. This species is often used as a parent plant in artificial crossbreeding. The plant is also used in traditional medicine, rope-making, handicraft, and bouquets. Flower development and pollen maturity are important factors in pitcher plant crossbreeding. However, information about its flowering is still lacking. This study aimed to record the flower morphology, flower development, and faunal visitors to male inflorescences of N. mirabilis planted in Bogor Botanic Gardens, West Java, Indonesia. Twelve racemes of flowers were taken as a sample for observing the process of inflorescence development, while ten flowers on each raceme were observed for investigating the flowering pattern of individual flowers. The morphology of flowers, the process of inflorescence development, the flowering pattern for individual flowers, the number of open flowers, the longevity of anthesis, and the appearance of insect (and/or other faunal) visitors to flowers were observed and recorded, using naked eyes, a hand lens, and a camera. Six phases of inflorescence development were identified: inflorescence bud phase, raceme phase, the opening of the raceme-protecting sheath phase, inflorescence-stalk and flowerstalk growth phase, open flower phase and pollen maturity phase. Four phases of flower development were observed: growth of flower bud, the opening of tepals, pollen maturation, and flower senescence. The pattern of anthesis within an inflorescence was acropetal. The number of flowers per raceme was 56 to 163. The peak duration of anthesis of a flower was 11 days (30.7% of flowers). The length of the raceme-stalks was 17-31 cm. The length of the racemes was 23-38 cm. The most common visitors to the flowers were stingless bees, Trigona apicalis.
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Anthesis
Tepal
Bud
Ornamental plant
Perianth
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