Flower Organogenesis Research Articles

Genome-Wide Characterization of MADS-box Genes Identifies Candidates Associated with Flower and Fruit Development in Loquat (Eriobotrya japonica Lindl.)

The MADS-box transcription factors have garnered substantial attention due to their crucial involvement in various biological processes, particularly in flower organogenesis. A comprehensive investigation into the MADS-box genes remains lacking in loquat (Eriobotrya japonica Lindl.). In the current study, to preliminarily explore the potential candidate genes related to flower and fruit development, a genome-wide analysis was carried out to identify and characterize the MADS-box gene family in loquat. Among the 125 identified EjMADS-box members, 49 genes belonged to type Ⅰ, which were subsequently assigned to three subfamilies: Mα (25 genes), Mβ (10 genes), and Mγ (14 genes). Additionally, 76 genes fell under type II, which were categorized into two groups: MIKCC (70 genes) and MIKC* (6 genes). Through the collinearity analysis and comparison of the gene numbers between loquat and other Rosaceae genomes, it was revealed that the type Ⅱ MADS-box members were expanded in Maloideae after a whole genome duplication. The gene expression analysis utilizing various tissues during flower development revealed that the expression patterns of the ABCDE model homologs were conserved in loquat. In addition, several candidate genes potentially involved in flower bud differentiation (EjMADS107/109) and fruit expansion (EjMADS24/46/49/55/61/67/77/86) were identified. This analysis could serve as a fundamental basis for investigating the molecular functions of the MADS-box genes in the development of flowers as well as fruits in loquat.

Hormones regulate the flowering process in saffron differently depending on the developmental stage.

Flowering in saffron is a highly complex process regulated by the synchronized action of environmental cues and endogenous signals. Hormonal regulation of flowering is a very important process controlling flowering in several plants, but it has not been studied in saffron. Flowering in saffron is a continual process completed in months with distinct developmental phases, mainly divided into flowering induction and flower organogenesis/formation. In the present study, we investigated how phytohormones affect the flowering process at different developmental stages. The results suggest that different hormones differentially affect flower induction and formation in saffron. The exogenous treatment of flowering competent corms with abscisic acid (ABA) suppressed both floral induction and flower formation, whereas some other hormones, like auxins (indole acetic acid, IAA) and gibberellic acid (GA), behaved contrarily at different developmental stages. IAA promoted flower induction, while GA suppressed it; however, GA promoted flower formation, whereas IAA suppressed it. Cytokinin (kinetin) treatment suggested its positive involvement in flower induction and flower formation. The expression analysis of floral integrator and homeotic genes suggests that ABA might suppress floral induction by suppressing the expression of the floral promoter (LFY, FT3) and promoting the expression of the floral repressor (SVP) gene. Additionally, ABA treatment also suppressed the expression of the floral homeotic genes responsible for flower formation. GA reduces the expression of flowering induction gene LFY, while IAA treatment upregulated its expression. In addition to these genes, a flowering repressor gene, TFL1-2, was also found to be downregulated in IAA treatment. Cytokinin promotes flowering induction by increasing the expression levels of the LFY gene and decreasing the TFL1-2 gene expression. Moreover, it improved flower organogenesis by increasing the expression of floral homeotic genes. Overall, the results suggest that hormones differently regulate flowering in saffron via regulating floral integrator and homeotic gene expression.

The collaborative mode by PmSVPs and PmDAMs reveals neofunctionalization in the switch of the flower bud development and dormancy for Prunus mume.

Prunus mume (Rosaceae, Prunoideae) serves as an excellent ornamental woody plant with a large-temperature-range cultivation scope. Its flower buds require a certain low temperature to achieve flowering circulation. Thus, it is important to delve into the processes of flower bud differentiation and dormancy, which affected its continuous flowering. These processes are generally considered as regulation by the MADS-box homologs, SHORT VEGETATIVE PHASE (SVP), and DORMANCY-ASSOCIATED MADS-BOX (DAM). However, a precise model on their interdependence and specific function, when acting as a complex in the flower development of P. mume, is needed. Therefore, this study highlighted the integral roles of PmDAMs and PmSVPs in flower organ development and dormancy cycle. The segregation of PmDAMs and PmSVPs in a different cluster suggested distinct functions and neofunctionalization. The expression pattern and yeast two-hybrid assays jointly revealed that eight genes were involved in the floral organ development stages, with PmDAM1 and PmDAM5 specifically related to prolificated flower formation. PmSVP1-2 mingled in the protein complex in bud dormancy stages with PmDAMs. Finally, we proposed the hypothesis that PmSVP1 and PmSVP2 could combine with PmDAM1 to have an effect on flower organogenesis and interact with PmDAM5 and PmDAM6 to regulate flower bud dormancy. These findings could help expand the current molecular mechanism based on MADS-box genes during flower bud development and dormancy.

A spatiotemporal atlas of organogenesis in the development of orchid flowers.

Development of floral organs exhibits complex molecular mechanisms involving the co-regulation of many genes specialized and precisely functioning in various tissues and developing stages. Advance in spatial transcriptome technologies allows for quantitative measurement of spatially localized gene abundance making it possible to bridge complex scenario of flower organogenesis with genome-wide molecular phenotypes. Here, we apply the 10× Visium technology in the study of the formation of floral organs through development in an orchid plant, Phalaenopsis Big Chili. Cell-types of early floral development including inflorescence meristems, primordia of floral organs and identity determined tissues, are recognized based on spatial expression distribution of thousands of genes in high resolution. In addition, meristematic cells on the basal position of floral organs are found to continuously function in multiple developmental stages after organ initiation. Particularly, the development of anther, which primordium starts from a single spot to multiple differentiated cell-types in later stages including pollinium and other vegetative tissues, is revealed by well-known MADS-box genes and many other downstream regulators. The spatial transcriptome analyses provide comprehensive information of gene activity for understanding the molecular architecture of flower organogenesis and for future genomic and genetic studies of specific cell-types.

THE ANNUAL CYCLE OF DIFFERENTIATION OF THE RUDIMENTS OF PEACH FLOWERS AFTER THE SEVERE WINTER OF 2020-2021

The article sets the timeframe for the main phenological stages of peach, as well as the required amount of effective temperatures above +5 °C for their passing and growing season length based on the example of the variety of Belarusian selection Loiko.
 The terms of the beginning of an organogenesis of flower rudiments after a severe winter and damage of generative buds, 
 skeletal branches are outlined. The peculiarities of the differentiation process during the growing season and the required amounts of effective temperatures for each stage of flower organogenesis in the central zone of Belarus are presented.
 The data obtained show that in late November the process of differentiation in most generative buds stops at stage VII b
 with a well-defined rudiment of the pistil and its clear differentiation into stigma and style. In the case of thawing during the winter, the process of organogenesis does not stop, and in February the development of flower buds in the generative buds
 reaches stage VIII with the formation of the ovary and the growth of stamens with anthers of characteristic shape.

The MADS-box gene FveSEP3 plays essential roles in flower organogenesis and fruit development in woodland strawberry

Flower and fruit development are two key steps for plant reproduction. The ABCE model for flower development has been well established in model plant species; however, the functions of ABCE genes in fruit crops are less understood. In this work, we identified an EMS mutant named R27 in woodland strawberry (Fragaria vesca), showing the conversion of petals, stamens, and carpels to sepaloid organs in a semidominant inheritance fashion. Mapping by sequencing revealed that the class E gene homolog FveSEP3 (FvH4_4g23530) possessed the causative mutation in R27 due to a G to E amino acid change in the conserved MADS domain. Additional fvesep3CR mutants generated by CRISPR/Cas9 displayed similar phenotypes to fvesep3-R27. Overexpressing wild-type or mutated FveSEP3 in Arabidopsis suggested that the mutation in R27 might cause a dominant-negative effect. Further analyses indicated that FveSEP3 physically interacted with each of the ABCE proteins in strawberry. Moreover, both R27 and fvesep3CR mutants exhibited parthenocarpic fruit growth and delayed fruit ripening. Transcriptome analysis revealed that both common and specific differentially expressed genes were identified in young fruit at 6–7 days post anthesis (DPA) of fvesep3 and pollinated wild type when compared to unpollinated wild type, especially those in the auxin pathway, a key hormone regulating fruit set in strawberry. Together, we provided compelling evidence that FveSEP3 plays predominant E functions compared to other E gene homologs in flower development and that FveSEP3 represses fruit growth in the absence of pollination and promotes fruit ripening in strawberry.

Genome-Wide Identification and Expression Analysis of MADS-Box Family Genes in Litchi (Litchi chinensis Sonn.) and Their Involvement in Floral Sex Determination.

Litchi possesses unique flower morphology and adaptive reproduction strategies. Although previous attention has been intensively devoted to the mechanisms underlying its floral induction, the molecular basis of flower sex determination remains largely unknown. MADS-box genes are promising candidates for this due to their significant roles in various aspects of inflorescence and flower organogenesis. Here, we present a detailed overview of phylogeny and expression profiles of 101 MADS-box genes that were identified in litchi. These LcMADSs are unevenly located across the 15 chromosomes and can be divided into type I and type II genes. Fifty type I MADS-box genes are subdivided into Mα, Mβ and Mγ subgroups, while fifty-one type II LcMADSs consist of 37 MIKCC -type and 14 MIKC *-type genes. Promoters of both types of LcMADS genes contain mainly ABA and MeJA response elements. Tissue-specific and development-related expression analysis reveal that LcMADS51 could be positively involved in litchi carpel formation, while six MADS-box genes, including LcMADS42/46/47/75/93/100, play a possible role in stamen development. GA is positively involved in the sex determination of litchi flowers by regulating the expression of LcMADS51 (LcSTK). However, JA down-regulates the expression of floral organ identity genes, suggesting a negative role in litchi flower development.

Creating a novel petal regeneration system for function identification of colour gene of grape hyacinth

BackgroundGrape hyacinth (Muscari spp.) is one of the most important ornamental bulbous plants. However, its lengthy juvenile period and time-consuming transformation approaches under the available protocols impedes the functional characterisation of its genes in flower tissues. In vitro flower organogenesis has long been used to hasten the breeding cycle of plants but has not been exploited for shortening the period of gene transformation and characterisation in flowers.ResultsA petal regeneration system was established for stable transformation and function identification of colour gene in grape hyacinth. By culturing on Murashige and Skoog medium (MS) with 0.45 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 8.88 μM 6-benzyladenine (6-BA), during the colour-changing period, the flower bud explants gave rise to regeneration petals in less than 3 months, instead of the 3 years required in field-grown plants. By combining this system with Agrobacterium-mediated transformation, a glucuronidase reporter gene (GUS) was delivered into grape hyacinth petals. Ultimately, 214 transgenic petals were regenerated from 24 resistant explants. PCR and GUS quantitative analyses confirmed that these putative transgenic petals have stably overexpressed GUS genes. Furthermore, an RNAi vector of the anthocyanidin 3-O-glucosyltransferase gene (MaGT) was integrated into grape hyacinth petals using the same strategy. Compared with the non-transgenic controls, reduced expression of the MaGT occurred in all transgenic petals, which caused pigmentation loss by repressing anthocyanin accumulation.ConclusionThe Agrobacterium transformation method via petal organogenesis of grape hyacinth took only 3–4 months to implement, and was faster and easier to perform than other gene-overexpressing or -silencing techniques that are currently available.

CsUFO is involved in the formation of flowers and tendrils in cucumber.

An unusual flower and tendril (uft) mutant in cucumber was caused by a mutation in Csa1G056950 encoding an F-box protein. Flowers and tendrils are important agronomic and yield traits of cucumber (Cucumis sativus L.). In this study, we identified an unusual flower and tendril (uft) mutant from an ethyl methanesulfonate (EMS) mutagenesis population. Genetic analysis revealed that the phenotype of the uft mutant was regulated by a single recessive nuclear gene. Map-based cloning and MutMap+ results demonstrated that Csa1G056950 (CsUFO), encoding an F-box protein, was the causal gene for the uft mutant phenotype of cucumber. A single nucleotide polymorphism (SNP) mutation (C to T) in the second exon of CsUFO resulted in premature translation termination. The expression level of CsUFO was significantly decreased in apical buds of the uft mutant compared with the wild-type (WT) WD1. Transcriptome analysis indicated that many genes for organ development were down-regulated in uft plants, suggesting CsUFO-associated networks that regulate flower and tendril development. These findings provide a new insight into understanding the molecular mechanisms of flower organogenesis in cucumber.

Characterization of floral morphoanatomy and identification of marker genes preferentially expressed during specific stages of cotton flower development.

Characterization of anther and ovule developmental programs and expression analyses of stage-specific floral marker genes in Gossypium hirsutum allowed to build a comprehensive portrait of cotton flower development before fiber initiation. Gossypium hirsutum is the most important cotton species that is cultivated worldwide. Although cotton reproductive development is important for fiber production, since fiber is formed on the epidermis of mature ovules, cotton floral development remains poorly understood. Therefore, this work aims to characterize the cotton floral morphoanatomy by performing a detailed description of anther and ovule developmental programs and identifying stage-specific floral marker genes in G. hirsutum. Using light microscopy and scanning electron microscopy, we analyzed anther and ovule development during 11 stages of flower development. To better characterize the ovule development in cotton, we performed histochemical analyses to evaluate the accumulation of phenolic compounds, pectin, and sugar in ovule tissues. After identification of major hallmarks of floral development, three key stages were established in G. hirsutum floral development: in stage 1 (early-EF), sepal, petal, and stamen primordia were observed; in stage 2 (intermediate-IF), primordial ovules and anthers are present, and the differentiating archesporial cells were observed, marking the beginning of microsporogenesis; and in stage 6 (late-LF), flower buds presented initial anther tapetum degeneration and microspore were released from the tetrad, and nucellus and both inner and outer integuments are developing. We used transcriptome data of cotton EF, IF and LF stages to identify floral marker genes and evaluated their expression by real-time quantitative PCR (qPCR). Twelve marker genes were preferentially expressed in a stage-specific manner, including the putative homologs for AtLEAFY, AtAPETALA 3, AtAGAMOUS-LIKE 19 and AtMALE STERILITY 1, which are crucial for several aspects of reproductive development, such as flower organogenesis and anther and petal development. We also evaluated the expression profile of B-class MADS-box genes in G. hirsutum floral transcriptome (EF, IF, and LF). In addition, we performed a comparative analysis of developmental programs between Arabidopsis thaliana and G. hirsutum that considered major morphoanatomical and molecular processes of flower, anther, and ovule development. Our findings provide the first detailed analysis of cotton flower development.

Genome-wide identification and functional analysis of JmjC domain-containing genes in flower development of Rosa chinensis.

We genome-wide identified 28 JmjC domain-containing genes, further spatio-temporal expression profiling and genetic analysis defined them as epigenetic regulators in flowering initiation of Rosa chinensis. The JmjC domain-containing histone demethylases play critical roles in maintaining homeostasis of histone methylations, thus are vital for plant growth and development. Genome-wide identification of the JmjC domain-containing genes have been reported in several species, however, no systematic study has been performed in rose plants. In this paper, we identified 28 JmjC domain-containing genes from the newly published genome database of Rosa chinensis. The JmjC domain-containing proteins in R. chinensis were divided into seven groups, KDM3 was the largest group with 13 members, and JmjC domain-only A and KDM5B were the smallest clades both with only one member. Although all the JmjC domain proteins having a conserved JmjC domain, the gene and protein structure experienced differentiation and specification during the evolution, especially in KDM3 clade, one gene (RcJMJ40) was found carrying site deletions for cofactors Fe (II) and α-KG binding which were crucial for demethylase activities, three genes (RcJMJ41, RcJMJ43 and RcJMJ44) had no intron while two of them had tandem JmjC domains. Spatial expression pattern analysis of these JmjC domain-containing genes in different tissues showed most of them were highly expressed in reproductive tissues such as floral meristem and closed flowers than vegetative tissues, demonstrating their important functions in developmental switch from vegetative to reproductive growth of roses. Temporal expression profiling indicated majority of JmjC domain-containing genes from R. chinensis fluctuated along with floral bud differentiation and development, further proving their essential roles in flower organogenesis. VIGS induced silencing of RcJMJ12 led to delayed flowering time, and decreased the expression levels of flowering integrator such as RcFT, RcSOC1, RcFUL, RcLFY and RcAP1, therefore providing the genetic evidence of RcJMJ12 in flowering initiation. Collectively, spatio-temporal expression profiling and genetic analysis defined the JmjC domain-containing genes as important epigenetic regulators in flower development of R. chinensis.

Multiple microRNAs Regulate the Floral Development and Sex Differentiation in the Dioecious Cucurbit Coccinia grandis (L.) Voigt

Despite having a small genome and heteromorphic sex chromosomes, the molecular basis of sex differentiation in the dioecious cucurbit, Coccinia grandis, largely remains unclear. Increasing evidences indicate a vital regulatory role of microRNAs in the reproductive development of plants. In this study, we used a combination of high-throughput small RNA sequencing and computational analysis to identify sex-specific miRNAomes from male and female buds of C. grandis. Ninety-eight conserved miRNAs from 22 families and 44 novel miRNAs specific to C. grandis were detected. Comparative profiling together with Northern blot and qRT-PCR analysis revealed 41 significantly differentially expressed (DE) miRNAs, of which 16 could be fundamental to the regulation of sexual dimorphism. One hundred six target genes were predicted for 35 DE miRNAs that were significantly involved in flower organogenesis, phytohormone signaling, metabolism, transcription regulation, and DNA methylation. Temporal analysis of a set of 16 target genes at three stages of the bud development revealed a reciprocal alteration in their expression pattern with the complementary miRNAs. Further, the miR167a-1, miR393a, miR398b, and miRn9 mediated down-regulation of four predicted targets associated with reproductive organ development in C. grandis was confirmed through transient co-expression in Nicotiana benthaminana. Taken together, the present study represents the first report suggesting that multiple miRNA-mediated gene silencing cascade could be involved in regulating the molecular basis of sex differentiation in C. grandis.

Linking Terpene Synthases to Sesquiterpene Metabolism in Grapevine Flowers.

Grapevine (Vitis vinifera L.) terpene synthases (VviTPS) are responsible for the biosynthesis of terpenic volatiles. Volatile profiling of nine commercial wine cultivars showed unique cultivar-specific variation in volatile terpenes emitted from grapevine flowers. The flower chemotypes of three divergent cultivars, Muscat of Alexandria, Sauvignon Blanc and Shiraz were subsequently investigated at two flower developmental stages (EL-18 and -26). The cultivars displayed unique flower sesquiterpene compositions that changed during flower organogenesis and the profiles were dominated by either (E)-β-farnesene, (E,E)-α-farnesene or (+)-valencene. In silico remapping of microarray probes to VviTPS gene models allowed for a meta-analysis of VviTPS expression patterns in the grape gene atlas to identify genes that could regulate terpene biosynthesis in flowers. Selected sesquiterpene synthase genes were isolated and functionally characterized in three cultivars. Genotypic differences that could be linked to the function of a targeted gene model resulted in the isolation of a novel and cultivar-specific single product sesquiterpene synthase from Muscat of Alexandria flowers (VvivMATPS10), synthesizing (E)-β-farnesene as its major volatile. Furthermore, we identified structural variations (SNPs, InDels and splice variations) in the characterized VviTPS genes that potentially impact enzyme function and/or volatile sesquiterpene production in a cultivar-specific manner.

Floral meristem size and organ number correlation in Eucryphia (Cunoniaceae).

We present a comparative flower ontogenetic study in five species of the genus Eucryphia with the aim of testing whether differences in the organ number observed can be explained by changes in the meristematic size of floral meristem and floral organs. Species native to Oceania, viz. E. milliganii, E. lucida and E. moorei, have the smallest gynoecia with ca. 6 carpels, while the Chilean E. glutinosa and E. cordifolia present more than ten carpels. E. milliganii has the smallest flower with the lowest stamen number (ca. 50), while the other species produce around 200 stamens and more. Standardized measurements of meristematic sectors were taken in 49 developing flowers that were classified into three well-defined ontogenetic stages. Sizes of meristems varied significantly among species within each developmental stage as revealed by ANOVA analyses. Significant regressions between organ number and corresponding meristem size were consistent with the premise that a larger meristem size prior to organ initiation could be determining for a higher organ number. Flower organogenesis in Eucryphia also involves relevant meristem expansion while the organs are initiated, which results in a particular androecium patterning with a chaotic stamen arrangement. Meristem expansion also appears to be slower but more extensive in species with larger initial meristematic size, suggesting that flower phenotype can be determined in ontogeny by this heterochronic interplay of space and time.

Genetic regulation of maize flower development and sex determination.

The determining process of pistil fate are central to maize sex determination, mainly regulated by a genetic network in which the sex-determining genes SILKLESS 1 , TASSEL SEED 1 , TASSEL SEED 2 and the paramutagenic locus Required to maintain repression 6 play pivotal roles. Maize silks, which emerge from theear shoot and derived from thepistil, are the functional stigmas of female flowers and play a pivotal role in pollination. Previous studies on sex-related mutants have revealed that sex-determining genes and phytohormones play an important role in the regulation of flower organogenesis. The processes determining pistil fate are central to flower development, where a silk identified gene SILKLESS 1 (SK1) is required to protect pistil primordia from a cell death signal produced by two commonly known genes, TASSEL SEED 1 (TS1) and TASSEL SEED 2 (TS2). In this review, maize flower developmental process is presented together with a focus on important sex-determining mutants and hormonal signaling affecting pistil development. The role of sex-determining genes, microRNAs, phytohormones, and the paramutagenic locus Required to maintain repression 6 (Rmr6), in forming a regulatory network that determines pistil fate, is discussed. Cloning SK1 and clarifying its function were crucial in understanding the regulation network of sex determination. The signaling mechanisms of phytohormones in sex determination are also an important research focus.

A sister of PIN1 gene in tomato (Solanum lycopersicum) defines leaf and flower organ initiation patterns by maintaining epidermal auxin flux

The spatiotemporal localization of the plant hormone auxin acts as a positional cue during early leaf and flower organogenesis. One of the main contributors to auxin localization is the auxin efflux carrier PIN-FORMED1 (PIN1). Phylogenetic analysis has revealed that PIN1 genes are split into two sister clades; PIN1 and the relatively uncharacterized Sister-Of-PIN1 (SoPIN1). In this paper we identify entire-2 as a loss-of-function SlSoPIN1a (Solyc10g078370) mutant in Solanum lycopersicum. The entire-2 plants are unable to specify proper leaf initiation leading to a frequent switch from the wild type spiral phyllotactic pattern to distichous and decussate patterns. Leaves in entire-2 are large and less complex and the leaflets display spatial deformities in lamina expansion, vascular development, and margin specification. During sympodial growth in entire-2 the specification of organ position and identity is greatly affected resulting in variable branching patterns on the main sympodial and inflorescence axes. To understand how SlSoPIN1a functions in establishing proper auxin maxima we used the auxin signaling reporter DR5: Venus to visualize differences in auxin localization between entire-2 and wild type. DR5: Venus visualization shows a widening of auxin localization which spreads to subepidermal tissue layers during early leaf and flower organogenesis, showing that SoPIN1 functions to focus auxin signaling to the epidermal layer. The striking spatial deformities observed in entire-2 help provide a mechanistic framework for explaining the function of the SoPIN1 clade in S.lycopersicum.

The ERECTA, CLAVATA and class III HD-ZIP Pathways Display Synergistic Interactions in Regulating Floral Meristem Activities.

In angiosperms, the production of flowers marks the beginning of the reproductive phase. At the emergence of flower primordia on the flanks of the inflorescence meristem, the WUSCHEL (WUS) gene, which encodes a homeodomain transcription factor starts to be expressed and establishes de novo stem cell population, founder of the floral meristem (FM). Similarly to the shoot apical meristem a precise spatial and temporal expression pattern of WUS is required and maintained through strict regulation by multiple regulatory inputs to maintain stem cell homeostasis. However, following the formation of a genetically determined fixed number of floral organs, this homeostasis is shifted towards organogenesis and the FM is terminated. In here we performed a genetic study to test how a reduction in ERECTA, CLAVATA and class III HD-ZIP pathways affects floral meristem activity and flower development. We revealed strong synergistic phenotypes of extra flower number, supernumerary whorls, total loss of determinacy and extreme enlargement of the meristem as compared to any double mutant combination indicating that the three pathways, CLV3, ER and HD-ZIPIII distinctively regulate meristem activity and that they act in parallel. Our findings yield several new insights into stem cell-driven development. We demonstrate the crucial requirement for coupling floral meristem termination with carpel formation to ensure successful reproduction in plants. We also show how regulation of meristem size and alternation in spatial structure of the meristem serve as a mechanism to determine flower organogenesis. We propose that the loss of FM determinacy due to the reduction in CLV3, ER and HD-ZIPIII activity is genetically separable from the AGAMOUS core mechanism of meristem termination.

Transcriptional Analysis of Tendril and Inflorescence Development in Grapevine (Vitis vinifera L.)

In grapevine (Vitis vinifera L.), the lateral meristem can give rise to either tendrils or inflorescences which are determined organs. To get insights into the processes of tendril and inflorescence development, we characterized the transcriptional variation taking place in both organs. The results of the global transcriptional analyses along tendril and inflorescence development suggested that these two homologous organs initially share a common transcriptional program related to cell proliferation and growth functions. In later developmental stages they showed organ specific gene expression programs related to the particular differentiation processes taking place in each organ. In this way, tendrils showed higher transcription of genes related to photosynthesis, hormone signaling and secondary metabolism than inflorescences, while inflorescences displayed higher transcriptional activity for genes encoding transcription factors, mainly those belonging to the MADS-box gene family. The expression profiles of selected transcription factors related with inflorescence and flower meristem identity and with flower organogenesis were generally conserved with respect to their homologs in model species. Regarding tendrils, it was interesting to find that genes related with reproductive development in other species were also recruited for grapevine tendril development. These results suggest a role for those genes in the regulation of basic cellular mechanisms common to both developmental processes.

Sexual Dimorphism Floral MicroRNA Profiling and Target Gene Expression in Andromonoecious Poplar (Populus tomentosa)

Although the molecular basis of poplar sex-specific flower development remains largely unknown, increasing evidence indicates an essential role for microRNAs (miRNAs). The specific miRNA types and precise miRNA expression patterns in dioecious plant flower development remain unclear. Here, we used andromonoecious poplar, an exceptional model system, to eliminate the confounding effects of genetic background of dioecious plants. This system, combined with high-throughput sequencing and computational analysis, allowed us to characterize sex-specific miRNAomes from female and male flowers. Comparative miRNAome analysis combined with quantitative real-time PCR revealed the expression patterns of 27 miRNAs in poplar flower and showed that the targets of these miRNAs are involved in flower organogenesis, Ca2+ transport, phytohormone synthesis and metabolism, and DNA methylation. This paper describes a complex regulatory network consisting of these miRNAs expressed in sex-specific flower development in a dioecious plant. The conserved and novel miRNA locations were annotated in the Populus trichocarpa genome. Among these, miRNA Pto-F70 and 4 targets are located in the sex-determination regions of chromosome XIX. Furthermore, two novel miRNAs, Pto-F47 and Pto-F68, were shown for the first time to be regulatory factors in phytohormone interactions. To our knowledge, this report is the first systematic investigation of sex-specific flower-related miRNAs and their targets in poplar, and it deepens our understanding of the important regulatory functions of miRNAs in female and male flower development in this dioecious plant.

Network function shapes network structure: the case of the Arabidopsis flower organ specification genetic network

The reconstruction of many biological networks has allowed detailed studies of their structural properties. Several features exhibited by these networks have been interpreted to be the result of evolutionary dynamics. For instance the degree distributions may follow from a preferential attachment of new genes to older ones during evolution. Here we argue that even in the absence of any evolutionary dynamics, the presence of atypical features may follow from the fact that the network implements certain functions. To examine this network function shapes network structure scenario, we focus on the Arabidopsis genetic network controlling early flower organogenesis in which gene expression dynamics has been modelled using a Boolean framework. Specifically, for a system with 15 master genes, the phenotype consists of 10 experimentally determined steady-state expression patterns, considered here as the functional constraints on the network. The space of genetic networks satisfying these constraints is sometimes referred to as the neutral or genotype network. We sample this space using Markov Chain Monte Carlo which allows us to demonstrate how the functional (phenotypic) constraints shape the gene network structure. We find that this shaping is strongest for the edge (interaction) usage, with effects that are functionally interpretable. In contrast, higher order features such as degree assortativity and network motifs are hardly shaped by the phenotypic constraints.