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Summary: Grain weight is an important determinant of grain yield. However, the underlying regulatory mechanisms for grain size remain to be fully elucidated. Here, we identify a rice mutant grain weight 9 (gw9), which exhibits larger and heavier grains due to excessive cell proliferation and expansion in spikelet hull. GW9 encodes a nucleus‐localized protein containing both C2H2 zinc finger (C2H2‐ZnF) and VRN2‐EMF2‐FIS2‐SUZ12 (VEFS) domains, serving as a negative regulator of grain size and weight. Interestingly, the non‐frameshift mutations in C2H2‐ZnF domain result in increased plant height and larger grain size, whereas frameshift mutations in both C2H2‐ZnF and VEFS domains lead to dwarf and malformed spikelet. These observations indicated the dual functions of GW9 in regulating grain size and floral organ identity through the C2H2‐ZnF and VEFS domains, respectively. Further investigation revealed the interaction between GW9 and the E3 ubiquitin ligase protein GW2, with GW9 being the target of ubiquitination by GW2. Genetic analyses suggest that GW9 and GW2 function in a coordinated pathway controlling grain size and weight. Our findings provide a novel insight into the functional role of GW9 in the regulation of grain size and weight, offering potential molecular strategies for improving rice yield. [ABSTRACT FROM AUTHOR]

Abstract Background Lonicera japonica Thunb. is widely used in traditional Chinese medicine. Medicinal L. japonica mainly consists of dried flower buds and partially opened flowers, thus flowers are an important quality indicator. MADS-box genes encode transcription factors that regulate flower development. However, little is known about these genes in L. japonica. Results In this study, 48 MADS-box genes were identified in L. japonica, including 20 Type-I genes (8 Mα, 2 Mβ, and 10 Mγ) and 28 Type-II genes (26 MIKCc and 2 MIKC*). The Type-I and Type-II genes differed significantly in gene structure, conserved domains, protein structure, chromosomal distribution, phylogenesis, and expression pattern. Type-I genes had a simpler gene structure, lacked the K domain, had low protein structure conservation, were tandemly distributed on the chromosomes, had more frequent lineage-specific duplications, and were expressed at low levels. In contrast, Type-II genes had a more complex gene structure; contained conserved M, I, K, and C domains; had highly conserved protein structure; and were expressed at high levels throughout the flowering period. Eleven floral homeotic MADS-box genes that are orthologous to the proposed Arabidopsis ABCDE model of floral organ identity determination, were identified in L. japonica. By integrating expression pattern and protein interaction data for these genes, we developed a possible model for floral organ identity determination. Conclusion This study genome-widely identified and characterized the MADS-box gene family in L. japonica. Eleven floral homeotic MADS-box genes were identified and a possible model for floral organ identity determination was also developed. This study contributes to our understanding of the MADS-box gene family and its possible involvement in floral organ development in L. japonica.

Background: Lonicera japonica Thunb. is widely used in traditional Chinese medicine. Medicinal L. japonica mainly consists of dried flower buds and partially opened flowers, thus flowers are an important quality indicator. MADS-box genes encode transcription factors that regulate flower development. However, little is known about these genes in L. japonica. Results: In this study, 48 MADS-box genes were identified in L. japonica, including 20 Type-I genes (8 Mα, 2 Mβ, and 10 Mγ) and 28 Type-II genes (26 MIKCc and 2 MIKC*). The Type-I and Type-II genes differed significantly in gene structure, conserved domains, protein structure, chromosomal distribution, phylogenesis, and expression pattern. Type-I genes had a simpler gene structure, lacked the K domain, had low protein structure conservation, were tandemly distributed on the chromosomes, had more frequent lineage-specific duplications, and were expressed at low levels. In contrast, Type-II genes had a more complex gene structure; contained conserved M, I, K, and C domains; had highly conserved protein structure; and were expressed at high levels throughout the flowering period. Eleven floral homeotic MADS-box genes that are orthologous to the proposed Arabidopsis ABCDE model of floral organ identity determination, were identified in L. japonica. By integrating expression pattern and protein interaction data for these genes, we developed a possible model for floral organ identity determination. Conclusion: This study genome-widely identified and characterized the MADS-box gene family in L. japonica. Eleven floral homeotic MADS-box genes were identified and a possible model for floral organ identity determination was also developed. This study contributes to our understanding of the MADS-box gene family and its possible involvement in floral organ development in L. japonica. [ABSTRACT FROM AUTHOR]

One of the most important divisions in the plant kingdom is the monocotyledon division of angiosperms. More than 60,000 monocot spp. have been identified, the majority of which are economically important, such as the Poaceae, Orchidaceae, Arecaceae, Liliaceae, and certain other families. The involvement of the ABCDE model of floral organ determination during flower development is a growing area of research in the field of molecular biology due to the diversity in the floral morphology of monocots. The MADS-box gene family is a large molecular transcript family that helps identify specific proteins involved in floral development. It is classified into several classes based on its function. The review aimed to evaluate the significance of ABCDE genes for floral development and subsequent organ identification, which have been discovered in a range of monocot plants, as well as the functions of these genes in determining the sex of dioecious plants. We sought to summarise the MADS-box gene responsible for flower initiation and floral whorl differentiation reported in economically valuable monocotyledonous plants.

One of the most important divisions in the plant kingdom is the monocotyledon division of angiosperms. More than 60,000 monocot spp. have been identified, the majority of which are economically important, such as the Poaceae, Orchidaceae, Arecaceae, Liliaceae, and certain other families. The involvement of the ABCDE model of floral organ determination during flower development is a growing area of research in the field of molecular biology due to the diversity in the floral morphology of monocots. The MADS-box gene family is a large molecular transcript family that helps identifies specific proteins involved in floral development. It is classified into several classes based on its function. The review aimed to evaluate the significance of ABCDE genes for floral development and subsequent organ identification, which have been discovered in a range of monocot plants, as well as the functions of these genes in determining the sex of dioecious plants. We sought to summarise the MADSbox gene responsible for flower initiation and floral whorl differentiation reported in economically valuable monocotyledonous plants. [ABSTRACT FROM AUTHOR]

Floral organ development and regulation of flowering time in rice is closely associated with MADS-box transcriptional factors (TFs). MADS-box proteins contain a conserved 60 amino acid MADS-box motif for a sequence-specific DNA-binding activity that also functions in dimerization and accessory factor binding. A systematic understanding of this MADS-box TF subfamily is needed to explain the functional complexity among the gene family members. In total, the function of 33 out of 75 MADS-box TFs in rice has been characterized. Meta-anatomical expression data based on a large collection of spatiotemporal microarray data integrated to the phylogenetic tree context was very effective at explaining the functional complexity or specificity among a large gene family. Subsequently, a cluster of MADS-box TFs consisting of 15 gene members showed preferred expression in floral organs, and their expression patterns are well correlated with previously identified functions in floral organ identity. In addition, the hierarchical structure of a group of MADS-box TFs, based on the expression patterns, was well supported by the genetic studies. OsMADS1 functions in the earliest step of floral organ development and affects the overall floral organ development by identifying downregulation of nine members in the same clade in osmads1 mutant and observed phenotypic changes. The combination of hierarchical structure and possible hetero-dimerization among MADS-box TFs allows for understanding the molecular and genetic regulatory model for floral organ development in rice. This work provides a comprehensive understanding of the functions of MADS-box TFs and will be a useful guide for further studies. [ABSTRACT FROM AUTHOR]

Abstract Background Flower development directly affects fruit production in tomato. Despite the framework mediated by ABC genes have been established in Arabidopsis, the spatiotemporal precision of floral development in tomato has not been well examined. Results Here, we analyzed a novel tomato stamenless like flower (slf) mutant in which the development of stamens and carpels is disturbed, with carpelloid structure formed in the third whorl and ectopic formation of floral and shoot apical meristem in the fourth whorl. Using bulked segregant analysis (BSA), we assigned the causal mutation to the gene Solanum lycopersicum GT11 (SlGT11) that encodes a transcription factor belonging to Trihelix gene family. SlGT11 is expressed in the early stages of the flower and the expression becomes more specific to the primordium position corresponding to stamens and carpels in later stages of the floral development. Further RNAi silencing of SlGT11 verifies the defective phenotypes of the slf mutant. The carpelloid stamen in slf mutant indicates that SlGT11 is required for B-function activity in the third whorl. The failed termination of floral meristem and the occurrence of floral reversion in slf indicate that part of the C-function requires SlGT11 activity in the fourth whorl. Furthermore, we find that at higher temperature, the defects of slf mutant are substantially enhanced, with petals transformed into sepals, all stamens disappeared, and the frequency of ectopic shoot/floral meristem in fourth whorl increased, indicating that SlGT11 functions in the development of the three inner floral whorls. Consistent with the observed phenotypes, it was found that B, C and an E-type MADS-box genes were in part down regulated in slf mutants. Conclusions Together with the spatiotemporal expression pattern, we suggest that SlGT11 functions in floral organ patterning and maintenance of floral determinacy in tomato.

Background: APETALA3 (AP3) has significant roles in petal and stamen development in accordance with the classical ABC model. Results: The AP3 homolog, CDM19, from Chrysanthemum morifolium cv. Jinba was cloned and sequenced. Sequence and phylogenetic analyses revealed that CDM19 is of DEF/AP3 lineage possessing the characteristic MIKC-type II structure. Expression analysis showed that CDM19 was transcribed in petals and stamens of ray and disc florets with weak expression in the carpels. Ectopic expression of CDM19 in Arabidopsis wild-type background altered carpel development resulting in multi-carpel siliques. CDM19 could only partially rescue the Arabidopsis ap3‐–3 mutant. Conclusions: Our results suggest that CDM19 may partially be involved in petal and stamen development in addition to having novel function in carpel development.How to cite: Githeng’u SK, Ding L, Zhao K, et al. Ectopic expression of Chrysanthemum CDM19 in Arabidopsis reveals a novel function in carpel development. Electron J Biotechnol 2020;45. https://doi.org/10.1016/j.ejbt.2020.03.001.

Arabidopsis flower primordia give rise to organ primordia in stereotypical positions within four concentric whorls. Floral organ primordia in each whorl undergo distinct developmental programs to become one of four organ types (sepals, petals, stamens, and carpels). The Arabidopsis transcription factors AINTEGUMENTA (ANT) and AINTEGUMENTA-LIKE6 (AIL6) are required for correct positioning of floral organ initiation, contribute to the specification of floral organ identity, and regulate the growth and morphogenesis of developing floral organs. To gain insight into the molecular mechanisms by which ANT and AIL6 contribute to floral organogenesis, we identified the genome-wide binding sites of both ANT and AIL6 in stage 3 flower primordia, the developmental stage at which sepal primordia become visible and class B and C floral homeotic genes are first expressed. AIL6 binds to a subset of ANT sites, suggesting that AIL6 regulates some but not all of the same target genes as ANT. ANT- and AIL6-binding sites are associated with genes involved in many biological processes related to meristem and flower organ development. Comparison of genes associated with both ANT and AIL6 ChIP-Seq peaks and those differentially expressed after perturbation of ANT and/or AIL6 activity identified likely direct targets of ANT and AIL6 regulation. These include class B and C floral homeotic genes, growth regulatory genes, and genes involved in vascular development. [ABSTRACT FROM AUTHOR]

Within the MADS-box gene family, the AGAMOUS-subfamily genes are particularly important for plant reproduction, because they control stamen and carpel identity. A number of studies in the last three decades have demonstrated that the AGAMOUS (AG) function has been conserved during land plant evolution. However, gene duplication events have led to subfunctionalization and neofunctionalization of AG-like genes in many species. Here we show that alternative splicing in Oryza sativa produces two variants of the AG ortholog OsMADS3 which differ in just one serine residue, S109. Interestingly, this alternative splicing variant is conserved and specific to the grass family. Since in eudicots the S109 residue is absent in AG proteins, stamen and carpel identity determination activity of the two rice isoforms was tested in Arabidopsis thaliana. These experiments revealed that only the eudicot-like OsMADS3 isoform, lacking the serine residue, had ability to specify stamens and carpels in ag mutant flowers, suggesting an important functional role for the serine residue at position 109 in AG proteins of grasses.

Main conclusion: A new, stable, null mutant of OsMADS1 generated by homologous recombination-based gene targeting in an indica rice confirms its regulatory role for floral meristem identity, its determinate development and floral organ differentiation. OsMADS1, an E-class MADS-box gene, is an important regulator of rice flower development. Studies of several partial loss-of-function and knockdown mutants show varied floret organ defects and degrees of meristem indeterminacy. The developmental consequences of a true null mutant on floret meristem identity, its determinate development and differentiation of grass-specific organs such as the lemma and palea remain unclear. In this study, we generated an OsMADS1 null mutant by homologous recombination-mediated gene targeting by inserting a selectable marker gene (hpt) in OsMADS1 and replacing parts of its cis-regulatory and coding sequences. A binary vector was constructed with diphtheria toxin A chain gene (DT-A) as a negative marker to eliminate random integrations and the hpt marker for positive selection of homologous recombination. Precise disruption of the endogenous OsMADS1 locus in the rice genome was confirmed by Southern hybridization. The homozygous osmads1ko null mutant displayed severe defects in all floral organs including the lemma and palea. We also noticed striking instances of floral reversion to inflorescence and vegetative states which has not been reported for other mutant alleles of OsMADS1 and further reinforces the role of OsMADS1 in controlling floral meristem determinacy. Our data suggest, OsMADS1 commits and maintains determinate floret development by regulating floral meristem termination, carpel and ovule differentiation genes (OsMADS58, OsMADS13) while its modulation of genes such as OsMADS15, OsIG1 and OsMADS32 could be relevant in the differentiation and development of palea. Further, our study provides an important perspective on developmental stage-dependent modulation of some OsMADS1 target genes. [ABSTRACT FROM AUTHOR]

Background: Flower development directly affects fruit production in tomato. Despite the framework mediated by ABC genes have been established in Arabidopsis, the spatiotemporal precision of floral development in tomato has not been well examined. Results: Here, we analyzed a novel tomato stamenless like flower (slf) mutant in which the development of stamens and carpels is disturbed, with carpelloid structure formed in the third whorl and ectopic formation of floral and shoot apical meristem in the fourth whorl. Using bulked segregant analysis (BSA), we assigned the causal mutation to the gene Solanum lycopersicum GT11 (SlGT11) that encodes a transcription factor belonging to Trihelix gene family. SlGT11 is expressed in the early stages of the flower and the expression becomes more specific to the primordium position corresponding to stamens and carpels in later stages of the floral development. Further RNAi silencing of SlGT11 verifies the defective phenotypes of the slf mutant. The carpelloid stamen in slf mutant indicates that SlGT11 is required for B-function activity in the third whorl. The failed termination of floral meristem and the occurrence of floral reversion in slf indicate that part of the C-function requires SlGT11 activity in the fourth whorl. Furthermore, we find that at higher temperature, the defects of slf mutant are substantially enhanced, with petals transformed into sepals, all stamens disappeared, and the frequency of ectopic shoot/floral meristem in fourth whorl increased, indicating that SlGT11 functions in the development of the three inner floral whorls. Consistent with the observed phenotypes, it was found that B, C and an E-type MADS-box genes were in part down regulated in slf mutants. Conclusions: Together with the spatiotemporal expression pattern, we suggest that SlGT11 functions in floral organ patterning and maintenance of floral determinacy in tomato. [ABSTRACT FROM AUTHOR]

The question of the origin of petals has long been debated in the botanical literature. Ranunculales are characterized by a spectacular floral diversity, particularly at the perianth level. Recent progress in understanding the genetic bases of floral organ identity suggests a single origin for petals in Ranunculaceae, contrasting with the traditional morphological hypothesis of repeated evolution. However, perianth evolution at the ordinal level remains incompletely understood. Recent advances in the elucidation of phylogenetic relationships in the order now provide a new opportunity to study character evolution with model-based methods. We used ancestral state reconstruction methods that take into account various sources of uncertainty to reconstruct the evolution of floral traits at the scale of Ranunculales using a consensus phylogenetic framework of 144 terminal species representing all families in the order. Ancestrally, Ranunculales probably had three trimerous whorls of perianth organs differentiated into two categories of petaloid organs differing in their shape. Each whorl was further lost or duplicated. Moreover, our results support the hypothesis of a single origin of highly specialized (elaborate) nectariferous petals in Ranunculaceae. [ABSTRACT FROM AUTHOR]

Background and Aims The ranunculid model system Aquilegia is notable for the presence of a fifth type of floral organ, the staminode, which appears to be the result of sterilization and modification of the two innermost whorls of stamens. Previous studies have found that the genetic basis for the identity of this new organ is the result of sub- and neofunctionalization of floral organ identity gene paralogues; however, we do not know the extent of developmental and molecular divergence between stamens and staminodes. Methods We used histological techniques to describe the development of the Aquilegia coerulea 'Origami' staminode relative to the stamen filament. These results have been compared with four other Aquilegia species and the closely related genera Urophysa and Semiaquilegia. As a complement, RNA sequencing has been conducted at two developmental stages to investigate the molecular divergence of the stamen filaments and staminodes in A. coerulea 'Origami'. Key Results Our developmental study has revealed novel features of staminode development, most notably a physical interaction along the lateral margin of adjacent organs that appears to mediate their adhesion. In addition, patterns of abaxial/adaxial differentiation are observed in staminodes but not stamen filaments, including asymmetric lignification of the adaxial epidermis in the staminodes. The comparative transcriptomics are consistent with the observed lignification of staminodes and indicate that stamen filaments are radialized due to overexpression of adaxial identity, while the staminodes are expanded due to the balanced presence of abaxial identity. Conclusions These findings suggest a model in which the novel staminode identity programme interacts with the abaxial/adaxial identity pathways to produce two whorls of laterally expanded organs that are highly differentiated along their abaxial/adaxial axis. While the ecological function of Aquilegia staminodes remains to be determined, these data are consistent with a role in protecting the early carpels from herbivory and/or pathogens. [ABSTRACT FROM AUTHOR]

Within the MADS-box gene family, the AGAMOUS -subfamily genes are particularly important for plant reproduction, because they control stamen and carpel identity. A number of studies in the last three decades have demonstrated that the AGAMOUS (AG) function has been conserved during land plant evolution. However, gene duplication events have led to subfunctionalization and neofunctionalization of AG -like genes in many species. Here we show that alternative splicing in Oryza sativa produces two variants of the AG ortholog OsMADS3 which differ in just one serine residue, S109. Interestingly, this alternative splicing variant is conserved and specific to the grass family. Since in eudicots the S109 residue is absent in AG proteins, stamen and carpel identity determination activity of the two rice isoforms was tested in Arabidopsis thaliana. These experiments revealed that only the eudicot-like OsMADS3 isoform, lacking the serine residue, had ability to specify stamens and carpels in ag mutant flowers, suggesting an important functional role for the serine residue at position 109 in AG proteins of grasses. [ABSTRACT FROM AUTHOR]

Cucumber is an important vegetable crop bearing fleshy pepo fruit harvested immature. Fruits left unpicked in time during summer production, as well as unfavorable environmental conditions during post-harvest shelf, will cause cucumber fruits to turn yellow and ripen, and thus impair the market value. Identification of maturity-related genes is of great agricultural and economic importance for cucumber production. Here, we isolated and characterized a MADS-box gene, Cucumis sativus SHATTERPROOF (CsSHP) in cucumber. Expression analysis indicated that CsSHP was specifically enriched in reproductive organs including stamens and carpels. Ectopic expression of CsSHP was unable to rescue the indehiscence silique phenotype of shp1 shp2 mutant plant in Arabidopsis. Instead, overexpression of CsSHP resulted in early flowering, precocious phenotypes, and capelloid organs in wild-type Arabidopsis. Biochemical analysis indicated that CsSHP directly interacted with cucumber SEPALLATA (SEP) proteins. CsSHP expression increased significantly during the yellowing stage of cucumber ripening, and was induced by exogenous application of abscisic acid (ABA). Therefore, CsSHP may participate in fruit maturation through the ABA pathway and floral organ specification via interaction with CsSEPs to form protein complex in cucumber.

Cucumber is an important vegetable crop bearing fleshy pepo fruit harvested immature. Fruits left unpicked in time during summer production, as well as unfavorable environmental conditions during post-harvest shelf, will cause cucumber fruits to turn yellow and ripen, and thus impair the market value. Identification of maturity-related genes is of great agricultural and economic importance for cucumber production. Here, we isolated and characterized a MADS-box gene, Cucumis sativus SHATTERPROOF (CsSHP) in cucumber. Expression analysis indicated that CsSHP was specifically enriched in reproductive organs including stamens and carpels. Ectopic expression of CsSHP was unable to rescue the indehiscence silique phenotype of shp1 shp2 mutant plant in Arabidopsis. Instead, overexpression of CsSHP resulted in early flowering, precocious phenotypes, and capelloid organs in wild-type Arabidopsis. Biochemical analysis indicated that CsSHP directly interacted with cucumber SEPALLATA (SEP) proteins. CsSHP expression increased significantly during the yellowing stage of cucumber ripening, and was induced by exogenous application of abscisic acid (ABA). Therefore, CsSHP may participate in fruit maturation through the ABA pathway and floral organ specification via interaction with CsSEPs to form protein complex in cucumber. [ABSTRACT FROM AUTHOR]

Metabolomes comprise constitutive and non-constitutive metabolites produced due to physiological, genetic or environmental effects. However, finding constitutive metabolites and non-constitutive metabolites in large datasets is technically challenging. We developed gcProfileMakeR, an R package using standard Excel output files from an Agilent Chemstation GC-MS for automatic data analysis using CAS numbers. gcProfileMakeR has two filters for data preprocessing removing contaminants and low-quality peaks. The first function NormalizeWithinFiles, samples assigning retention times to CAS. The second function NormalizeBetweenFiles, reaches a consensus between files where compounds in close retention times are grouped together. The third function getGroups, establishes what is considered as Constitutive Profile, Non-constitutive by Frequency i.e., not present in all samples and Non-constitutive by Quality. Results can be plotted with the plotGroup function. We used it to analyse floral scent emissions in four snapdragon genotypes. These included a wild type, Deficiens nicotianoides and compacta affecting floral identity and RNAi:AmLHY targeting a circadian clock gene. We identified differences in scent constitutive and non-constitutive profiles as well as in timing of emission. gcProfileMakeR is a very useful tool to define constitutive and non-constitutive scent profiles. It also allows to analyse genotypes and circadian datasets to identify differing metabolites.

Ranunculales, the sister group to all other eudicots, encompasses species with a remarkable floral diversity, which are currently emerging as new model organisms to address questions relating to the genetic architecture of flower morphology and its evolution. These questions concern either traits only found in members of the Ranunculales or traits that have convergently evolved in other large clades of flowering plants.Wepresent recent results obtained on floral organ identity and number, symmetry evolution and spur formation in Ranunculales species. We discuss benefits and future prospects of evo-devo studies in Ranunculales, which can provide the opportunity to decipher the genetic architecture of novel floral traits and also to appraise the degree of conservation of genetic mechanisms involved in homoplasious traits. [ABSTRACT FROM AUTHOR]

The molecular and genetic networks underlying the determination of floral organ identity are well studied, but much less is known about how the flower is partitioned into four developmentally distinct whorls. The SUPERMAN gene is required for proper specification of the boundary between stamens in whorl 3 and carpels in whorl 4, as superman mutants exhibit supernumerary stamens but usually lack carpels. However, it has remained unclear whether extra stamens in superman mutants originate from an organ identity change in whorl 4 or the overproliferation of whorl 3. Using live confocal imaging, we show that the extra stamens in superman mutants arise from cells in whorl 4, which change their fate from female to male, while floral stem cells proliferate longer, allowing for the production of additional stamens. [ABSTRACT FROM AUTHOR]

Arabidopsis, flower development, flower meristem, boundary formation, floral organ identity, APETALA3, SUPERMAN. [Extracted from the article]

During reproductive development, rice plants develop unique flower organs which determine the final grain yield. OsMADS1 , one of SEPALLATA -like MADS-box genes, has been unraveled to play critical roles in rice floral organ identity specification and floral meristem determinacy. However, the molecular mechanisms underlying interactions of OsMADS1 with other floral homeotic genes in regulating flower development remains largely elusive. In this work, we studied the genetic interactions of OsMADS1 with B-, C-, and D-class genes along with physical interactions among their proteins. We show that the physical and genetic interactions between OsMADS1 and OsMADS3 are essential for floral meristem activity maintenance and organ identity specification; while OsMADS1 physically and genetically interacts with OsMADS58 in regulating floral meristem determinacy and suppressing spikelet meristem reversion. We provided important genetic evidence to support the neofunctionalization of two rice C-class genes ( OsMADS3 and OsMADS58 ) during flower development. Gene expression profiling and quantitative RT-PCR analyses further revealed that OsMADS1 affects the expression of many genes involved in floral identity and hormone signaling, and chromatin immunoprecipitation (ChIP)–PCR assay further demonstrated that OsMADS17 is a direct target gene of OsMADS1. Taken together, these results reveal that OsMADS1 has diversified regulatory functions in specifying rice floral organ and meristem identity, probably through its genetic and physical interactions with different floral homeotic regulators. [ABSTRACT FROM AUTHOR]

Love-in-a-mist ( Nigella damascena) is an annual species of Ranunculaceae native to the Mediterranean Basin, characterized by delicate flowers lying on long lacy bracts. Two floral morphs of N. damascena, designated [ P] and [ T], differ in the identity and number of perianth organs and in the position of the perianth-androecium boundary on the meristem. They both occur in the wild. Here we describe a precise comparative schedule of floral development in the two morphs. We divided the sequence of developmental events affecting the floral meristem into six stages and related them to the height of the elongating stem and to the time elapsed after the beginning of stem elongation. In addition, we characterized the expression pattern of C-class genes in floral organs of both morphs in an attempt to better characterize the differences between the two floral groundplans. In the [ T] morph an expansion of the expression domain of AGAMOUS ( AG) paralogues outside the fertile organs was observed, correlating with the change in identity of the inner perianth organs. Expression of AG-like genes in the sepal-like organs suggests these are not identical to true sepals at the molecular level. The morpho-temporal framework we have defined will allow us to compare various gene expression profiles at targeted developmental stages in both morphs, providing further insight into the molecular control of the floral dimorphism in N. damascena and into the processes underlying the transition from a differentiated (bipartite) to an undifferentiated (unipartite) perianth. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178, 608-619. [ABSTRACT FROM AUTHOR]

OsMADS32 is a monocot specific MIKCc type MADS-box gene that plays an important role in regulating rice floral meristem and organs identity, a crucial process for reproductive success and rice yield. However, its underlying mechanism of action remains to be clarified. Here, we characterized a hypomorphic mutant allele of OsMADS32/CFO1, cfo1-3 and identified its function in controlling rice flower development by bioinformatics and protein-protein interaction analysis. The cfo1-3 mutant produces defective flowers, including loss of lodicule identity, formation of ectopic lodicule or hull-like organs and decreased stamen number, mimicking phenotypes related to the mutation of B class genes. Molecular characterization indicated that mis-splicing of OsMADS32 transcripts in the cfo1-3 mutant resulted in an extra eight amino acids in the K-domain of OsMADS32 protein. By yeast two hybrid and bimolecular fluorescence complementation assays, we revealed that the insertion of eight amino acids or deletion of the internal region in the K1 subdomain of OsMADS32 affects the interaction between OsMADS32 with PISTILLATA (PI)-like proteins OsMADS2 and OsMADS4. This work provides new insight into the mechanism by which OsMADS32 regulates rice lodicule and stamen identity, by interaction with two PI-like proteins via its K domain. [ABSTRACT FROM AUTHOR]

Floral organ specification is controlled by various MADS-box genes in both dicots and monocots, whose expression is often subjected to both genetic and epigenetic regulation in Arabidopsis thaliana. However, little information is known about the role of epigenetic modification of MADS-box genes during rice flower development. Here, we report the characterization of a rice gene, CURVED CHIMERIC PALEA 1 ( CCP1) that functions in palea development. Mutation in CCP1 resulted in abnormal palea with ectopic stigmatic tissues and other pleiotropic phenotypes. We found that Os MADS58, a C-class gene responsible for carpel morphogenesis, was ectopically expressed in the ccp1 palea, indicating that the ccp1 palea was misspecified and partially acquired carpel-like identity. Constitutive expression of Os MADS58 in the wild-type rice plants caused morphological abnormality of palea similar to that of ccp1, whereas Os MADS58 knockdown by RNAi in ccp1 could rescue the abnormal phenotype of mutant palea, suggesting that the repression of Os MADS58 expression by CCP1 is critical for palea development. Map-based cloning revealed that CCP1 encodes a putative plant-specific EMBRYONIC FLOWER1 ( EMF1)-like protein. Chromatin immunoprecipitation assay showed that the level of the H3K27me3 at the Os MADS58 locus was greatly reduced in ccp1 compared with that in the wild-type. Taken together, our results show that CCP1 plays an important role in palea development through maintaining H3K27me3-mediated epigenetic silence of the carpel identity-specifying gene Os MADS58, shedding light on the epigenetic mechanism in floral organ development. [ABSTRACT FROM AUTHOR]

Flower development is the process leading from a reproductive meristem to a mature flower with fully developed floral organs. This multi-step process is complex and involves thousands of genes in intertwined regulatory pathways; navigating through the FLOR-ID website will give an impression of this complexity and of the astonishing amount of work that has been carried on the topic (Bouché et al., Nucleic Acids Res 44:D1167-D1171, 2016). Our understanding of flower development mostly comes from the model species Arabidopsis thaliana, but numerous other studies outside of Brassicaceae have helped apprehend the conservation of these mechanisms in a large evolutionary context (Moyroud and Glover, Curr Biol 27:R941-R951, 2017; Smyth, New Phytol 220:70-86, 2018; Soltis et al., Ann Bot 100:155-163, 2007). Integrating additional species and families to the research on this topic can only advance our understanding of flower development and its evolution.In this chapter, we review the contribution that the Solanaceae family has made to the comprehension of flower development. While many of the general features of flower development (i.e., the key molecular players involved in flower meristem identity, inflorescence architecture or floral organ development) are similar to Arabidopsis, our main objective in this chapter is to highlight the points of divergence and emphasize specificities of the Solanaceae. We will not discuss the large topics of flowering time regulation, inflorescence architecture and fruit development, and we will restrict ourselves to the mechanisms included in a time window after the floral transition and before the fertilization. Moreover, this review will not be exhaustive of the large amount of work carried on the topic, and the choices that we made to describe in large details some stories from the literature are based on the soundness of the functional work performed, and surely as well on our own preferences and expertise.First, we will give a brief overview of the Solanaceae family and some of its specificities. Then, our focus will be on the molecular mechanisms controlling floral organ identity, for which extended functional work in petunia led to substantial revisions to the famous ABC model. Finally, after reviewing some studies on floral organ initiation and growth, we will discuss floral organ maturation, using the examples of the inflated calyx of the Chinese lantern Physalis and petunia petal pigmentation., (© 2023. Springer Science+Business Media, LLC, part of Springer Nature.)

Flowering transition and floral organ development influence plant propagation and crop yield. Polycomb-group (PcG) gene EMF2 restrains flowering by suppressing floral organ identity genes as an epigenetic regulator in Arabidopsis. Here, we identified that OsEMF2b, a homologue of EMF2, acted as a regulator of flowering transition and floral organ identity in rice. The OsEMF2b T-DNA insertion mutations and RNA interference transgenic plants cause late flowering, whereas OsEMF2b overexpressing lines result in early flowering. The transcript levels of genes involved in rice flowering pathway differ in wild-type plants and osemf2b mutants. The transcripts of Ehd1, Hd3a, and RFT1 decrease, whereas the expression level of OsLFL1 increases in the osemf2b mutants under short-day and long-day conditions. These results indicated that OsEMF2b functioned as the upregulator of Ehd1, Hd3a, and RFT1 and the downregulator of OsLFL1 during floral induction. Quantitative RT-PCR assay indicated that OsEMF2b regulated the transcript levels of floral homeotic A-, B-, C-, D-, and E-class genes and participated in floral organ development in rice. Chromatin immunoprecipitation analyses showed that OsEMF2b was directly associated with OsLFL1 and OsMADS4, such that the H3K27me3 was enriched on these target genes chromatin in WT but not in the OsEMF2b RNAi plants. Our results demonstrate that OsEMF2b promotes flowering through direct suppressing of the OsLFL1 expression (a suppressor of flowering) via a mechanism distinct from Arabidopsis. [ABSTRACT FROM AUTHOR]

Background: The production of heather (Calluna vulgaris) in Germany is highly dependent on cultivars with mutated flower morphology, the so-called diplocalyx bud bloomers. So far, this unique flower type of C. vulgaris has not been reported in any other plant species. The flowers are characterised by an extremely extended flower attractiveness, since the flower buds remain closed throughout the complete flowering season. The flowers of C. vulgaris bud bloomers are male sterile, because the stamens are absent. Furthermore, petals are converted into sepals. Therefore the diplocalyx bud bloomer flowers consist of two whorls of sepals directly followed by the gynoecium. Results: A broad comparison was undertaken to identify genes differentially expressed in the bud flowering phenotype and in the wild type of C. vulgaris. Transcriptome sequence reads were generated using 454 sequencing of two flower type specific cDNA libraries. In total, 360,000 sequence reads were obtained, assembled to 12,200 contigs, functionally mapped, and annotated. Transcript abundances were compared and 365 differentially expressed genes detected. Among these differentially expressed genes, Calluna vulgaris PISTILLATA (CvPI) which is the orthologue of the Arabidopsis B gene PISTILLATA (PI) was considered as the most promising candidate gene. Quantitative Reverse Transcription Polymerase Chain Reaction (qRT PCR) was performed to analyse the gene expression levels of two C. vulgaris B genes CvPI and Calluna vulgaris APETALA 3 (CvAP3) in both flower types. CvAP3 which is the orthologue of the Arabidopsis B gene APETALA 3 (AP3) turned out to be ectopically expressed in sepals of wild type and bud bloomer flowers. CvPI expression was proven to be reduced in the bud blooming flowers. Conclusions: Differential expression patterns of the B-class genes CvAP3 and CvPI were identified to cause the characteristic morphology of C. vulgaris flowers leading to the following hypotheses: ectopic expression of CvAP3 is a convincing explanation for the formation of a completely petaloid perianth in both flower types. In C. vulgaris, CvPI is essential for determination of petal and stamen identity. The characteristic transition of petals into sepals potentially depends on the observed deficiency of CvPI and CvAP3 expression in bud blooming flowers. [ABSTRACT FROM AUTHOR]

Abstract: We cloned 10 Japanese pear (Pyrus pyrifolia) MIKC-type II MADS-box genes, and analyzed their expression during fruit development and ripening. PpMADS2-1 was APETALA (AP)1-like; PpMADS3-1 was FRUITFULL (FUL)/SQUAMOSA (SQUA)-like; PpMADS4-1 was AGAMOUS-like (AGL)6; PpMADS5-1 and PpMADS8-1 were SUPPRESSOR OF OVEREXPRESSION OF CONSTANS (SOC)-like; PpMADS9-1, PpMADS12-1, PpMADS14-1 and PpMADS16-1 were SEPALLATA (SEP)-like; while PpMADS15-1 was AGL/SHATTERPROOF (SHP)-like. Phylogenetic analysis showed their grouping into five major clades (and 10 sub-clades) that was consistent with their diverse functional types. Expression analysis in flower tissue revealed their distinct putative homeotic functional classes: A-class (PpMADS2-1, PpMADS3-1, PpMADS4-1, and PpMADS14-1), C-class (PpMADS15-1), E-class (PpMADS9-1, PpMADS12-1, and PpMADS16-1) and E (F)-class (PpMADS5-1 and PpMADS8-1). Differential gene expression was observed in different fruit tissues (skin, cortex and core) as well as in the cortex during the course of fruit development and ripening. Collectively, our results suggest their involvement in the diverse aspects of plant development including flower development and the course of fruit development and ripening. [Copyright &y& Elsevier]

Development of the epidermis involves members of the class- IV homeodomain-leucine zipper ( HD- ZIP IV) transcription factors. The Arabidopsis HD- ZIP IV family consists of 16 members, among which PROTODERMAL FACTOR 2 ( PDF2) and ARABIDOPSIS THALIANA MERISTEM LAYER 1 ( ATML1) play an indispensable role in the differentiation of shoot epidermal cells; however, the functions of other HD- ZIP IV genes that are also expressed specifically in the shoot epidermis remain to be fully elucidated. We constructed double mutant combinations of these HD- ZIP IV mutant alleles and found that the double mutants of pdf2- 1 with homeodomain glabrous1- 1 ( hdg1- 1), hdg2- 3, hdg5- 1 and hdg12- 2 produced abnormal flowers with sepaloid petals and carpelloid stamens in association with the reduced expression of the petal and stamen identity gene APETALA 3 ( AP3). Expression of another petal and stamen identity gene PISTILATA ( PI) was less affected in these mutants. We confirmed that AP3 expression in pdf2- 1 hdg2- 3 was normally induced at the initial stages of flower development, but was attenuated both in the epidermis and internal cell layers of developing flowers. As the expression of PDF2 and these HD- ZIP IV genes during floral organ formation is exclusively limited to the epidermal cell layer, these double mutations may have non-cell-autonomous effects on AP3 expression in the internal cell layers. Our results suggest that cooperative functions of PDF2 and other members of the HD- ZIP IV family in the epidermis are crucial for normal development of floral organs in Arabidopsis. [ABSTRACT FROM AUTHOR]

AGL6-clade genes are a subfamily of MADS-box genes and preferentially expressed in floral organs. OsMADS6 and OsMADS17 are two AGL6-like genes in rice. OsMADS17 has been shown to play a minor role in floral development and appears to result from a duplication of OsMADS6. OsMADS6 was initially named as MFO1 for mosaic floral organs based on its moderate mutant phenotypes. So far, four moderate or weak mutant alleles of OsMADS6 have been described, providing valuable insights into its role in flower development. Here, we report a null allele of OsMADS6 ( Osmads6- 5), which exhibited a strong mutant phenotype in spikelet without affecting vegetative traits, causing all floral organs except lemma homeotically transformed into lemma-like organs (LLOs) as well as an indeterminate floral meristem, thus resulting in a mutant floret consisting of reiterating whorls of lemma and LLOs. In consistently, over-expression of OsMADS6 led to additional lodicule-, stamen- and carpel-like organs. Expression analysis showed that OsMADS6 controls the formation of the incipient primordia of lodicule, stamen and carpel via regulating the expression of class B, C and SEP-like MADS-box genes. Taken together, our results revealed that OsMADS6 acts as a critical regulator for early flower development in rice and provide novel insights into the molecular mechanism of OsMADS6. [ABSTRACT FROM AUTHOR]

The CUP-SHAPED COTYLEDON ( CUC)/ NO APICAL MERISTEM ( NAM) family of genes control boundary formation and lateral organ separation, which is critical for proper leaf and flower patterning. However, most downstream targets of CUC/NAM genes remain unclear., In a forward screen of the tobacco retrotransposon1 ( Tnt1) insertion population in Medicago truncatula, we isolated a weak allele of the no-apical-meristem mutant mtnam-2. Meanwhile, we regenerated a mature plant from the null allele mtnam-1. These materials allowed us to extensively characterize the function of MtNAM and its downstream genes., MtNAM is highly expressed in vegetative shoot buds and inflorescence apices, specifically at boundaries between the shoot apical meristem and leaf/flower primordia. Mature plants of the regenerated null allele and the weak allele display remarkable floral phenotypes: floral whorls and organ numbers are reduced and the floral organ identity is compromised. Microarray and quantitative RT-PCR analyses revealed that all classes of floral homeotic genes are down-regulated in mtnam mutants. Mutations in MtNAM also lead to fused cotyledons and leaflets of the compound leaf as well as a defective shoot apical meristem., Our results revealed that MtNAM shares the role of CUC/NAM family genes in lateral organ separation and compound leaf development, and is also required for floral organ identity and development. [ABSTRACT FROM AUTHOR]

How does evolution forge adaptive responses? Are many changes required or few? Just how complex are the transcriptional networks that control development? Diverse questions like these are being newly addressed by next-generation sequencing-based techniques. Facilitating a mechanistic understanding, these approaches reveal the direct in vivo interactions between transcription factors and their physical targets, combined with genome-scale readouts to comprehensively map adaptive gene regulatory networks (GRNs). Here l focus on pioneering work from the last 3 years that has leveraged these data to investigate diverse aspects of GRN circuitry controlling the reproductive transition in plants. These approaches have revealed surprising new functions for long-investigated key players in developmental programs and laid bare the basis for pleiotropy in many others, suggesting widespread process integration at the transcriptional level. Evolutionary questions begged by the recent deluge of GRN mapping data are being assessed anew, both by emerging work outside Arabidopsis thaliana and novel analyses within. These studies have swiftly exposed the distinctive power and adaptability of genome-wide GRN mapping and illustrate that this unique data type holds tremendous promise for plant biology. [ABSTRACT FROM AUTHOR]

Orchidaceae are an excellent model to examine perianth development because of their sophisticated floral architecture. In this study, we identified 24 APETALA3 (AP3)-like and 13 PISTILLA (PI)-like genes from 11 species of orchids and characterized them into four AP3- and two PI-duplicated homologs. The first duplication event in AP3 homologs occurring in the early evolutionary history of the Orchidaceae gave rise to AP3A and AP3B clades. Further duplication events resulted in four subclades, namely AP3A1, AP3A2, AP3B1 and AP3B2, during the evolution of Orchidaceae. The AP3 paralogous genes were expressed throughout inflorescence and floral bud development. From the in situ hybridization results, we noticed that the transition timings from ubiquitous to constrained expression in floral organs for both clades are different. The transition point of expression of the AP3A clade (clades 3 and 4) was at the late floral organ primordia stage. In contrast, that for the AP3B clade (clades 1 and 2) was not observed until the late inflorescence and floral bud stages. In addition, the AP3 orthologous genes revealed diverse expression patterns in various species of orchids, whereas the PI homologs were uniformly expressed in all floral whorls. AP3A2 orthologs play a noticeable role in lip formation because of their exclusive expression in the lip. Further evidence comes from the ectopic expression of AP3A2 detected in the lip-like petals extending from the lip in four sets of peloric mutants. Finally, a Homeotic Orchid Tepal (HOT) model is proposed, in which dualistic characters of duplicated B-class MADS-box genes are involved in orchid perianth development and growth. [ABSTRACT FROM PUBLISHER]

Wintersweet ( Chimonanthus praecox), a deciduous aromatic shrub endemic to China, has high ornamental value for developing beautiful flowers with strong fragrance. The transition from the vegetative to the reproductive phase in wintersweet takes 4-5 years. The molecular mechanism regulating flower development in this basal angiosperm is largely unknown. Here we characterized the molecular features and expression patterns of the C. praecox AGL6-like gene CpAGL6 and investigated its potential role in regulating floral time and organ development via ectopic expression in Arabidopsis thaliana. The expression of CpAGL6 is highly tissue-specific, with the highest level in the middle tepals, moderate levels in inner tepals and carpels, and weak levels in stamen and young leaf tissues. Its dynamic expression in the flower is coincident with tepal opening. Ectopic expression of CpAGL6 in Arabidopsis retarded the vegetative growth and led to precocious flowering, mainly correlated with the inhibition of the floral repressor FLC and promotion of the floral promoters AP1 and FT. Although no ectopic floral organs have been observed, transgenic plants exhibited abnormal stamen and carpel development in later-developing flowers, with fertility reduced to varying degrees. These results suggest that CpAGL6, the AGL6-like gene from the basal angiosperm C. praecox, is a potential E-function regulator involved in specifying floral time and organ identity, functionally homologous to those AGL6-like genes from higher eudicots and monocots. [ABSTRACT FROM AUTHOR]

Background and Aims The family of MADS box genes is involved in a number of processes besides controlling floral development. In addition to supplying homeotic functions defined by the ABC model, they influence flowering time and transformation of vegetative meristem into inflorescence meristem, and have functions in roots and leaves. Three Gerbera hybrida At-SOC1-like genes (Gh-SOC1–Gh-SOC3) were identified among gerbera expressed sequence tags. Methods Evolutionary relationships between SOC1-like genes from gerbera and other plants were studied by phylogenetic analysis. The function of the gerbera gene Gh-SOC1 in gerbera floral development was studied using expression analysis, protein–protein interaction assays and reverse genetics. Transgenic gerbera lines over-expressing or downregulated for Gh-SOC1 were obtained using Agrobacterium transformation and investigated for their floral phenotype. Key Results Phylogenetic analysis revealed that the closest paralogues of At-SOC1 are Gh-SOC2 and Gh-SOC3. Gh-SOC1 is a more distantly related paralogue, grouping together with a number of other At-SOC1 paralogues from arabidopsis and other plant species. Gh-SOC1 is inflorescence abundant and no expression was seen in vegetative parts of the plant. Ectopic expression of Gh-SOC1 did not promote flowering, but disturbed the development of floral organs. The epidermal cells of ray flower petals appeared shorter and their shape was altered. The colour of ray flower petals differed from that of the wild-type petals by being darker red on the adaxial side and greenish on the abaxial surface. Several protein–protein interactions with other gerbera MADS domain proteins were identified. Conclusions The At-SOC1 paralogue in gerbera shows a floral abundant expression pattern. A late petal expression might indicate a role in the final stages of flower development. Over-expression of Gh-SOC1 led to partial loss of floral identity, but did not affect flowering time. Lines where Gh-SOC1 was downregulated did not show a phenotype. Several gerbera MADS domain proteins interacted with Gh-SOC1. [ABSTRACT FROM AUTHOR]

Since the discovery of miRNAs in plants it has become clear that they are central to the regulation of many aspects of plant development and responses to the environment. miR172 regulates expression of a small group of AP2-like transcription factors in an evolutionarily ancient interaction. miR172 functions in regulating the transitions between developmental stages and in specifying floral organ identity. These two roles are conserved across monocotyledons and dicotyledons. Investigations into the roles of miR172 and its targets in phase changes in the model plant Arabidopsis have illustrated that this process is governed by complex regulatory systems. In addition to its conserved roles, miR172 has also acquired specialized species-specific functions in other aspects of plant development such as cleistogamy and tuberization. [ABSTRACT FROM PUBLISHER]

According to the modified ABC model, class B genes are expressed in whorl 1 as well as in whorls 2 and 3, therefore the organs of whorls 1 and 2 have the same petaloid structure in many monocots. The viridiflora tulip, a well-known cultivar group, has flowers in which the tepals in whorls 1 and 2 have greenish stripes. This phenotype could be expected as class B mutant by the modified ABC model. In this study, we discovered that tepal phenotypes correlated with that of stamens. We isolated two class A genes (TGSQA and TGSQB) from wild type tulip. Northern hybridization of these two class A genes, and the class B genes (TGDEFA, TGDEFB and TGGLO), showed that the expression of TGDEFA and TGDEFB in the viridiflora tulips were weaker than those in wild type cultivars, whereas the expression patterns of the rest genes were almost identical. From our results, we suggest that reduced expression of the two DEF-like genes, TGDEFA and TGDEFB, is involved in the development of the viridiflora phenotype. This reduced expression could be caused by the amino acid difference. [ABSTRACT FROM AUTHOR]

Abstract: One of the early successes of the application of molecular genetics to study plant development was the discovery of a series of genes that act together, in an apparently simple combinatorial model, to specify the identity of the different organs of a flower. Widely known as the ABC model, this framework for understanding has been investigated and modified over the course of the last two decades. The cast list of genes has been defined and, as other chapters in this volume will show, great progress has been made in understanding how they are regulated, how they act together, what they do and how they have contributed to the evolution of the flower in its varied forms. In this introductory review to the volume we will review the derivation and elaboration of the most current version of the ABC model, highlighting the modifications that have been necessary to ensure it fits the available experimental data. We will highlight the remaining difficulties in fitting the current model to the experimental data and propose a further modification to enable it to regain its applicability. [Copyright &y& Elsevier]