Reproductive Meristems Research Articles

Non-cell-autonomous signaling associated with barley ALOG1 specifies spikelet meristem determinacy

Inflorescence architecture and crop productivity are often tightly coupled in our major cereal crops. However, the underlying genetic mechanisms controlling cereal inflorescence development remain poorly understood. Here, we identified recessive alleles of barley (Hordeum vulgare L.) HvALOG1 (Arabidopsis thaliana LSH1 and Oryza G1) that produce non-canonical extra spikelets and fused glumes abaxially to the central spikelet from the upper-mid portion until the tip of the inflorescence. Notably, we found that HvALOG1 exhibits a boundary-specific expression pattern that specifically excludes reproductive meristems, implying the involvement of previously proposed localized signaling centers for branch regulation. Importantly, during early spikelet formation, non-cell-autonomous signals associated with HvALOG1 expression may specify spikelet meristem determinacy, while boundary formation of floret organs appears to be coordinated in a cell-autonomous manner. Moreover, barley ALOG family members synergistically modulate inflorescence morphology, with HvALOG1 predominantly governing meristem maintenance and floral organ development. We further propose that spatiotemporal redundancies of expressed HvALOG members specifically in the basal inflorescence may be accountable for proper patterning of spikelet formation in mutant plants. Our research offers new perspectives on regulatory signaling roles of ALOG transcription factors during the development of reproductive meristems in cereal inflorescences.

Genetic factors acting prior to dormancy in sour cherry influence bloom time the following spring.

Understanding the process of Prunus species floral development is crucial for developing strategies to manipulate bloom time and prevent crop loss due to climate change. Here, we present a detailed examination of flower development from initiation until bloom for early- and late-blooming sour cherries (Prunus cerasus) from a population segregating for a major bloom time QTL on chromosome 4. Using a new staging system, we show floral buds from early-blooming trees were persistently more advanced than those from late-blooming siblings. A genomic DNA coverage analysis revealed the late-blooming haplotype of this QTL, k, is located on a subgenome originating from the late-blooming P. fruticosa progenitor. Transcriptome analyses identified many genes within this QTL as differentially expressed between early- and late-blooming trees during the vegetative-to-floral transition. From these, we identified candidate genes for the late bloom phenotype, including multiple transcription factors homologous to Reproductive Meristem B3 domain-containing proteins. Additionally, we determined that the basis of k in sour cherry is likely separate from candidate genes found in sweet cherry-suggesting several major regulators of bloom time are located on Prunus chromosome 4.

Genetic control of thermomorphogenesis in tomato inflorescences

Understanding how plants alter their development and architecture in response to ambient temperature is crucial for breeding resilient crops. Here, we identify the quantitative trait locus qMULTIPLE INFLORESCENCE BRANCH 2 (qMIB2), which modulates inflorescence branching in response to high ambient temperature in tomato (Solanum lycopersicum). The non-functional mib2 allele may have been selected in large-fruited varieties to ensure larger and more uniform fruits under varying temperatures. MIB2 gene encodes a homolog of the Arabidopsis thaliana transcription factor SPATULA; its expression is induced in meristems at high temperature. MIB2 directly binds to the promoter of its downstream gene CONSTANS-Like1 (SlCOL1) by recognizing the conserved G-box motif to activate SlCOL1 expression in reproductive meristems. Overexpressing SlCOL1 rescue the reduced inflorescence branching of mib2, suggesting how the MIB2–SlCOL1 module helps tomato inflorescences adapt to high temperature. Our findings reveal the molecular mechanism underlying inflorescence thermomorphogenesis and provide a target for breeding climate-resilient crops.

Candidate gene analysis distinguishes regulatory mechanisms for phenological transitions in Indian and Snowball cauliflower

ABSTRACT The present study analysed expression of 13 candidate genes in relation to different developmental transitions (vegetative–curding–flowering) in Indian and snowball cauliflwer using quantitative real-time PCR (qRT-PCR). Expression levels of FRUITFULL-c (BoFUL-c), FLOWERING LOCUS T (BoFT), SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1), and LEAFY(BoFLY) increased from seedling to full curd stages in all varieties. VERNALIZATION2 (BoVRN2) and APETALA2 (BoAP2) genes showed a contrasting trend in Pusa Meghna (Indian type) and Pusa Snowball Kt-25 (Snowball type). High expression of BoVRN3, BoVIN2, and BoAP2 in Pusa Snowball Kt-25 fitted well with its vernalisation requirement. The increasing expression of BoFT, SOC1, and BoVIN3 while decreasing trend in BoLFY, REPRODUCTIVE MERISTEM (BoREM1), CAULIFLOWER (BoCAL), and BoFUL-d during seedling–curd initiation–full curd stages in Pusa Shukti (mid-late) matches with Pusa Snowball Kt-25, highlighting their genetic closeness. Hierarchical clustering of these 13 candidate genes grouped all the genes into two major clusters: one had the CAULIFLOWER CURD EXPRESSION 1 (CCE1), BoLFY, BoREM1, BoFUL-c, BoFUL-d, LEAFY Homologous (BoFH), and BoCAL genes while the rest of the genes constituted a second cluster. A significant interaction effect was observed in four candidate varieties and two growing situations (i.e. normal and lower temperature range) for curding-related phenological traits. The information will be helpful in understanding the curding behaviour.

TM3 and STM3 Promote Flowering Together with FUL2 and MBP20, but Act Antagonistically in Inflorescence Branching in Tomato.

The moment at which a plant transitions to reproductive development is paramount to its life cycle and is strictly controlled by many genes. The transcription factor SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) plays a central role in this process in Arabidopsis. However, the role of SOC1 in tomato (Solanum lycopersicum) has been sparsely studied. Here, we investigated the function of four tomato SOC1 homologs in the floral transition and inflorescence development. We thoroughly characterized the SOC1-like clade throughout the Solanaceae and selected four tomato homologs that are dynamically expressed upon the floral transition. We show that of these homologs, TOMATO MADS 3 (TM3) and SISTER OF TM3 (STM3) promote the primary and sympodial transition to flowering, while MADS-BOX PROTEIN 23 (MBP23) and MBP18 hardly contribute to flowering initiation in the indeterminate cultivar Moneyberg. Protein-protein interaction assays and whole-transcriptome analysis during reproductive meristem development revealed that TM3 and STM3 interact and share many targets with FRUITFULL (FUL) homologs, including cytokinin regulators. Furthermore, we observed that mutating TM3/STM3 affects inflorescence development, but counteracts the inflorescence-branching phenotype of ful2 mbp20. Collectively, this indicates that TM3/STM3 promote the floral transition together with FUL2/MBP20, while these transcription factors have opposite functions in inflorescence development.

ZmSPL13 and ZmSPL29 act together to promote vegetative and reproductive transition in maize.

Flowering time is a key agronomic trait determining environmental adaptation and yield potential of crops. The regulatory mechanisms of flowering in maize still remain rudimentary. In this study, we combine expressional, genetic, and molecular studies to identify two homologous SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors ZmSPL13 and ZmSPL29 as positive regulators of juvenile-to-adult vegetative transition and floral transition in maize. We show that both ZmSPL13 and ZmSPL29 are preferentially expressed in leaf phloem, vegetative and reproductive meristem. We show that vegetative phase change and flowering time are moderately delayed in the Zmspl13 and Zmspl29 single knockout mutants and more significantly delayed in the Zmspl13/29 double mutants. Consistently, the ZmSPL29 overexpression plants display precocious vegetative phase transition and floral transition, thus early flowering. We demonstrate that ZmSPL13 and ZmSPL29 directly upregulate the expression of ZmMIR172C and ZCN8 in the leaf, and of ZMM3 and ZMM4 in the shoot apical meristem, to induce juvenile-to-adult vegetative transition and floral transition. These findings establish a consecutive signaling cascade of the maize aging pathway by linking the miR156-SPL and the miR172-Gl15 regulatory modules and provide new targets for genetic improvement of flowering time in maize cultivars.

Assessing the role of REM13, REM34 and REM46 during the transition to the reproductive phase in Arabidopsis thaliana

REM (reproductive meristem) transcription factors have been proposed as regulators of plant reproductive development mainly based on their specific expression patterns in reproductive structures, but their roles are still largely unknown probably because of their redundancy. We selected three REM genes (REM13, REM34 and REM46) for functional analysis, based on their genome position and/or co-expression data.Our results suggest that these genes have a role in flowering time regulation and may modulate cell cycle progression. In addition, protein interaction experiments revealed that REM34 and REM46 interact with each other, suggesting that they might work cooperatively to regulate cell division during inflorescence meristem commitment.Previous attempts of using co-expression data as a guide for functional analysis of REMs were limited by the transcriptomic data available at the time. Our results uncover previously unknown functions of three members of the REM family of Arabidopsis thaliana and open the door to more comprehensive studies of the REM family, where the combination of co-expression analysis followed by functional studies might contribute to uncovering the biological roles of these proteins and the relationship among them.

The AtERF19 gene regulates meristem activity and flower organ size in plants.

Ethylene-responsive factors (ERFs) have diverse functions in the regulation of various plant developmental processes. Here, we demonstrate the dual role of an Arabidopsis ERF gene, AtERF19, in regulating reproductive meristem activity and flower organ size through the regulation of genes involved in CLAVATA-WUSCHEL (CLV-WUS) and auxin signaling, respectively. We found that AtERF19 stimulated the formation of flower primordia and controlled the number of flowers produced by activating WUS and was negatively regulated by CLV3. 35S::AtERF19 expression resulted in significantly more flowers, whereas 35S::AtERF19 + SRDX dominant-negative mutants produced fewer flowers. In addition, AtERF19 also functioned to control flower organ size by promoting the division/expansion of the cells through activating Small Auxin Up RNA Gene 32 (SAUR32), which positively regulated MYB21/24 in the auxin signaling pathway. 35S::AtERF19 and 35S::SAUR32 resulted in similarly larger flowers, whereas 35S::AtERF19 + SRDX and 35S::SAUR32-RNAi mutants produced smaller flowers than the wild type. The functions of AtERF19 were confirmed by the production of similarly more and larger flowers in 35S::AtERF19 transgenic tobacco (Nicotiana benthamiana) and in transgenic Arabidopsis which ectopically expressed the orchid gene (Nicotiana benthamiana) PaERF19 than in wild-type plants. The finding that AtERF19 regulates genes involved in both CLV-WUS and auxin signaling during flower development significantly expands the current knowledge of the multifunctional evolution of ERF genes in plants. The results presented in this work indicate a dual role for the transcription factor AtERF19 in controlling the number of flowers produced and flower organ size through the regulation of genes involved in CLV-WUS and auxin signaling, respectively. Our findings expand the knowledge of the roles of ERF genes in the regulation of reproductive development.

Flower-like meristem conditions and spatial constraints shape architecture of floral pseudanthia in Apioideae

BackgroundPseudanthia are multiflowered units that resemble single flowers, frequently by association with pseudocorollas formed by enlarged peripheral florets (ray flowers). Such resemblance is not only superficial, because numerous pseudanthia originate from peculiar reproductive meristems with flower-like characteristics, i.e. floral unit meristems (FUMs). Complex FUM-derived pseudanthia with ray flowers are especially common in Apiaceae, but our knowledge about their patterning is limited. In this paper, we aimed to investigate both the genetic and morphological basis of their development.ResultsWe analysed umbel morphogenesis with SEM in six species representing four clades of Apiaceae subfamily Apioideae with independently acquired floral pseudanthia. Additionally, using in situ hybridization, we investigated expression patterns of LEAFY (LFY), UNUSUAL FLORAL ORGANS (UFO), and CYCLOIDEA (CYC) during umbel development in carrot (Daucus carota subsp. carota). Here, we show that initial differences in size and shape of umbel meristems influence the position of ray flower formation, whereas an interplay between peripheral promotion and spatial constraints in umbellet meristems take part in the establishment of specific patterns of zygomorphy in ray flowers of Apiaceae. This space-dependent patterning results from flower-like morphogenetic traits of the umbel which are also visible at the molecular level. Transcripts of DcLFY are uniformly distributed in the incipient umbel, umbellet and flower meristems, while DcCYC shows divergent expression in central and peripheral florets.ConclusionsOur results indicate that umbels develop from determinate reproductive meristems with flower-like characteristics, which supports their recognition as floral units. The great architectural diversity and complexity of pseudanthia in Apiaceae can be explained by the unique conditions of FUMs—an interplay between expression of regulatory genes, specific spatio-temporal ontogenetic constraints and morphogenetic gradients arising during expansion and repetitive fractionation. Alongside Asteraceae, umbellifers constitute an interesting model for investigation of patterning in complex pseudanthia.

Cone-setting in spruce is regulated by conserved elements of the age-dependent flowering pathway.

Reproductive phase change is well characterized in angiosperm model species, but less studied in gymnosperms. We utilize the early cone-setting acrocona mutant to study reproductive phase change in the conifer Picea abies (Norway spruce), a gymnosperm. The acrocona mutant frequently initiates cone-like structures, called transition shoots, in positions where wild-type P. abies always produces vegetative shoots. We collect acrocona and wild-type samples, and RNA-sequence their messenger RNA (mRNA) and microRNA (miRNA) fractions. We establish gene expression patterns and then use allele-specific transcript assembly to identify mutations in acrocona. We genotype a segregating population of inbred acrocona trees. A member of the SQUAMOSA BINDING PROTEIN-LIKE (SPL) gene family, PaSPL1, is active in reproductive meristems, whereas two putative negative regulators of PaSPL1, miRNA156 and the conifer specific miRNA529, are upregulated in vegetative and transition shoot meristems. We identify a mutation in a putative miRNA156/529 binding site of the acrocona PaSPL1 allele and show that the mutation renders the acrocona allele tolerant to these miRNAs. We show co-segregation between the early cone-setting phenotype and trees homozygous for the acrocona mutation. In conclusion, we demonstrate evolutionary conservation of the age-dependent flowering pathway and involvement of this pathway in regulating reproductive phase change in the conifer P. abies.

FaLEC2 repressing FaLOX2 promoter involved in the metabolism of LOX-derived volatiles during strawberry ripening

• FaLOX2 expression level was negatively correlated with hexanal content. • RNA-Seq identified 43 B3 TFs, including LAV (3), RAV (18), ARF (13), and REM (9). • FaLEC2 expression level was negatively correlated with ( E,Z )-2,6-nonadienal content. • FaLEC2 transcriptionally repressed the activity of FaLOX2 promoter. Lipoxygenase (LOX) pathway is the key and the most important pathway for the metabolism of fruit volatile. However, the transcription mechanism of the LOX pathway is still obscure in non-climacteric fruit. In order to identify the transcription factor involved in LOX-derived volatile metabolism, RNA sequencing and metabolome were used to profile strawberry ( Fragaria × ananassa Duch.). Correlation analysis shows that the expression of FaLOX2 was negatively correlated with the hexanal content ( r = −0.985). The RY element that specifically bound by the B3 domain transcription factors, are found in FaLOX2 promoter. B3 domain-containing transcription factors including LEAFY COTYLEDON2 (LEC2)–ABI3–VAL (LAV, 3), RELATED TO ABI3 and VP1 (RAV, 18), AUXIN RESPONSE FACTOR (ARF, 13), and REPRODUCTIVE MERISTEM (REM, 9) are identified. It is noticed that FaLEC2 expression is negatively correlated with ( E,Z )-2,6-nonadienal content ( r = −1.000). Yeast one-hybrid analysis and dual-luciferase analysis suggest that FaLEC2 transcriptionally represses the activity of FaLOX2 promoter. Moreover, FaLEC2 expression level is negatively correlated with FaLOX2 expression ( r = −0.956). Here, our demonstration that FaLEC2 trans-represses the activity of the FaLOX2 promoter provides evidence that FaLEC2 directly controls a transcriptional program for LOX-derived volatile metabolism in strawberries.

Modeling phyllotaxis: From the inhibition potential to the real plant

We developed a new parametrization of the classic Douady and Couder model of phyllotaxis based on the inhibition potential: it allowed us to accurately reproduce the vegetative meristem of Linum usitatissimum displaying Fibonacci phyllotaxis, and the reproductive meristem of Ranunculus repens. We calculated the inhibition potential within the meristem and the auxin concentration at the front. We show that phyllotaxis modes and the convergence of the divergence angles towards “noble” angles are the consequence of minimizing the inhibitory potential under the constraint of decreasing plastochron ratios. Our approach, which gives a physicochemical basis to the van Iterson diagram, produces the same results as approaches based on mechanical constraints, suggesting these are two facets of the same botanical reality.

Advances in Citrus Flowering: A Review.

Citrus are polycarpic and evergreen species that flower once in spring or several times a year depending on the genotype and the climatic conditions. Floral induction is triggered by low temperature and water-deficit stress and occurs 2–3 months before bud sprouting, whereas differentiation takes place at the same time as sprouting. The induced buds develop single flowers or determinate inflorescences, so that vegetative growth is required at the axillary buds to renew the polycarpic habit. The presence of fruits inhibits sprouting and flower induction from nearby axillary buds in the current season. In some species and cultivars, this results in low flowering intensity the following spring, thus giving rise to alternate bearing. A number of key flowering genes act in the leaf (CiFT3, CcMADS19, etc.) or in the bud (CsLFY, CsTFL1, etc.) to promote or inhibit both flowering time and reproductive meristem identity in response to these climatic factors, the fruit dominance, or the age of the plant (juvenility). The expression of some of these genes can be modified by gibberellin treatments, which reduce bud sprouting and flowering in adult trees, and constitute the main horticultural technique to control flowering in citrus. This review presents a comprehensive view of all aspects of the flowering process in citrus, converging the research published during the past half century, which focused on plant growth regulators and the nutritional source-sink relationships and guided research toward the study of gene transcription and plant transformation, and the advances made with the development of the tools of molecular biology published during the current century.

Untangling inflorescences in Miconieae (Melastomataceae): development, typology, and the systematic and evolutionary implications.

This study aimed to describe the origin, position, development and typology of inflorescences in Miconieae through ontogenetic and morphological analyses using light microscopy. We observed three morphological character states: terminal, pseudo-axillary and axillary; and two ontogenetic states: terminal and axillary. The terminal and pseudoaxillary inflorescences originate from terminal reproductive meristems. Pseudoaxillary inflorescences result from unequal development of vegetative meristems which flank the terminal flowering unit, whereas in terminal inflorescences, both vegetative meristems develop equally. In axillary inflorescences, the terminal reproductive meristem is not involved, while axillary inflorescences originate from reproductive axillary meristems. The inflorescences range from heterocladic and thyrsoid to simpler types, such as botryoid and triad. Such characteristics can also be seen in paracladia, particularly those most distal. The terminal inflorescence is observed in all clades of Miconieae, and pseudoaxillary and axillary inflorescences should be apomorphic states in the tribe and derived from the terminal condition.

A cellular analysis of meristem activity at the end of flowering points to cytokinin as a major regulator of proliferative arrest in Arabidopsis

In monocarpic plants, all reproductive meristem activity arrests and flower production ceases after the production of a certain number of fruits. This proliferative arrest (PA) is an evolutionary adaptation that ensures nutrient availability for seed production. Moreover, PA is a process of agronomic interest because it affects the duration of the flowering period and therefore fruit production. While our knowledge of the inputs and genetic factors controlling the initiation of the flowering period is extensive, little is known about the regulatory pathways and cellular events that participate in the end of flowering and trigger PA. Here, we characterize with high spatiotemporal resolution the cellular and molecular changes related to cell proliferation and meristem activity in the shoot apical meristem throughout the flowering period and PA. Our results suggest that cytokinin (CK) signaling repression precedes PA and that this hormone is sufficient to prevent and revert the process. We have also observed that repression of known CK downstream factors, such as type B cyclins and WUSCHEL (WUS), correlates with PA. These molecular changes are accompanied by changes in cell size and number likely caused by the cessation of cell division and WUS activity during PA. Parallel assays in fruitfull (ful) mutants, which do not undergo PA, have revealed that FUL may promote PA via repression of these CK-dependent pathways. Moreover, our data allow to define two phases, based on the relative contribution of FUL, that lead to PA: an early reduction of CK-related events and a late blocking of these events.

Chilling-Requirement Release of Seed and Bud Dormancy in Apricot

Dormancy shows common physiological features in buds and seeds. Specific period of chilling is usually required to release dormancy. Reproductive meristems and embryos display dormancy mechanisms in specialized structures named respectively buds and seeds that arrest the growth of perennial plants until environmental conditions are optimal for survival. Chilling requirements for breaking dormancy were studied for 3 successive years in 20 seedling apricot trees which spanned the range of flowering times in these trees. Different methods for estimating chilling requirements were evaluated and compared, and correlations between chilling requirements and flowering date were established. The trees examined showed a range of chilling requirements, chill hours (CH) between 199 CH and 274 CH, and chill units, (CU), between 612CU and 873CU. The results obtained in different years by the Utah and Dynamic models were more homogeneous with respect to the hours below 7 °C model. The apricot trees showed important differences concerning flowering date, and the results indicate a high positive correlation between chilling requirements and flowering date.Moreover, a specific low-temperature stratification treatment was required to overcome seed dormancy. 5°C cold stratification was found to be the best for breaking seed dormancy and germination. Increased seed germination percentage was recorded when the period of stratification prolonged. Apricot seeds required a cold stratification of about 12-15 days to reach maximum germination.

Agronomic performance and flowering behavior in response to photoperiod and vernalization in barley (Hordeum vulgare L.) Genotypes with contrasting drought tolerance behavior

In dry environments, the appropriate matching of reproductive development with water availability is considered very crucial for crop success. In this study, the role of variations in flowering and drought tolerance in selected barley genotypes with contrasting drought tolerance behavior was studied under field and controlled conditions. For this purpose, field trials were conducted for two consecutive seasons at three diverse locations where the studied genotypes were subjected to either rainfed conditions or rainfed plus supplementary irrigation under two different sowing dates. Furthermore, reproductive meristem development was assessed in two selected barley genotypes, Rum (drought tolerant) and Steptoe (drought-sensitive), in response to both vernalization and water stress under two different photoperiod conditions. Variation in the number of days to heading was more pronounced under rainfed conditions than under rainfed plus supplementary irrigated conditions. For agronomic performance, Rum was superior under all tested environments, which assures its general adaptability to dry environments. In addition, Rum was found to be the most stable genotype under dry conditions. Based on sowing and water regime treatments, a signifcant negative correlation was detected between heading date and yield was detected in field grown Rum and Steptoe. Under controlled conditions, the transition to reproductive meristem was faster under vernalized long-day conditions compared to vernalized short-day conditions. The progress of shoot apical meristem development and heading under long-day conditions was significantly faster in Rum compared to Steptoe. A pronounced effect of drought stress was observed on shoot apical meristem development in Steptoe. Under short-day conditions, vernalized Rum plants subjected to drought showed an advanced meristem development stage and a significantly earlier heading compared to non-stressed plants. This early heading in stressed Rum plants under short-day conditions was accompanied by higher gene expression of the Vrn-H1 and Vrn-H3 genes. In conclusion, the integration of vernalization and photoperiod signals in drought-tolerant barley genotypes was associated with early heading and higher productivity in dry environments.

Genome-wide analysis reveals widespread roles for RcREM genes in floral organ development in Rosa chinensis

Members of the REM (Reproductive Meristem) gene family are expressed primarily in reproductive meristems and floral organs. However, their evolution and their functional profiles in flower development remain poorly understood. Here, we performed genome-wide identification and evolutionary analysis of the REM gene family in Rosaceae. This family has been greatly expanded in rose (Rosa chinensis) compared to other species, primarily through tandem duplication. Expression analysis revealed that most RcREM genes are specifically expressed in reproductive organs and that their specific expression patterns are dramatically altered in rose plants with mutations affecting floral organs. Protein-protein interaction analysis indicated that RcREM14 interact with RcAP1 (one of the homology of A class genes in ABCDE model), highlighting the roles of RcREM genes in floral organ identity. Finally, co-expression network analysis indicated that RcREM genes are co-expressed with a high proportion of key genes that regulate flowering time, floral organ development, and cell proliferation and expansion in R. chinensis.

Analysis of the structure and function of the tomato Solanum lycopersicum L. MADS-box gene SlMADS5.

At all stages of f lowering, a decisive role is played by the family of MADS-domain transcription factors, the combinatorial action of which is described by the ABCDE-model of f lower development. The current volume of data suggests a high conservatism of ABCDE genes in angiosperms. The E-proteins SEPALLATA are the central hub of the MADS-complexes, which determine the identity of the f loral organs. The only representative of the SEPALLATA3 clade in tomato Solanum lycopersicum L., SlMADS5, is involved in determining the identity of petals, stamens, and carpels; however, data on the functions of the gene are limited. The study was focused on the SlMADS5 functional characterization. Structural and phylogenetic analyses of SlMADS5 conf irmed its belonging to the SEP3 clade. An in silico expression analysis revealed the absence of gene transcripts in roots, leaves, and shoot apical meristem, and their presence in f lowers, fruits, and seeds at different stages of development. Two-hybrid analysis showed the ability of SlMADS5 to activate transcription of the target gene and interact with TAGL1. Transgenic plants Nicotiana tabacum L. with constitutive overexpression of SlMADS5 cDNA f lowered 2.2 times later than the control; plants formed thickened leaves, 2.5–3.0 times thicker stems, 1.5–2.7 times shortened internodes, and 1.9 times fewer f lowers and capsules than non-transgenic plants. The f lower structure did not differ from the control; however, the corolla petals changed color from light pink to magenta. Analysis of the expression of SlMADS5 and the tobacco genes NtLFY, NtAP1, NtWUS, NtAG, NtPLE, NtSEP1, NtSEP2, and NtSEP3 in leaves and apexes of transgenic and control plants showed that SlMADS5 mRNA is present only in tissues of transgenic lines. The other genes analyzed were highly expressed in the reproductive meristem of control plants. Gene transcripts were absent or were imperceptibly present in the leaves and vegetative apex of the control, as well as in the leaves and apexes of transgenic lines. The results obtained indicate the possible involvement of SlMADS5 in the regulation of f lower meristem development and the pathway of anthocyanin biosynthesis in petals.

Біоморфологічний аналіз культивованої флори плоских зелених дахів міста Львова

Досліджено біоморфологічні характеристики культивованих видів рослин, ідентифікованих на 24 озеленених плоских дахах екстенсивного типу у Львові. Встановлено, що для створення рослинних композицій використано 225 видів, 136 культиварів, 14 гібридів із 55 родин та 143 родів. Здійснено біоморфологічний аналіз культивованої флори, складеної із 326 видів, гібридів та культиварів, які успішно акліматизувалися на дахах і ростуть на них більше двох років. Проаналізовано спектри життєвих форм, виділених на основі різних класифікаційних систем із застосуванням різних морфологічних критеріїв. Встановлено взаємозв'язок між життєвістю рослини і її біоморфологічними характеристиками та зроблено висновки про доцільність використання певних біоморф для озеленення покрівель. За класифікацією життєвих форм І. Серебрякова (1962), основним критерієм для виділення життєвих форм вважають довговічність скелетних осей, що є проявом адаптивної реакції рослини на умови середовища. Наші дослідження підтвердили успішність адаптації на дахах багаторічних рослин із здерев'янілими чи підземними метаморфізованими органами, серед них кущі (116 видів; 35,6 %), полікарпічні трави (107; 32,9 %) та дерева (43; 13,2 %). За системою С. Raunkiaer (1934), основою для виділення клімаморф є захист бруньок поновлення та апікальних меристем пагона. За нашими спостереженнями, на дахах більше двох років витримують рослини із добре захищеними бруньками – це 102 види листопадних і 65 вічнозелених фанерофітів (51,2 % від загальної кількості), гемікриптофіти (27,6 %) із захищеною опадом рослини і снігом верхівковою брунькою та криптофіти-геофіти (14,2 %) із схованими глибоко під землею бруньками. Згідно зі системою R. Whittaker (1970) біоморфи рослин є результатом ценотичної взаємодії видів в екосистемах, а умови середовища визначають тип надземних органів рослин, що підтверджено і нашими дослідженнями. Кожен із органів рослин, а також всі окремі ознаки біоморф перебувають у тісному взаємозв'язку із умовами середовища, а тому на дахах найкраще виживають широколисті листопадні дерева (24; 7,4 %), широколисті листопадні кущі (71; 21,8 %), та різнотрав'я (72; 22,3 %). За лінійною системою життєвих форм В. М. Голубєва (1972), біоморфологічні ознаки рослин можна оцінити незалежно одна від одної без виділення життєвих форм, проте кожна окремо взята ознака відображає тип пристосування рослини до умов середовища. Встановлено, що для зелених дахів найбільш характерні кущі (116; 35,6 %), літньозеленого типу (220; 67,5 %), безрозеткові (324; 99,4 %), із змішаною кореневою системою (219; 67,2 %), без виражених підземних кореневищних структур (265; 81,3 %). Встановлено, що на дахах висотних будівель найкращу життєвість мають низькорослі листопадні кущі та сукуленти. Вище 20 м для здешевлення догляду саду взимку варто ширше застосовувати однорічні рослини. Натомість на дахах недоцільно використовувати такі біоморфи як цибулинні ефемероїди, стрижнекореневі рослини, види із здерев'янілими кореневищами, а також вічнозелені широколистяні види та хвойні з ламкими гілками.