Comprehensive Analysis of the NF-YB Gene Family and Expression under Abiotic Stress and Hormone Treatment in Larix kaempferi.

NF-YB, a subfamily of Nuclear Factor Y (NF-Y) transcription factor, play crucial role in many biological processes of plant growth and development and abiotic stress responses, and they can therefore be good candidate factors for breeding stress-resistant plants. However, the NF-YB proteins have not yet been explored in Larix kaempferi, a tree species with high economic and ecological values in northeast China and other regions, limiting the breeding of anti-stress L. kaempferi. In order to explore the roles of NF-YB transcription factors in L. kaempferi, we identified 20 LkNF-YB family genes from L. kaempferi full-length transcriptome data and carried out preliminary characterization of them through series of analyses on their phylogenetic relationships, conserved motif structure, subcellular localization prediction, GO annotation, promoter cis-acting elements as well as expression profiles under treatment of phytohormones (ABA, SA, MeJA) and abiotic stresses (salt and drought). The LkNF-YB genes were classified into three clades through phylogenetic analysis and belong to non-LEC1 type NF-YB transcription factors. They have 10 conserved motifs; all genes contain a common motif, and their promoters have various phytohormones and abiotic stress related cis-acting elements. Quantitative real time reverse transcription PCR (RT-qPCR) analysis showed that the sensitivity of the LkNF-YB genes to drought and salt stresses was higher in leaves than roots. The sensitivity of LKNF-YB genes to ABA, MeJA, SA stresses was much lower than that to abiotic stress. Among the LkNF-YBs, LkNF-YB3 showed the strongest responses to drought and ABA treatments. Further protein interaction prediction analysis for LkNF-YB3 revealed that LkNF-YB3 interacts with various factors associated with stress responses and epigenetic regulation as well as NF-YA/NF-YC factors. Taken together, these results unveiled novel L. kaempferi NF-YB family genes and their characteristics, providing the basic knowledge for further in-depth studies on their roles in abiotic stress responses of L. kaempferi.

Five NUCLEAR FACTOR-Y subunit B genes in rapeseed (Brassica napus) promote flowering and root elongation in Arabidopsis.

MAIN CONCLUSION: Heterologous expression of BnNF-YB2, BnNF-YB3, BnNF-YB4, BnNF-YB5, or BnNF-YB6 from rapeseed promotes the floral process and also affects root development in Arabidopsis. The transcriptional regulator NUCLEAR FACTOR-Y (NF-Y) is a heterotrimeric complex composed of NF-YA, NF-YB, and NF-YC proteins and is ubiquitous in yeast, animal, and plant systems. In this study, we found that five NF-YB proteins from rapeseed (Brassica napus), including BnNF-YB2, BnNF-YB3, BnNF-YB4, BnNF-YB5, and BnNF-YB6 (BnNF-YB2/3/4/5/6), all function in photoperiodic flowering and root elongation. Sequence alignment and phylogenetic analysis showed that BnNF-YB2/3 and BnNF-YB4/5/6 were clustered with Arabidopsis AtNF-YB2 and AtNF-YB3, respectively, implying that these NF-YBs are evolutionarily and functionally conserved. In support of this hypothesis, the heterologous expression of individual BnNF-YB2, 3, 4, 5, or 6 in Arabidopsis promoted early flowering under a long-day photoperiod. Further analysis suggested that BnNF-YB 2/3/4/5/6 elevated the expression of key downstream flowering time genes including CO, FT, LFY and SOC1. Promoter-GUS fusion analysis showed that the five BnNF-YBs were expressed in a variety of tissues at various developmental stages and GFP fusion analysis revealed that all BnNF-YBs were localized to the nucleus. In addition, we demonstrated that the heterologous expression of individual BnNF-YB2/3/4/5/6 in Arabidopsis promoted root elongation and increased the number of root tips formed under both normal and treatment with simulators of abiotic stress conditions.

OsMADS14 and NF-YB1 cooperate in the direct activation of OsAGPL2 and Waxy during starch synthesis in rice endosperm.

Starch synthesis makes a dramatic contribution to the yield and nutritional value of cereal crops. Although several starch synthesis enzymes and related regulators have been reported, the underlying regulatory mechanisms of starch synthesis remain largely unknown. OsMADS14 is a FRUITFULL (FUL)-like MADS-box gene in rice (Oryza sativa). Here we show that two null mutations of OsMADS14 result in a shrunken and chalky grain phenotype. It is caused by obviously defective compound starch granules and a significantly reduced content of both total starch and amylose in the endosperm. Transcriptomic profiling analyses revealed that the loss-of-function of OsMADS14 leads to significantly downregulated expression of many core starch synthesis genes, including OsAGPL2 and Waxy. Both in vitro and in vivo assays demonstrate that the OsMADS14 protein directly binds to stretches of DNA with a CArG-box consensus in the putative regulatory regions of OsAGPL2 and Waxy. Protein-protein interaction experiments also suggest that OsMADS14 interacts with nuclear factor NF-YB1 to promote the transcription of OsAGPL2 and Waxy. Our study thus demonstrates that OsMADS14 plays an essential role in the synthesis of storage starch and provides novel insights into the underlying molecular mechanism that may be used to improve rice cultivars by molecular breeding.

Identification and Characterization of Abiotic Stress-Responsive NF-YB Family Genes in Medicago.

Nuclear factor YB (NF-YB) are plant-specific transcription factors that play a critical regulatory role in plant growth and development as well as in plant resistance against various stresses. In this study, a total of 49 NF-YB genes were identified from the genomes of Medicago truncatula and Medicago sativa. Multiple sequence alignment analysis showed that all of these NF-YB members contain DNA binding domain, NF-YA interaction domain and NF-YC interaction domain. Phylogenetic analysis suggested that these NF-YB proteins could be classified into five distinct clusters. We also analyzed the exon-intron organizations and conserved motifs of these NF-YB genes and their deduced proteins. We also found many stress-related cis-acting elements in their promoter region. In addition, analyses on genechip for M. truncatula and transcriptome data for M. sativa indicated that these NF-YB genes exhibited a distinct expression pattern in various tissues; many of these could be induced by drought and/or salt treatments. In particular, RT-qPCR analysis revealed that the expression levels of gene pairs MsNF-YB27/MtNF-YB15 and MsNF-YB28/MtNF-YB16 were significantly up-regulated under NaCl and mannitol treatments, indicating that they are most likely involved in salt and drought stress response. Taken together, our study on NF-YB family genes in Medicago is valuable for their functional characterization, as well as for the application of NF-YB genes in genetic breeding for high-yield and high-resistance alfalfa.

CmNF-YB8 affects drought resistance in chrysanthemum by altering stomatal status and leaf cuticle thickness.

Drought is a major abiotic stress that limits plant growth and development. Adaptive mechanisms have evolved to mitigate drought stress, including the capacity to adjust water loss rate and to modify the morphology and structure of the epidermis. Here, we show that the expression of CmNF-YB8, encoding a nuclear factor Y (NF-Y) B-type subunit, is lower under drought conditions in chrysanthemum (Chrysanthemum morifolium). Transgenic chrysanthemum lines in which transcript levels of CmNF-YB8 were reduced by RNA interference (CmNF-YB8-RNAi) exhibited enhanced drought resistance relative to control lines, whereas lines overexpressing CmNF-YB8 (CmNF-YB8-OX) were less tolerant to drought. Compared to wild type (WT), CmNF-YB8-RNAi plants showed reduced stomatal opening and a thicker epidermal cuticle that correlated with their water loss rate. We also identified genes involved in stomatal adjustment (CBL-interacting protein kinase 6, CmCIPK6) and cuticle biosynthesis (CmSHN3) that are more highly expressed in CmNF-YB8-RNAi lines than in WT, CmCIPK6 being a direct downstream target of CmNF-YB8. Virus-induced gene silencing of CmCIPK6 or CmSHN3 in the CmNF-YB8-RNAi background abolished the effects of CmNF-YB8-RNAi on stomatal closure and cuticle deposition, respectively. CmNF-YB8 thus regulates CmCIPK6 and CmSHN3 expression to alter stomatal movement and cuticle thickness in the leaf epidermis, thereby affecting drought resistance.

The soybean GmNFY-B1 transcription factor positively regulates flowering in transgenic Arabidopsis.

Nuclear Factor Y (NF-Y) gene family regulates numbers of flowering processes. Two independent transgenic Arabidopsis lines overexpressing (OX) GmNFY-B1 and GmNFYB1-GR (GmNFYB1 fused with the glucocorticoid receptor) were used to investigate the function of NFY-B1 in flowering. Furthermore, GmNFYB1-GR lines were chemically treated with dexamethasone (Dex, synthetic steroid hormone), cycloheximide (Cyc, an inhibitor of protein biosynthesis), and ethanol to examine their effects on different flowering related marker genes. Our results indicated that the transgenic lines produced longer hypocotyl lengths and had fewer numbers of rosette leaves compared to the wild-type and nf-yb1 mutant plants under both long and short-day (LD and SD) conditions. The qRT-PCR assays revealed that transcript levels of all flowering time regulating genes, i.e. SOC, FLC, FT, TSF, LFY, GI2, AGL, and FCA showed higher transcript abundance in lines OX GmNFYB1-GR. However, FT and GI genes showed higher transcript levels under Dex and Dex/Cyc treatments compared to Cyc and ethanol. Additionally, 24 differentially expressed genes were identified and verified through RNA-seq and RT-qPCR in GmNF-YB1-GR lines under Cyc and Dex/Cyc treatments from which 14 genes were up-regulated and 10 were down-regulated. These genes are involved in regulatory functions of circadian rhythm, regulation of flower development in photoperiodic, and GA pathways. The overexpression of GmNF-YB1 and GmNF-YB1-GR promote flowering through the higher expression of flowering-related genes. Further GmNF-YB1 and its attachment with the GR receptor can regulate its target genes under Dex/Cyc treatment and might act as flowering inducer under LD and SD conditions.

NF-Y-dependent regulation of glutamate receptor 4 expression and cell survival in cells of the oligodendrocyte lineage.

Glutamate receptor subunit 4 (GluA4) is highly expressed by neural cells sensitive to excitotoxicity, and is the predominant subunit expressed by oligodendrocyte precursor cells (OPC) during a key period of vulnerability to hypoxic-ischemic injury. Therefore, transcriptional networks downstream of excitotoxic GluA4 activation represent a promising area for therapeutic intervention. In this work, we identify the CCAAT binding transcription factor NF-Yb as a novel transcriptional regulator of Gria4 (GluA4 gene), and a controller of excitotoxic death in the oligodendroglial lineage. We describe a novel regulatory region within Gria4 containing CCAAT sequences whose binding by NF-Yb is regulated by excitotoxicity. Excitotoxicity-induced alterations in NF-Yb binding are associated with changes in Gria4 transcription, while knockdown of NF-Yb alters the transcription of reporter constructs containing this regulatory region. Data from immortalized and primary OPC reveal that RNAi and pharmacological disruption of NF-Yb alter Gria4 transcription, with the latter inducing apoptosis and influencing a set of apoptotic genes similarly regulated during excitotoxicity. These data provide the first definition of a trans-acting mechanism regulating Gria4, and identify the NF-Y network as a potential source of pharmacological targets for promoting OPC survival.

Genome-Wide Analysis of the NF-YB Gene Family in Gossypium hirsutum L. and Characterization of the Role of GhDNF-YB22 in Embryogenesis.

Members of the NF-YB transcription factor gene family play important roles in diverse processes related to plant growth and development, such as seed development, drought tolerance, and flowering time. However, the function of NF-YB genes in cotton remains unclear. A total of 23, 24, and 50 NF-YB genes were identified in Gossypium arboreum (G. arboreum), Gossypium raimondii (G. raimondii), and G. hirsutum, respectively. A systematic phylogenetic analysis was carried out in G. arboretum, G. raimondii, G. hirsutum, Arabidopsis thaliana, cacao, rice and, sorghum, where the 150 NF-YB genes were divided into five groups (α-ε). Of these groups, α is the largest clade, and γ contains the LEC1 type NF-YB proteins. Syntenic analyses revealed that paralogues of NF-YB genes in G. hirsutum exhibited good collinearity. Owing to segmental duplication within the A sub-genome (At) and D sub-genome (Dt), there was an expanded set of NF-YB genes in G. hirsutum. Furthermore, we investigated the structures of exons, introns, and conserved motifs of NF-YB genes in upland cotton. Most of the NF-YB genes had only one exon, and the genes from the same clade exhibited a similar motif pattern. Expression data show that most NF-YB genes were expressed ubiquitously, and only a few genes were highly expressed in specific tissues, as confirmed by quantitative real-time PCR (qRT-PCR) analysis. The overexpression of GhDNF-YB22 gene, predominantly expressed in embryonic tissues, indicates that GhDNF-YB22 may affect embryogenesis in cotton. This study is the first comprehensive characterization of the GhNF-YB gene family in cotton, and showed that NF-YB genes could be divided into five clades. The duplication events that occurred over the course of evolution were the major impetus for NF-YB gene expansion in upland cotton. Collectively, this work provides insight into the evolution of NF-YB in cotton and further our knowledge of this commercially important species.

Targeted gene disruption coupled with metabolic screen approach to uncover the LEAFY COTYLEDON1-LIKE4 (L1L4) function in tomato fruit metabolism.

KEY MESSAGE: Functional analysis of tomato L1L4 master transcription factor resulted in important metabolic changes affecting tomato fruit quality. Tomato fruits from mutant lines bearing targeted disruption of the heterotrimeric nuclear transcription factor Y (NF-Y) transcription factor (TF) gene LEAFY-COTYLEDON1-LIKE4 (L1L4, NF-YB6), a master regulator of biosynthesis for seed storage proteins and fatty acids, were evaluated for metabolites content and morphology. Metabolic screens using LC-MS/MS-based analysis and physico-chemical methods in different L1L4 mutants of the fourth generation allowed a comparative assessment of the effects of the TF disruption. Mutagenesis resulted in fruits phenotypically similar to wild-type with subtle shape differences in the distal end protrusion and symmetry. Conversely, mutant fruits from independent lines had significant variation in moisture content, titratable acidity and overall metabolite profiles including oxalic and citric acid, fructose, ß-carotene, total polyphenols and antioxidants. Lines 6, 7 and 9 were the richest in ß-carotene and antioxidant activity, line 4 in ascorbic acid and lines 4 and 8 in succinic acid. The reduced content of the anti-nutrient oxalic acid in several mutant fruits suggests that L1L4 gene may regulate the accumulation of this compound during fruit development. Detailed LC-MS/MS analysis of mutant seeds showed substantial differences in bioactive compounds compared to wild-type seeds. Taken together, the results suggest that the L1L4 TF is a significant regulator of metabolites both in tomato fruit and seeds providing a molecular target for crop improvement. Elucidation of the candidate genes encoding key enzymes in the affected metabolic pathways aimed to facilitate the L1L4 gene network exploration and eventually lead to systems biology approaches in tomato fruit quality.

Identification and characterization of NF-YB family genes in tung tree.

The NF-YB transcription factor gene family encodes a subunit of the CCAAT box-binding factor (CBF), a highly conserved trimeric activator that strongly binds to the CCAAT box promoter element. Studies on model plants have shown that NF-YB proteins participate in important developmental and physiological processes, but little is known about NF-YB proteins in trees. Here, we identified seven NF-YB transcription factor-encoding genes in Vernicia fordii, an important oilseed tree in China. A phylogenetic analysis separated the genes into two groups; non-LEC1 type (VfNF-YB1, 5, 7, 9, 11, 13) and LEC1-type (VfNF-YB 14). A gene structure analysis showed that VfNF-YB 5 has three introns and the other genes have no introns. The seven VfNF-YB sequences contain highly conserved domains, a disordered region at the N terminus, and two long helix structures at the C terminus. Phylogenetic analyses showed that VfNF-YB family genes are highly homologous to GmNF-YB genes, and many of them are closely related to functionally characterized NF-YBs. In expression analyses of various tissues (root, stem, leaf, and kernel) and the root during pathogen infection, VfNF-YB1, 5, and 11 were dominantly expressed in kernels, and VfNF-YB7 and 9 were expressed only in the root. Different VfNF-YB family genes showed different responses to pathogen infection, suggesting that they play different roles in the pathogen response. Together, these findings represent the first extensive evaluation of the NF-YB family in tung tree and provide a foundation for dissecting the functions of VfNF-YB genes in seed development, stress adaption, fatty acid synthesis, and pathogen response.

Overexpression of the poplar NF-YB7 transcription factor confers drought tolerance and improves water-use efficiency in Arabidopsis.

Water deficit is a serious environmental factor limiting the growth and productivity of plants worldwide. Improvement of drought tolerance and efficient water use are significant strategies to overcome this dilemma. In this study, a drought-responsive transcription factor, nuclear factor Y subunit B 7 (PdNF-YB7), induced by osmotic stress (PEG6000) and abscisic acid, was isolated from fast-growing poplar clone NE-19 [Populus nigra × (Populus deltoides × Populus nigra)]. Ectopic overexpression of PdNF-YB7 (oxPdB7) in Arabidopsis enhanced drought tolerance and whole-plant and instantaneous leaf water-use efficiency (WUE, the ratio of biomass produced to water consumed). Overexpressing lines had an increase in germination rate and root length and decrease in water loss and displayed higher photosynthetic rate, instantaneous leaf WUE, and leaf water potential to exhibit enhanced drought tolerance under water scarcity. Additionally, overexpression of PdNF-YB7 in Arabidopsis improved whole-plant WUE by increasing carbon assimilation and reducing transpiration with water abundance. These drought-tolerant, higher WUE transgenic Arabidopsis had earlier seedling establishment and higher biomass than controls under normal and drought conditions. In contrast, Arabidopsis mutant nf-yb3 was more sensitive to drought stress with lower WUE. However, complementation analysis indicated that complementary lines (nf-yb3/PdB7) had almost the same drought response and WUE as wild-type Col-0. Taken together, these results suggest that PdNF-YB7 positively confers drought tolerance and improves WUE in Arabidopsis; thus it could potentially be used in breeding drought-tolerant plants with increased production even under water deficiency.

Transcription factors NF-YB involved in embryogenesis and hormones responses in Dimocarpus Longan Lour.

Introduction: NF-YB transcription factor is an important regulatory factor in plant embryonic development. Results: In this study, 15 longan NF-YB (DlNF-YB) family genes were systematically identified in the whole genome of longan, and a comprehensive bioinformatics analysis of DlNF-YB family was performed. Comparative transcriptome analysis of DlNF-YBs expression in different tissues, early somatic embryogenesis (SE), and under different light and temperature treatments revealed its specific expression profiles and potential biological functions in longan SE. The qRT-PCR results implied that the expression patterns of DlNF-YBs were different during SE and the zygotic embryo development of longan. Supplementary 2,4-D, NPA, and PP333 in longan EC notably inhibited the expression of DlNF-YBs; ABA, IAA, and GA3 suppressed the expressions of DlNF-YB6 and DlNF-YB9, but IAA and GA3 induced the other DlNF-YBs. Subcellular localization indicated that DlNF-YB6 and DlNF-YB9 were located in the nucleus. Furthermore, verification by the modified 5'RNA Ligase Mediated Rapid Amplification of cDNA Ends (5' RLM-RACE) method demonstrated that DlNF-YB6 was targeted by dlo-miR2118e, and dlo-miR2118e regulated longan somatic embryogenesis (SE) by targeting DlNF-YB6. Compared with CaMV35S- actuated GUS expression, DlNF-YB6 and DlNF-YB9 promoters significantly drove GUS expression. Meanwhile, promoter activities were induced to the highest by GA3 but suppressed by IAA. ABA induced the activities of the promoter of DlNF-YB9, whereas it inhibited the promoter of DlNF-YB6. Discussion: Hence, DlNF-YB might play a prominent role in longan somatic and zygotic embryo development, and it is involved in complex plant hormones signaling pathways.

Cdc25B is transcriptionally inhibited by IER5 through the NF-YB transcription factor in irradiation-treated HeLa cells.

Cervical cancer (CC) is a type of pelvic malignant tumor that severely threatens women's health. Current evidence suggests that IER5, as a potential radiosensitizer, promotes irradiation-induced apoptosis in CC tissues in patients undergoing chemoradiotherapy. IER5 has been shown to be involved in the G2/M-phase transition. In the present study, we used Cdc25B as the breakthrough point to explore the underlying mechanism of IER5 in the cell cycle regulation of radiation-damaged HeLa cells. IER5 was evidently upregulated after irradiation, but Cdc25B was significantly downregulated. In monoclonal IER5-silenced HeLa cells, irradiation-induced downregulation of Cdc25B was attenuated. The effect of irradiation on Cdc25B promoter activity was determined by dual-luciferase reporter assays. The response elements on the Cdc25B promoter related to irradiation were predicted by JASPAR. These conserved sequences were mutated individually or in combination by splicing-by-overlap extension PCR, and their function was confirmed by dual-luciferase reporter assays. The enrichment efficiency of transcription factors after irradiation was determined by chromatin immunoprecipitation (ChIP) assay. Both Sp1/Sp3 and NF-YB binding sites were involved in irradiation-mediated regulation of Cdc25B. IER5 was involved in irradiation-mediated regulation of Cdc25B through the NF-YB binding site. Furthermore, ChIP assays showed that IER5 bound to the Cdc25B promoter, and the binding of IER5 to the Cdc25B promoter region in irradiation-induced HeLa cells induced the release of the coactivator p300 through interaction with NF-YB. Taken together, these findings indicate that IER5 is the transcriptional repressor that accelerates the downregulation of Cdc25B expression after irradiation.

NF-YB-Mediated Active Responses of Plant Growth under Salt and Temperature Stress in Eucalyptus grandis.

The transcription factor NF-YB (nuclear factor-YB) family is a subfamily of the nuclear factor Y (NF-Y), which plays an important role in regulating plant growth, development and participates in various stress responses. Although the NF-Y family has been studied in many species, it is still obscure in Eucalyptus grandis. In this study, 23 EgNF-YB genes in eucalyptus were identified and unevenly distributed on 11 chromosomes. Phylogenetic analysis showed the EgNF-YB genes were divided into two clades, LEC-1 type and non-LEC1 type. The evolution of distinct clades was relatively conservative, the gene structures were analogous, and the differences of genetic structures among clades were small. The expression profiles showed that the distinct EgNF-YB genes were highly expressed in diverse tissues, and EgNF-YB4/6/13/19/23 functioned in response to salinity, heat and cold stresses. Our study characterized the phylogenetic relationship, gene structures and expression patterns of EgNF-YB gene family and investigated their potential roles in abiotic stress responses, which provides solid foundations for further functional analysis of NF-YB genes in eucalyptus.

Isolation, characterization and expression analysis of stress responsive plant nuclear transcriptional factor subunit (NF-YB2) from commercial Saccharum hybrid and wild relative Erianthus arundinaceus.

Plant nuclear factor (NF-Y) is a transcription activating factor, consisting of three subunits, and plays a key regulatory role in many stress-responsive mechanisms including drought and salinity stresses. NF-Ys function both as complex and individual subunits. Considering the importance of sugarcane as a commercial crop with high socio-economic importance and the crop being affected mostly by water deficit stress and salinity stress causing significant yield loss, nuclear transcriptional factor NF-YB2 was focused in this study. Plant nuclear factor subunit B2 from Erianthus arundinaceus (EaNF-YB2), a wild relative of sugarcane which is known for its drought and salinity stress tolerance, and commercial Saccharum hybrid Co 86032 (ShNF-YB2) was isolated and characterized. Both EaNF-YB2 and ShNF-YB2 genes are 543 bp long that encodes for a polypeptide of 180 amino acid residues. Comparison of EaNF-YB2 and ShNF-YB2 gene sequences revealed nucleotide substitutions at nine positions corresponding to three synonymous and six nonsynonymous amino acid substitutions that resulted in variations in physiochemical properties. However, multiple sequence alignment (MSA) of NF-YB2 proteins showed conservation of functionally important amino acid residues. In silico analysis revealed NF-YB2 to be a hydrophilic and intracellular protein, and EaNF-YB2 is thermally more stable than that of ShNF-YB2. Phylogenetic analysis suggested the lower rate of evolution of NF-YB2. Subcellular localization in sugarcane callus revealed NF-YB2 localization at nucleus that further evidenced it to be a transcription activation factor. Comparative RT-qPCR experiments showed a significantly higher level of NF-YB2 expression in E. arundinaceus when compared to that in the commercial Saccharum hybrid Co 86032 under drought and salinity stresses. Hence, EaNF-YB2 could be an ideal candidate gene, and its overexpression in sugarcane through genetic engineering approach might enhance tolerance to drought and salinity stresses.

Regulation and evolution of the interaction of the seed B3 transcription factors with NF-Y subunits.

The LAFL genes (LEC2, ABI3, FUS3, LEC1) encode transcription factors that regulate different aspects of seed development, from early to late embryogenesis and accumulation of storage compounds. These transcription factors form a complex network, with members able to interact with various other players to control the switch between embryo development and seed maturation and, at a later stage in the plant life cycle, between the mature seed and germination. In this review, we first summarize our current understanding of the role of each member in the network in the light of recent advances regarding their regulation and structure/function relationships. In a second part, we discuss new insights concerning the evolution of the LAFL genes to address the more specific question of the conservation of LEAFY COTYLEDONS 2 in both dicots and monocots and the putative origin of the network. Last we examine the current major limitations to current knowledge and future prospects to improve our understanding of this regulatory network.

Overexpression of a NF-YB3 transcription factor from Picea wilsonii confers tolerance to salinity and drought stress in transformed Arabidopsis thaliana.

Nuclear factor Y (NF-Y) is a highly conserved transcription factor comprising NF-YA, NF-YB and NF-YC subunits. To date, the roles of NF-Y subunit in plant still remain elusive. In this study, a subunit NF-YB (PwNF-YB3), was isolated from Picea wilsonii Mast. and its role was studied. PwNF-YB3 transcript was detected in all vegetative and reproductive tissues with higher levels in stem and root and was greatly induced by salinity, heat and PEG but not by cold and ABA treatment. Over-expression of PwNF-YB3 in Arabidopsis showed a significant acceleration in the onset of flowering and resulted in more vigorous seed germination and significant tolerance for seedlings under salinity, drought and osmotic stress compared with wild type plants. Transcription levels of salinity-responsive gene (SOS3) and drought-induced gene (CDPK1) were substantially higher in transgenic Arabidopsis than in wild-type plants. Importantly, CBF pathway markers (COR15B, KIN1, LEA76), but not ABA pathway markers CBF4, were greatly induced under condition of drought. The nuclear localization showed that NF-YB3 acted as a transcription factor. Taken together, the data provide evidence that PwNF-YB3 positively confers significant tolerance to salt, osmotic and drought stress in transformed Arabidopsis plants probably through modulating gene regulation in CBF-dependent pathway.

OsNF-YB1, a rice endosperm-specific gene, is essential for cell proliferation in endosperm development.

Cell cycle regulators are crucial for normal endosperm development and seed size determination. However, how the cell cycle related genes regulate endosperm development remains unclear. In this study, we reported a rice Nuclear Factor Y (NF-Y) gene OsNF-YB1, which was also identified as an endosperm-specific gene. Transcriptional profiling and promoter analysis revealed that OsNF-YB1 was highly expressed at the early stages of rice endosperm development (5-7 DAP, days after pollination). Repression of OsNF-YB1 resulted in differential expression of the genes in cell cycle pathway, which caused abnormal seeds with defected embryo and endosperm. Basic cytological analysis demonstrated that the reduced endosperm cell numbers disintegrated with the development of those abnormal seeds in OsNF-YB1 RNAi plants. Taken together, these results suggested that the endosperm-specific gene OsNF-YB1 might be a cell cycle regulator and played a role in maintaining the endosperm cell proliferation.

LEC1-LIKE paralog transcription factor: how to survive extinction and fit in NF-Y protein complex.

Transcription factor function is crucial for eukaryotic systems. The presence of transcription factor families in genomes represents a significant technical challenge for functional studies. To understand their function, we must understand how they evolved and maintained by organisms. Based on genome scale searches for homologs of LEAFY COTYLEDON-LIKE (L1L; AtNF-YB6), NF-YB transcription factor, we report the discovery and annotation of a complete repertoire of thirteen novel genes that belong to the L1L paralogous gene family of Solanum lycopersicum. Gene duplication events within the species resulted in the expansion of the L1L family. Sequence and structure-based phylogenetic analyses revealed two distinct groups of L1Ls in tomato. Natural selection appears to have contributed to the asymmetric evolution of paralogs. Our results point to key differences among SlL1L paralogs in the presence of motifs, structural features, cysteine composition and expression patterns during plant and fruit development. Furthermore, differences in the binding domains of L1L members suggest that some of them evolved new binding specificities. These results reveal dramatic functional diversification of L1L paralogs for their maintenance in tomato genome. Our comprehensive insights on tomato L1L family should provide the basis for further functional and genetic experimentation.

Nuclear transcription factor Y and its roles in cellular processes related to human disease.

Nuclear transcription factor Y (NF-Y) is an example of a transcriptional regulation factor in eukaryotes consisting of three different subunits, NF-YA, NF-YB and NF-YC, which are all necessary for formation of NF-Y complexes and binding to CCAAT boxes in promoters of its target genes. Highly conserved between human and Drosophila, NF-Y regulates transcription of various genes related to the cell cycle and various human diseases. Drosophila models have been widely used as tools for studying genetics and developmental biology and more recently for analyzing the functions of human disease genes, including those responsible for developmental and neurological disorders, cancer, cardiovascular disease and metabolic and storage diseases, as well as genes required for function of the visual, auditory and immune systems. In this review, in vivo findings from Drosophila models relevant to the roles of NF-Y in various human diseases are summarized. Recent studies have demonstrated novel contributions of dNF-Y to apoptosis and apoptosis-induced proliferation, and in photoreceptor cell differentiation during the development of the Drosophila compound eye.