FLC Expression Research Articles

Divergent Flowering Time Responses to Increasing Temperatures Are Associated With Transcriptome Plasticity and Epigenetic Modification Differences at FLC Promoter Region of Arabidopsis thaliana.

Understanding the genetic, and transcriptomic changes that drive the phenotypic plasticity of fitness traits is a central question in evolutionary biology. In this study, we utilised 152 natural Swedish Arabidopsis thaliana accessions with re-sequenced genomes, transcriptomes and methylomes and measured flowering times (FTs) under two temperature conditions (10°C and 16°C) to address this question. We revealed that the northern accessions exhibited advanced flowering in response to decreased temperature, whereas the southern accessions delayed their flowering, indicating a divergent flowering response. This contrast in flowering responses was associated with the isothermality of their native ranges, which potentially enables the northern accessions to complete their life cycle more rapidly in years with shorter growth seasons. At the transcriptome level, we observed extensive rewiring of gene co-expression networks, with the expression of 25 core genes being associated with the mean FT and its plastic variation. Notably, variations in FLC expression sensitivity between northern and southern accessions were found to be associated with the divergence FT response. Further analysis suggests that FLC expression sensitivity is associated with differences in CG, CHG and CHH methylation at the promoter region. Overall, our study revealed the association between transcriptome plasticity and flowering time plasticity among different accessions, providing evidence for its relevance in ecological adaptation. These findings offer deeper insights into the genetics of rapid responses to environmental changes and ecological adaptation.

The PHYB–FOF2–VOZ2 module functions to fine-tune flowering in response to changes in light quality by modulating FLC expression in Arabidopsis

Proper timing of flowering under different environmental conditions is critical for plant propagation. Light quality is a pivotal environmental cue that plays a critical role in flowering regulation. Plants tend to flower late under light with a high red (R)/far-red (FR) light ratio but early under light with a low R/FR light ratio. However, how plants fine-tune flowering in response to changes in light quality is not well understood. Here, we demonstrate that F-box of Flowering 2 (FOF2), an autonomous pathway–related regulator, physically interacts with VASCULAR PLANT ONE-ZINC FINGER 1 and 2 (VOZ1 and VOZ2), which are direct downstream factors of the R/FR light receptor phytochrome B (PHYB). We show that PHYB physically interacts with FOF2, mediates stabilization of the FOF2 protein under FR light and end-of-day FR light, and enhances FOF2 binding to VOZ2, which leads to degradation of VOZ2 by SCFFOF2 E3 ligase. By contrast, PHYB mediates degradation of FOF2 protein under R light and end-of-day R light. Genetic interaction studies demonstrated that FOF2 functions downstream of PHYB to promote FLC expression and inhibit flowering under both high R/FR light and simulated shade conditions, processes that are partially dependent on VOZ proteins. Taken together, our findings suggest a novel mechanism whereby plants fine-tune flowering time through a PHYB–FOF2–VOZ2 module that modulates FLC expression in response to changes in light quality.

Mechanisms of ferroptosis in hypoxic-ischemic brain damage in neonatal rats

This study was to explore the mechanism of ferroptosis and hypoxic-ischemic brain damage in neonatal rats. The neonatal rat hypoxic-ischemic brain damage (HIBD) model was established using the Rice-Vannucci method and treated with the ferroptosis inhibitor liproxstatin-1. Cognitive assessment was performed through absentee field experiments to confirm the successful establishment of the model. Brain tissue damage was evaluated by comparing regional cerebral blood flow and quantifying tissue staining. Neuronal cell morphological changes in the rats' cortical and hippocampal regions were observed using HE and Nissl staining. ELISA was performed to determine GPX4, GSH and ROS expression levels in the rats' brain tissues, and Western blotting to assess the expression levels of 4-HNE, GPX4, GSS, ACSL4, SLC7A11, SLC3A2, TFRC, FHC, FLC, HIF-1α, and Nrf2 proteins in rat brain tissues. Compared to the Sham group, the HIBD group exhibited a significant decrease in cerebral blood perfusion, reduced brain nerve cells, and disordered cell arrangement. The use of the ferroptosis inhibitor effectively improved brain tissue damage and preserved the shape and structure of nerve cells. The oxidative stress products ROS and 4-HNE in the brain tissue of the HIBD group increased significantly, while the expression of antioxidant indicators GPX4, GSH, SLC7A11, and GSS decreased significantly. Furthermore, the expression of iron metabolism-related proteins TFRC, FHC, and FLC increased significantly, whereas the expression of the ferroptosis-related transcription factors HIF-1α and Nrf2 decreased significantly. Treatment with liproxstatin-1 exhibited therapeutic effects on HIBD and downregulated tissue ferroptosis levels. This study shows the involvement of ferroptosis in hypoxic-ischemic brain damage in neonatal rats through the System Xc−-GSH-GPX4 functional axis and iron metabolism pathway, with the HIF-1α and Nrf2 transcription factors identified as the regulators of ferroptosis involved in the HIBD process in neonatal rats.

The Arabidopsis RRM domain proteins EDM3 and IBM2 coordinate the floral transition and basal immune responses.

The transition from vegetative to reproductive development (floral transition) is a costly process in annual plants requiring increased investments in metabolic resources. The Arabidopsis thaliana (Arabidopsis) PHD finger protein EDM2 and RRM domain proteins EDM3 and IBM2 are known to form chromatin-associated complexes controlling transcript processing. We are reporting that distinct splice isoforms of EDM3 and IBM2 cooperate in the coordination of the floral transition with basal immune responses. These cooperating splice isoforms, termed EDM3L and IBM2L, control the intensity of basal immunity and, via a separate pathway, the timing of the floral transition. During the developmental phase prior to the floral transition expression of EDM3L and IBM2L strongly and gradually increases, while these isoforms simultaneously down-regulate expression of the floral suppressor gene FLC and promote the transition to reproductive growth. At the same time these accumulating EDM3 and IBM2 splice isoforms gradually suppress basal immunity against the virulent Noco2 isolate of the pathogenic oomycete Hyaloperonospora arabidopsidis and down-regulate expression of a set of defense-associated genes and immune receptor genes. We are providing clear evidence for a functional link between the floral transition and basal immunity in the annual plant Arabidopsis. Coordination of these two biological processes, which compete for metabolic resources, is likely critical for plant survival and reproductive success.

Methylome and transcriptome analysis of flowering branches building of Citrus plants induced by drought stress

Citrus plants exhibit positive floral response under water stress conditions, however, the mechanistic understanding of floral induction remains largely unexplored in water deficit. In this study, DNA methylomic and transcriptomic analyses were integrated to explore the flowering bud formation as well as branches building after light drought stress. While comparing with the conventional watering group (CK), the light drought group treated with five months (LD) showed a significant increase in the flowering branches, whereas an apparent decrease in vegetative branches. Global DNA methylation analysis showed that the LD Group acquired DNA methylation in more than 70,090 genomic regions and lost DNA methylation in about 18,421 genomic regions compared with normal watering group, this indicates that water deficiency leads to a global increase in the expression of DNA methylation in citrus. In the same time, we verified that the increase of DNA methylation level in LD group was correlated with the decrease of DNA demethylase related gene expression.Interestingly, in transcription analysis, it was found that the promoting flower genes of the LD group did not increase but decreased similarly with repressing genes, which is contrary to the intended result. Thus, we thought the lower expression of suppressors FLC and BFT were the key influencing factor to stimulate the flowering branches formation after LD treatment. Moreover, there was a strong negative correlation between the genes expression level and methylation level of the flowering induction/flower development genes. In general, we thought high global DNA methylation level induced by water deficit regulate the flowering branches building by reducing FLC and BFT genes expression.

BraVRG, a novel protein of Brassica rapa, is induced by vernalization and promotes flowering in Arabidopsis thaliana

Plant flowering is an important economical characteristic for the transformation from vegetative growth to reproductive growth, especially for biennial crops. Additionally, bolting or flowering time is more important for vegetable plants due to their different harvest organs, such as flower for cauliflower and broccoli and leafy heads for cabbage and Chinese cabbage. The flowering time of Arabidopsis thaliana has six classical regulated pathways, and some key regulated genes are identified in Brassicaceae crops. However, the regulatory mechanism needs further exploration. Here, we reported an novel protein BraVRG (Vernalization Related Gene) of Chinese cabbage induced by vernalization. The expression of BraVRG increased rapidly at 14 day of vernalization in the semi-winter type of Brassica rapa and 21 days for the winter types. Meanwhile the modifications of H3K4me3 deposited on BraVRG increased but H3K27me3 decreased. Moreover, BraVRG promoted flowering in transgenic A. thaliana compared with the wild types accompanied the downregulated expression of FLC caused by the decrease of H3K4me3 enrichment and the increase of H3K27me3 on FLC with or without vernalization conditions.

Characterization of an autonomous pathway complex that promotes flowering in Arabidopsis.

Although previous studies have identified several autonomous pathway components that are required for the promotion of flowering, little is known about how these components cooperate. Here, we identified an autonomous pathway complex (AuPC) containing both known components (FLD, LD and SDG26) and previously unknown components (EFL2, EFL4 and APRF1). Loss-of-function mutations of all of these components result in increased FLC expression and delayed flowering. The delayed-flowering phenotype is independent of photoperiod and can be overcome by vernalization, confirming that the complex specifically functions in the autonomous pathway. Chromatin immunoprecipitation combined with sequencing indicated that, in the AuPC mutants, the histone modifications (H3Ac, H3K4me3 and H3K36me3) associated with transcriptional activation are increased, and the histone modification (H3K27me3) associated with transcriptional repression is reduced, suggesting that the AuPC suppresses FLC expression at least partially by regulating these histone modifications. Moreover, we found that the AuPC component SDG26 associates with FLC chromatin via a previously uncharacterized DNA-binding domain and regulates FLC expression and flowering time independently of its histone methyltransferase activity. Together, these results provide a framework for understanding the molecular mechanism by which the autonomous pathway regulates flowering time.

Regulatory Networks of Flowering Genes in Angelica sinensis during Vernalization.

Angelica sinensis is a low-temperature and long-day perennial herb that has been widely used for cardio-cerebrovascular diseases in recent years. In commercial cultivation, up to 40% of flowering decreases the officinal yield of roots and accumulation of bioactive compounds. Although the regulatory mechanism of flowering genes during the photoperiod has been revealed, the networks during vernalization have not been mapped. Here, transcriptomics profiles of A. sinensis with uncompleted (T1), completed (T2) and avoided vernalization (T3) were performed using RNA-seq, and genes expression was validated with qRT-PCR. A total of 61,241 isoforms were annotated on KEGG, KOG, Nr and Swiss-Prot databases; 4212 and 5301 differentially expressed genes (DEGs) were observed; and 151 and 155 genes involved in flowering were dug out at T2 vs. T1 and T3 vs. T1, respectively. According to functional annotation, 104 co-expressed genes were classified into six categories: FLC expression (22; e.g., VILs, FCA and FLK), sucrose metabolism (12; e.g., TPSs, SUS3 and SPSs), hormone response (18; e.g., GID1B, RAP2s and IAAs), circadian clock (2; i.e., ELF3 and COR27), downstream floral integrators and meristem identity (15; e.g., SOC1, AGL65 and SPLs) and cold response (35; e.g., PYLs, ERFs and CORs). The expression levels of candidate genes were almost consistent with FPKM values and changes in sugar and hormone contents. Based on their functions, four pathways that regulate flowering during vernalization were mapped, including the vernalization pathway, the autonomic pathway, the age pathway and the GA (hormone) pathway. This transcriptomic analysis provides new insights into the gene-regulatory networks of flowering in A. sinensis.

MicroRNA miR394 regulates flowering time in Arabidopsis thaliana.

miR394 regulates Arabidopsis flowering time in a LCR-independent manner. Arabidopsis plants harboring mutations in theMIR394 genes exhibit early flowering, lower expression of floral repressor FLC and higher expression of floral integrators FT and SOC1. Plant development occurs throughout its entire life cycle and involves a phase transition between vegetative and reproductive phases, leading to the flowering process, fruit formation and ultimately seed production. It has been shown that the microRNA394 (miR394) regulates the accumulation of the transcript coding for LEAF CURLING RESPONSIVENESS, a member of a family of F-Box proteins. The miR394 pathway regulates several processes including leaf morphology and development of the shoot apical meristem during embryogenesis, as well as having been assigned a role in the response to biotic and abiotic stress in Arabidopsis thaliana and other species. Here, we characterized plants harboring mutations in MIR394 precursor genes and demonstrate that mir394a mir394b double mutants display an early flowering phenotype which correlates with a lower expression of FLOWERING LOCUS C earlier in development and higher expression of the floral integrators FLOWERING LOCUS T and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1. Consequently, mutant plants produce fewer branches and exhibit lower seed production. Our work reveals previously unknown developmental aspects regulated by the miR394 pathway, in an LCR-independent manner, contributing to the characterization of the multiple roles of this versatile plant regulatory miRNA.

MSI1 and HDA6 function interdependently to control flowering time via chromatin modifications.

MULTICOPY SUPPRESSOR OF IRA1 (MSI1) is a conserved subunit of Polycomb Repressive Complex 2 (PRC2), which mediates gene silencing by histone H3 lysine 27 trimethylation (H3K27Me3). Here, we demonstrated that MSI1 interacts with the RPD3-like histone deacetylase HDA6 both invitro and invivo. MSI1 and HDA6 are involved in flowering and repress the expression of FLC, MAF4, and MAF5 by removing H3K9 acetylation but adding H3K27Me3. Chromatin immunoprecipitation analysis showed that HDA6 and MSI1 interdependently bind to the chromatin of FLC, MAF4, and MAF5. Furthermore, H3K9 deacetylation mediated by HDA6 is dependent on MSI1, while H3K27Me3 mediated by PRC2 containing MSI1 is also dependent on HDA6. Taken together, these data indicate that MSI1 and HDA6 act interdependently to repress the expression of FLC, MAF4, and MAF5 through histone modifications. Our findings reveal that the HDA6-MSI1 module mediates the interaction between histone H3 deacetylation and H3K27Me3 to repress gene expression involved in flowering time control.

A domesticated Harbinger transposase forms a complex with HDA6 and promotes histone H3 deacetylation at genes but not TEs in Arabidopsis.

In eukaryotes, histone acetylation is a major modification on histone N-terminal tails that is tightly connected to transcriptional activation. HDA6 is a histone deacetylase involved in the transcriptional regulation of genes and transposable elements (TEs) in Arabidopsis thaliana. HDA6 has been shown to participate in several complexes in plants, including a conserved SIN3 complex. Here, we uncover a novel protein complex containing HDA6, several Harbinger transposon-derived proteins (HHP1, SANT1, SANT2, SANT3, and SANT4), and MBD domain-containing proteins (MBD1, MBD2, and MBD4). We show that mutations of all four SANT genes in the sant-null mutant cause increased expression of the flowering repressors FLC, MAF4, and MAF5, resulting in a late flowering phenotype. Transcriptome deep sequencing reveals that while the SANT proteins and HDA6 regulate the expression of largely overlapping sets of genes, TE silencing is unaffected in sant-null mutants. Our global histone H3 acetylation profiling shows that SANT proteins and HDA6 modulate gene expression through deacetylation. Collectively, our findings suggest that Harbinger transposon-derived SANT domain-containing proteins are required for histone deacetylation and flowering time control in plants.

Molecular variation in a functionally divergent homolog of FCA regulates flowering time in Arabidopsis thaliana

The identification and functional characterization of natural variants in plants are essential for understanding phenotypic adaptation. Here we identify a molecular variation in At2g47310 that contributes to the natural variation in flowering time in Arabidopsis thaliana accessions. This gene, which we term SISTER of FCA (SSF), functions in an antagonistic manner to its close homolog FCA. Genome-wide association analysis screens two major haplotypes of SSF associated with the natural variation in FLC expression, and a single polymorphism, SSF-N414D, is identified as a main contributor. The SSF414N protein variant interacts more strongly with CUL1, a component of the E3 ubiquitination complex, than the SSF414D form, mediating differences in SSF protein degradation and FLC expression. FCA and SSF appear to have arisen through gene duplication after dicot-monocot divergence, with the SSF-N414D polymorphism emerging relatively recently within A. thaliana. This work provides a good example for deciphering the functional importance of natural polymorphisms in different organisms.

Homeologs of Brassica SOC1, a central regulator of flowering time, are differentially regulated due to partitioning of evolutionarily conserved transcription factor binding sites in promoters

Evolution of Brassica genome post-polyploidization reveals asymmetrical genome fractionation and copy number variation. Herein, we describe the impact of promoter divergence among SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) homeologs on expression and function in Brassica spp. SOC1, a regulated floral pathway integrator, is conserved as 3 redundant homeologs in diploid Brassicas. Even with high sequence identity within coding regions (92.8–100%), the spatio-temporal expression patterns of 9 SOC1 homologs in B. juncea and B. nigra indicates regulatory divergence. While LF and MF2 SOC1 homeologs are upregulated during floral transition, MF1 is barely expressed. Also, MF2 homeolog levels do not decline post-flowering, unlike LF. To investigate the underlying source of divergence, we analyzed the sequence and phylogeny of all reported (22) and isolated (21) upstream regions of Brassica SOC1. Full length upstream regions (4712–19189 bp) reveal 5 ubiquitously conserved ancestral Blocks, harboring binding sites of 18 TFs (TFBSs) characterized in Arabidopsis thaliana. The orthologs of these TFBSs are differentially conserved among Brassica SOC1 homeologs, imparting expression divergence. No crucial TFBSs are exclusively lost from LF_SOC1 promoter, while MF1_SOC1 has lost NF-Y binding site crucial for SOC1 activation by CONSTANS. MF2_SOC1 homeologs have lost important TFBSs (SEP3, AP1 and SMZ), responsible for SOC1 repression post-flowering. BjuAALF_SOC1 promoter (proximal 2 kb) shows ubiquitous reporter expression in B. juncea cv. Varuna transgenics, while BjuAAMF1_SOC1 promoter shows absence of reporter expression, validating the impact of TFBS divergence. Conservation of the original primary protein sequence is discovered in B. rapa homeologs (46) of 18 TFs. Co-regulation pattern of these TFs appeared similar for B. rapa LF and MF2 SOC1 homeologs; MF1 shows significant variation. Strong regulatory association is recorded for AP1, AP2, SEP3, FLC and CONSTANS/NF-Y, highlighting their importance in homeolog-specific SOC1 regulation. Correlation of B. juncea AP1, AP2 and FLC expression with SOC1 homeologs also complies with the TFBS differences. We thus conclude that redundant SOC1 loci contribute differentially to cumulative expression of SOC1 due to divergent selection of ancestral TFBSs.

The FACT Histone Chaperone: Tuning Gene Transcription in the Chromatin Context to Modulate Plant Growth and Development.

FACT is a heterodimeric histone chaperone consisting of the SSRP1 and SPT16 proteins and is conserved among eukaryotes. It interacts with the histones H2A-H2B and H3-H4 as well as with DNA. Based on in vitro and in vivo studies mainly in yeast and mammalian cells, FACT can mediate nucleosome disassembly and reassembly and thus facilitates in the chromatin context DNA-dependent processes including transcription, replication and repair. In plants, primarily the role of FACT related to RNA polymerase II transcription has been examined. FACT was found to associate with elongating Arabidopsis RNA polymerase II (RNAPII) as part of the transcript elongation complex and it was identified as repressor of aberrant intragenic transcriptional initiation. Arabidopsis mutants depleted in FACT subunits exhibit various defects in vegetative and reproductive development. Strikingly, FACT modulates important developmental transitions by promoting expression of key repressors of these processes. Thus, FACT facilitates expression of DOG1 and FLC adjusting the switch from seed dormancy to germination and from vegetative to reproductive development, respectively. In the central cell of the female gametophyte, FACT can facilitate DNA demethylation especially within heterochromatin, and thereby contributes to gene imprinting during Arabidopsis reproduction. This review discusses results particularly from the plant perspective about the contribution of FACT to processes that involve reorganisation of nucleosomes with a main focus on RNAPII transcription and its implications for diverse areas of plant biology.

Changes in FLC and VIN3 Expression during Vernalization of Arabidopsisthaliana Plants from Northern Natural Populations

Specific expression patterns of the FLC and VIN3 genes, which play a key role in the vernalization-mediated transition to flowering of A. thaliana plants from northern natural populations (Karelia), have been revealed. The differences in the FLC and VIN3 expression patterns during vernalization for populations represented by late-flowering forms, on one hand, and a population which was mixed with respect to the onset of flowering, on the other hand, were observed. A low level of FLC and VIN3 expression in plants from the studied populations prior to cold exposure was established. During vernalization, the FLC mRNA levels increased on the 10th and 20th day, followed by its decrease by the 30th day. Prolonged exposure to cold caused an increase in VIN3 expression with a peak in the populations represented by late-flowering plant forms on the 30th day of vernalization and in the mixed population for the flowering onset of plants on the 40th day. Specific patterns of FLC and VIN3 expression during vernalization was observed in S1 offspring of one early-flowering plant, while FLC expression in it changed according to classical scheme; i.e., the initially high level of FLC expression decreased in the process of vernalization. It is suggested that genetic and epigenetic mechanisms involved in controlling the flowering rate and the genes involved in this process may differ in plants from populations of different geographic regions.

Nitrate Transporter 1.1 is involved in regulating flowering time via transcriptional regulation of FLOWERING LOCUS C in Arabidopsis thaliana

Nitrate Transporter 1.1 (NRT1.1) is a nitrate transporter and sensor that modulates plant metabolism and growth. It has previously been shown that NRT1.1 is involved in the regulation of flowering time in Arabidopsis thaliana. In this study, we mainly used genetic and molecular methods to reveal the key flowering pathway that NRT1.1 may be involved in. Mutant alleles of CO and FLC, two crucial components in the flowering pathway, were introduced into the NRT1.1 defective mutant background by crossing. When the CO mutation was introduced into chl1-5 plants, the double mutant had delayed flowering time, and the CO transcription levels did not change in the chl1-5 plants. These results indicate that the CO-dependent photoperiod may be not associated with the delayed flowering shown by chl1-5. However, FLC loss of function could rescue the late flowering phenotype of the chl1-5 mutant, and FLC expression levels significantly increased in the NRT1.1 defective mutant plants. The FT expression levels in the chl1-5flc-3 double mutant plants recovered when the FLC mutation was introduced into chl1-5 plants and the up-regulation of FLC transcripts in the chl1-5 mutant plants was not related to nitrate availability. Our findings suggest that NRT1.1 affects flowering time via interaction with the FLC-dependent flowering pathway to influence its target gene FT, and that NRT1.1 may be included in an additional signaling pathway that represses the expression of FLC in a nitrate-independent manner.

PHD type zinc finger protein PFP represses flowering by modulating FLC expression in Arabidopsis thaliana

FLC is an integrative regulator of flowering in Arabidopsis thaliana. The expression of FLC gene is regulated by epigenetic control via histone modification. Plant homeodomain (PHD) finger is a sequence-specific histone binding motif evolutionary conserved in eukaryotes. It has been known that PHD finger proteins play a significant role as a regulator of epigenetic gene expression. In this study, we investigated the role of an Arabidopsis PHD finger protein homolog, named PFP (PHD finger domain containing protein). Phenotypic analysis using a loss-of-function line of PFP (SALK_034619) showed early flowering as compared with the control (Col-0) under long-day condition that promotes flowering, suggesting that PFP is essential in the flowering repression of Arabidopsis. The analyses of major flowering regulatory gene expressions (FLC, FT, CO, FCA, FLK, FLV, EBS, TFL2) indicated that the expression of floral repressor FLC was decreased, while the one of floral inducer FT was increased in the SALK_034619. On the contrary, in the transgenic Arabidopsis overexpressing PFP, the flowering time was delayed and the expression pattern of flowering regulatory genes was reversed in which FLC was upregulated and FT was downregulated, suggesting that PFP is sufficient to regulate flowering regulatory genes. Based on these results, we conclude that PFP controls flowering time by suppressing the upstream of major flowering regulatory genes via FLC expression in Arabidopsis.

Arabidopsis YAF9 histone readers modulate flowering time through NuA4-complex-dependent H4 and H2A.Z histone acetylation at FLC chromatin.

Posttranslational histone modifications and the dynamics of histone variant H2A.Z are key mechanisms underlying the floral transition. In yeast, SWR1-C and NuA4-C mediate the deposition of H2A.Z and the acetylation of histone H4, H2A and H2A.Z, respectively. Yaf9 is a subunit shared by both chromatin-remodeling complexes. The significance of the two Arabidopsis YAF9 homologues, YAF9A and YAF9B, is unknown. To get an insight into the role of Arabidopsis YAF9 proteins in plant developmental responses, we followed physiological, genetic, genomic, epigenetic, proteomics and cell biology approaches. Our data revealed that YAF9A and YAF9B are histone H3 readers with unequally redundant functions. Double mutant yaf9a yaf9b plants display pleiotropic developmental phenotypic alterations as well as misregulation of a wide variety of genes. We demonstrated that YAF9 proteins regulate flowering time by both FLC-dependent and independent mechanisms that work in parallel with SWR1-C. Interestingly, we show that YAF9A binds FLC chromatin and that YAF9 proteins regulate FLC expression by modulating the acetylation levels of H2A.Z and H4 but not H2A.Z deposition. Our work highlights the key role exerted by YAF9 homologues in the posttranslational modification of canonical histones and variants that regulate gene expression in plants to control development.

Picea wilsonii transcription factor NAC2 enhanced plant tolerance to abiotic stress and participated in RFCP1-regulated flowering time

Picea wilsonii transcription factor PwNAC2 enhanced plant tolerance to salt and drought stress through multiple signaling pathway and interacted with PwRFCP1 to participate in flowering regulation. NAC is one of the largest transcription factor families in plants, however, its role is not yet fully understood. Here, we identified a transcription factor PwNAC2 in Picea wilsonii, which localized in nucleus with transcriptional activity in C-terminal region and can form homodimer by itself. Expression analysis by real-time PCR showed that PwNAC2 was induced by multiple abiotic stresses and phytohormones stimuli. PwRFCP1 (Resemble-FCA-contain-PAT1 domain), an interaction protein of PwNAC2 was screened via yeast two hybrid. Luciferase complementation assay confirmed the interaction in vivo and bimolecular fluorescence complementation assay showed the interaction in nucleus. PwNAC2 overexpression retarded Arabidopsis hypocotyls growth which is closely related to light, whereas promotion of hypocotyls growth by PwRFCP1 is independent on light. Under drought or salt treatment, overexpression of PwNAC2 in Arabidopsis showed more vigorous seed germination and significant tolerance for seedlings by ROS scavenging, reducing of membrane damage, slower water loss and increased stomatal closure. ABA or CBF-pathway marker genes were substantially higher in PwNAC2 transgenic Arabidopsis. Overexpression of PwRFCP1 promotes flowering in transgenic Arabidopsis, whereas PwNAC2 delayed flowering by altering the expression of FT, SOC1 and FLC. In addtioin, PwRFCP1 overexpression plants showed no higher tolerance to stress treatment than Col-0. Collectively, our results indicate that PwNAC2 enhanced plant tolerance to abiotic stress through multiple signaling pathways and participated in PwRFCP1-regulated flowering time.

Overexpression of CCCH zinc finger protein gene delays flowering time and enhances salt tolerance in Arabidopsis by increasing fatty acid unsaturation

CCCH-type zinc-finger proteins constitute a large family playing key roles during plant development and growth. In the present study, we investigated the involvement of the CCCH-type zinc finger protein of AtZFP1 (At2g25900) in flowering and salt stress response in Arabidopsis. Compared with the wild type (WT), bolting and flowering were delayed in AtZFP1-overexpressing plants. Real-time PCR analysis of floral regulating genes in overexpressing Arabidopsis revealed that enhanced expression of FLC decreased the expressions of FT and SOC1. The Fv/Fm of overexpressing Arabidopsis lines was unchanged under salt stress. In contrast, ΦPSII activity and PSI oxidoreduction decreased in WT, overexpressing and mutant strains under salt stress conditions, with the smallest reduction in these parameters observed in the overexpressing strains. These results suggest that the CCCH zinc-finger protein AtZFP1 primarily controls flowering time by changing the expression of flowering genes under long-day conditions. The overexpression of this protein delayed flowering and increased the content and double-bond index of unsaturated fatty acids. Elevation of unsaturated fatty acid content might play important role in protecting the photosynthetic apparatus and maintaining the membrane function at salt stress by alleviating PSII and PSI photoinhibition.