Isolation and expression analysis of a LEAFY/FLORICAULA homolog and its promoter from London plane (Platanus acerifolia Willd.)

Functional characterization of three TERMINAL FLOWER 1-like genes from Platanus acerifolia

KEY MESSAGE

TFL1-like genes of the basal eudicot Platanus acerifolia have conserved roles in maintaining vegetative growth and inhibiting flowering, but may act through distinct regulatory mechanism. Three TERMINAL FLOWER 1 (TFL1)-like genes were isolated and characterized from London plane tree (Platanus acerifolia). All genes have conserved genomic organization and characteristic of the phosphatidylethanolamine-binding protein (PEBP) family. Sequence alignment and phylogenetic analysis indicated that two genes belong to the TFL1 clade, designated as PlacTFL1a and PlacTFL1b, while another one was grouped in the BFT clade, named as PlacBFT. qRT-PCR analysis showed that all three genes primarily expressed in vegetative phase, but the expression of PlacTFL1a was much higher and wider than that of PlacTFL1b, with the latter only detected at relatively low expression levels in apical and lateral buds in April. PlacBFT was mainly expressed in young stems of adult trees followed by juvenile tissues. Ectopic expression of any TFL1-like gene in Arabidopsis showed phenotypes of delayed or repressed flowering. Furthermore, overexpression of PlacTFL1a gene in petunia also resulted in extremely delayed flowering. In non-flowering 35:PlacTFL1a transgenic petunia plants, the FT-like gene (PhFT) gene was significantly upregulated and AP1 homologues PFG, FBP26 and FBP29 were significantly down-regulated in leaves. Yeast two-hybrid analysis indicated that only weak interactions were detected between PlacTFL1a and PlacFDL, and PlacTFL1a showed no interaction with PhFDL1/2. These results indicated that the TFL1-like genes of Platanus have conserved roles in repressing flowering, but probably via a distinct regulatory mechanism.

Isolation and Functional Characterization of a LEAFY Gene in Mango (Mangifera indica L.)

LEAFY (LFY) plays an important role in the flowering process of plants, controlling flowering time and mediating floral meristem differentiation. Owing to its considerable importance, the mango LFY gene (MiLFY; GenBank accession no. HQ585988) was isolated, and its expression pattern and function were characterized in the present study. The cDNA sequence of MiLFY was 1152 bp, and it encoded a 383 amino acid protein. MiLFY was expressed in all tested tissues and was highly expressed in flowers and buds. Temporal expression analysis showed that MiLFY expression was correlated with floral development stage, and two relative expression peaks were detected in the early stages of floral transition and floral organ differentiation. Moreover, 35S::GFP-MiLFY fusion protein was shown to be localized to the nucleus of cells. Overexpression of MiLFY in Arabidopsis promoted early flowering and the conversion of lateral meristems into terminal flowers. In addition, transgenic plants exhibited obvious morphological changes, such as differences in cauline leaf shape, and the number of lateral branches. When driven by the MiLFY promoter, GFP was highly expressed in leaves, floral organs, stems, and roots, during the flowering period. Exogenous gibberellin (GA3) treatment downregulated MiLFY promoter expression, but paclobutrazol (PPP333) upregulated it. Bimolecular fluorescence complementation (BiFC) assays showed that the MiLFY protein can interact with zinc-finger protein 4 (ZFP4) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (MiSOC1D). Taken together, these results indicate that MiLFY plays a pivotal role in controlling mango flowering, and that it is regulated by gibberellin and paclobutrazol.

PaNAC089 is a membrane-tethered transcription factor (MTTF) that modulates flowering, chlorophyll breakdown and trichome initiation

Flowering and senescence are essential developmental stages of green plants, which are governed by complex molecular regulatory networks. However, the connection between flowering regulation and senescence regulation in London plane tree (Platanus acerifolia ) remains unknown. In this study, we identified a gene PaNAC089 from London plane tree, which encodes a membrane-tethered transcription factor (MTTF) belonging to the NAC (NAM, ATAF1/2, CUC2) transcription factor family. We investigated the functions of PaNAC089 in the regulation of flowering and senescence through the analysis of expression profiles and transgenic phenotypes. Heterologous overexpression of ΔPaNAC089 delayed flowering and inhibited chlorophyll breakdown to produce dark green rosette leaves in Arabidopsis . In addition, the trichome density of rosette leaves was decreased in transgenic lines. In ΔPaNAC089 overexpression plants, a series of functional genes with inhibited expression were identified by quantitative real-time polymerase chain reaction (qRT-PCR), including genes that regulate flowering, chlorophyll decomposition, and trichome initiation. Furthermore, Δ PaNAC089 directly binds to the promoter of CONSTANS (CO ) and NON-YELLOWING2 (NYE2 ) in the yeast one-hybrid assay. Consistent with this, luciferase (LUC) transient expression assays also showed that Δ PaNAC089 could inhibit the activity of NYE2 . To summarise, our data suggests that PaNAC089 is an MTTF that modulates flowering, chlorophyll breakdown and trichome initiation.

Vanilla bahiana, a contribution from the Atlantic Forest biodiversity for the production of vanilla: A proteomic approach through high-definition nanoLC/MS

Only a few cultivated species of Vanilla are used to produce vanilla, despite the high demand, predatory exploitation, and low genetic variability that threaten the production of natural vanilla. Vanilla bahiana pods from the Atlantic Forest may be an alternative source of natural vanilla. This study applied bottom-up and shotgun proteomics analysis to identify proteins related to flowering, fruiting, and vanilla-flavor production. Extraction solutions, including Tris-HCl buffer, β-mercaptoethanol and SDS, were assayed. SDS proved to be feasible for extraction of Vanilla fruit proteins and could be an alternative to the phenol method of protein extraction. Progenesis QI for Proteomics (QIP) software loaded with an Orchidaceae database identified 2326 proteins in our samples. Among these, 75 were highlighted as useful for the synthesis of compounds related to vanilla flavor, such as vanillin synthase, which was successfully extracted with 1% SDS, which also improved the variety of the extracted proteins. The proteins identified in V. bahiana pods indicate the enzymatic potential of this species, as further validated by quantifying the vanilla in the samples.

Single-repeat R3 MYB transcription factors from Platanus acerifolia negatively regulate trichome formation in Arabidopsis

Four R3 MYB genes were cloned and identified from Platanus acerifolia and analysed according to endogenous gene expression profiles, protein-protein interaction patterns, phenotypic effects and related gene expression profiles in transgenic Arabidopsis, suggesting that London plane R3 MYB genes inhibit trichome formation in Arabidopsis. The CPC-like MYB transcription factors including CAPRICE (CPC), TRIPTYCHON (TRY), ENHANCER OF TRY AND CPC 1, 2 and 3 (ETC1, ETC2 and ETC3), TRICHOMELESS1 (TCL1) and TRICHOMELESS2(TCL2) play important roles in controlling trichome patterning in Arabidopsis. In this study, four sequences homologous with the Arabidopsis CPC family were identified from London plane and named PaTRY, PaCPC-like1, PaCPC-like2 and PaCPC-like3. Over-expression of PaTRY, PaCPC-like1, PaCPC-like2 and PaCPC-like3 in Arabidopsis resulted in glabrous phenotypes. In addition, expression of endogenous GL2, GL1, MYB23, TTG2 and a set of R3 MYB-encoding genes was markedly reduced. Furthermore, the protein products of PaTRY, PaCPC-like1, PaCPC-like2 and PaCPC-like3 were shown to interact with PaGL3 in yeast two-hybrid assays. Together, these results likely suggest that the mechanisms of trichome regulation in London plane have similarities with those in Arabidopsis.

Identification and characterization of FRUITFULL-like genes from Platanus acerifolia, a basal eudicot tree

The function of euAP1 and euFUL in AP1/FUL lineage have been well characterized in core eudicots, and they play common and distinct roles in plant development. However, the evolution and function of FUL-like genes is poorly understood in basal eudicots. In this study, we identified three FUL-like genes PlacFL1/2/3 from London plane (Platanus acerifolia). Sequence alignment and phylogenetic analysis indicated that PlacFL1/2/3 are AP1/FUL orthologs and encoded proteins containing FUL motif and paleoAP1 motif. Quantitative real-time PCR (qRT-PCR) analysis showed that PlacFL1/2/3 were expressed in both vegetative and reproductive tissues, but with distinct spatiotemporal patterns. In contrast to PlacFL1 and PlacFL3, PlacFL2 exhibited higher expression levels and broader expression regions, and that the expression of PlacFL2 gene showed a decreasing and increasing tendency in subpetiolar buds during dormancy induction and breaking, respectively. Overexpression of PlacFLs in Arabidopsis and PlacFL3 in tobacco resulted in early flowering, as well as early termination of inflorescence meristems for transgenic Arabidopsis plants. The expression changes of flowering time and flower meristem identity genes in transgenic Arabidopsis lines with different PlacFLs suggested that PlacFL2 and PlacFL3 may regulate different downstream genes to perform divergent functions. Yeast two-hybrid analysis indicated that PlacFLs interacted strongly with PlacSEP proteins, and PlacFL3 instead of PlacFL1 and PlacFL2 could also form a homodimer and interact with D-class proteins. Our results suggest that PlacFLs may play conserved functions in regulating flowering and flower development, and PlacFL2 might also be involved in dormancy regulation. The research helps us to understand the functional evolution of FUL-like genes in basal eudicots, especially in perennial woody species.

Functional conservation and divergence of five SEPALLATA-like genes from a basal eudicot tree, Platanus acerifolia

MAIN CONCLUSION

Five SEP -like genes were cloned and identified from Platanus acerifolia through the analysis of expression profiles, protein-protein interaction patterns, and transgenic phenotypes, which suggested that they play conservative and diverse functions in floral initiation and development, fruit development, bud growth, and dormancy. SEPALLATA (SEP) genes have been well characterized in core eudicots and some monocots, and they play important and diverse roles in plant development, including flower meristem initiation, floral organ identity, and fruit development and ripening. However, the knowledge on the function and evolution of SEP-like genes in basal eudicot species is very limited. Here, we cloned and identified five SEP-like genes from London plane (Platanus acerifolia), a basal eudicot tree that is widely used for landscaping in cities. Sequence alignment and phylogenetic analysis indicated that three genes (PlacSEP1.1, PlacSEP1.2, and PlacSEP1.3) belong to the SEP1/2/4 clade, while the other two genes (PlacSEP3.1 and PlacSEP3.2) are grouped into the SEP3 clade. Quantitative real-time PCR (qRT-PCR) analysis showed that all PlacSEPs, except PlacSEP1.1 and PlacSEP1.2, were expressed during the male and female inflorescence initiation, and throughout the flower and fruit development process. PlacSEP1.2 gene expression was only detected clearly in female inflorescence at April. PlacSEP1.3 and PlacSEP3.1 were also expressed, although relatively weak, in vegetative buds of adult trees. No evident PlacSEPs transcripts were detected in various organs of juvenile trees. Overexpression of PlacSEPs in Arabidopsis and tobacco plants resulted in different phenotypic alterations. 35S:PlacSEP1.1, 35S:PlacSEP1.3, and 35S:PlacSEP3.2 transgenic Arabidopsis plants showed evident early flowering, with less rosette leaves but more cauline leaves, while 35S:PlacSEP1.2 and PlacSEP3.1 transgenic plants showed no visible phenotypic changes. 35S:PlacSEP1.1 and 35S:PlacSEP3.2 transgenic Arabidopsis plants also produced smaller and curled leaves. Overexpression of PlacSEP1.1 and PlacSEP3.1 in tobacco resulted in the early flowering and producing more lateral branches. Yeast two-hybrid analysis indicated that PlacSEPs proteins can form homo- or hetero-dimers with the Platanus APETALA1 (AP1)/FRUITFULL (FUL), B-, C-, and D-class MADS-box proteins in different interacting patterns and intensities. Our results suggest that the five PlacSEP genes may play important and divergent roles during floral initiation and development, as well as fruit development, by collaborating with FUL, B-, C-, and D-class MADS-box genes in London plane; PlacSEP1.3 and PlacSEP3.1 genes might also involve in vegetative bud growth and dormancy. The results provide valuable data for us to understand the functional evolution of SEP-like genes in basal eudicot species.

Detoxification strategies and regulation of oxygen production and flowering of Platanus acerifolia under lead (Pb) stress by transcriptome analysis

Toxic metal pollution is a major environmental problem that has received wide attention. Platanus acerifolia (London plane tree) is an important greening tree species that can adapt to environmental pollution. The genetic basis and molecular mechanisms associated with the ability of P. acerifolia to respond lead (Pb) stress have not been reported so far. In this study, 16,246 unigenes differentially expressed unigenes that were obtained from P. acerifolia under Pb stress using next-generation sequencing. Essential pathways such as photosynthesis, and gibberellins and glutathione metabolism were enriched among the differentially expressed unigenes. Furthermore, many important unigenes, including antioxidant enzymes, plants chelate compounds, and metal transporters involved in defense and detoxification mechanisms, were differentially expressed in response to Pb stress. The unigenes encoding the oxygen-evolving enhancer Psb and OEE protein families were downregulated in Pb-stressed plants, implying that oxygen production might decrease in plants under Pb stress. The relationship between gibberellin and P. acerifolia flowering is also discussed. The information and new insights obtained in this study will contribute to further investigations into the molecular regulation mechanisms of Pb accumulation and tolerance in greening tree species.