Mechanical superiority of Pseudoxytenanthera bamboo for sustainable engineering solutions.

The advancement in natural fibre composites has replaced synthetic fibres in various commercial sectors. Bamboo species possess high mechanical properties due to their lignocellulosic fibre content, which makes them suitable for engineering applications and potential alternatives to solid wood. However, despite Bamboo being composed of 130 genera and 1700 different species, out of which many still remains underexplored. In this study, we investigated the, Lignocellulosic profiling, fibre strength, and mechanical characterization of two species of Pseudoxytenanthera Bamboo: Pseudoxytenanthera ritchiei, Pseudopxytenanthera stocksii, and the results obtained were compared with Bambusa balcooa, one of the priority species of bamboo identified by The International Plant Genetic Resources Institute (IPGRI). BET (Brunauer-Emmett-Teller) was used to quantify the samples' density, while SEM-EDX and FTIR spectroscopy were used for elemental analysis. The samples were then subjected to tensile test in addition, thermogravimetric analysis and water absorption test were carried out for the three species. The results showed that Pseudoxytenanthera species possessed superior chemical and mechanical characteristics compared to the priority species of bamboo used for composites. Out of the two Pseudoxytenanthera species studied, Pseudoxytenanthera stocksii exhibited the highest values of cellulose, hemicellulose, lignin, pectin, ash, carbon, and silicon, indicating its chemical superiority. Moreover, Pseudoxytenanthera stocksii also showed higher mechanical values for tensile strength, making it suitable for a variety of engineering applications. The TGA values also indicated that Pseudoxytenanthera stocksii is stable at high temperatures when compared with other natural fibres.

Bambusa vulgaris leaves reverse mitochondria dysfunction in diabetic rats through modulation of mitochondria biogenic genes.

OBJECTIVES: There is evidence that mitochondrial dysfunction mediated by hyperglycemia increases the incidence of diabetes and age-related insulin resistance. Thus, maintaining mitochondrial integrity may provide alternative therapeutic approach in diabetes treatment. This study aimed to evaluate the effect of Bambusa vulgaris leaf extract on mitochondrial biogenesis in the pancreas of diabetic rats. METHODS: 11 weeks old male rats (n=30) were purchased, and sorted into the following groups: control, diabetic control, diabetes + metformin (100 mg/kg), diabetes + Aq. B. vulgaris (100 mg/kg), diabetes + Aq. B. vulgaris (200 mg/kg), and diabetes + Aq. B. vulgaris (300 mg/kg). Diabetes was induced in the rats by a single dose of 65 mg/kg streptozotocin (STZ). The mRNA expression of genes related to mitochondria biogenesis (pgc-1α, Nrf2, GSK3ß, AMPK and SIRT2) and genes of Nrf2-Keap1-ARE signaling pathway were determined by reverse transcriptase polymerase chain reaction. Molecular docking studies including lock and key docking and prime MM-GBSA were incorporated to identify the lead chemical compounds in Bambusa vulgari. RESULTS: The results showed that B. vulgaris leaf extract promotes mitochondrial biogenesis via altering the mRNA expression of mitochondrial master regulator pgc-1α, other upstream genes, and the Nrf2-Keap1-ARE antioxidant pathway. Through molecular docking results, cryptochlorogenic acid, hesperidin, orientin, vitexin, scopolin, and neochlorogenic were found as the crucial chemicals in B. vulgaris with the most modulating effect on PGC-1α, AMPK, and GSK3. CONCLUSIONS: This study thus suggests that B. vulgaris leaf extract restores the integrity of mitochondria in diabetic rats.

Functional Identification of Arthrinium phaeospermum Effectors Related to Bambusa pervariabilis × Dendrocalamopsis grandis Shoot Blight.

The shoot blight of Bambusa pervariabilis × Dendrocalamopsis grandis caused by Arthrinium phaeospermum made bamboo die in a large area, resulting in serious ecological and economic losses. Dual RNA-seq was used to sequence and analyze the transcriptome data of A. phaeospermum and B. pervariabilis × D. grandis in the four periods after the pathogen infected the host and to screen the candidate effectors of the pathogen related to the infection. After the identification of the effectors by the tobacco transient expression system, the functions of these effectors were verified by gene knockout. Fifty-three differentially expressed candidate effectors were obtained by differential gene expression analysis and effector prediction. Among them, the effectors ApCE12 and ApCE22 can cause programmed cell death in tobacco. The disease index of B. pervariabilis × D. grandis inoculated with mutant ΔApCE12 and mutant ΔApCE22 strains were 52.5% and 47.5%, respectively, which was significantly lower than that of the wild-type strains (80%), the ApCE12 complementary strain (77.5%), and the ApCE22 complementary strain (75%). The tolerance of the mutant ΔApCE12 and mutant ΔApCE22 strains to H2O2 and NaCl stress was significantly lower than that of the wild-type strain and the ApCE12 complementary and ApCE22 complementary strains, but there was no difference in their tolerance to Congo red. Therefore, this study shows that the effectors ApCE12 and ApCE22 play an important role in A. phaeospermum virulence and response to H2O2 and NaCl stress.

Exploring phylogenetic relationships within the subgenera of Bambusa based on DNA barcodes and morphological characteristics.

The genus Bambusa belongs to the subtribe Bambusinae and the subfamily Bambusoideae. The subgenera of Bambusa has not been satisfactorily circumscribed, and this remains a major taxonomic issue. Simultaneously, genera such as Dendrocalamus and Gigantochloa have not been confidently assigned to Bambusa. Here, the phylogenetic relationships among subgenera were investigated using five chloroplast DNA markers (rpl32-trnL, rpl16, matK, rbcL, and trnH-psbA) for a sample of 50 ingroup and 16 outgroup species. A total of 186 key morphological descriptors were studied for the 50 ingroup species. The results indicated that five chloroplast DNA markers were possible to distinguish Bambusa species from other species and divide them into several clusters. Phylogenetic analyses conducted using morphological descriptors and a combined marker (rpl32-trnL+rpl16) revealed three and five distinct lineages, respectively, among the currently recognized Bambusa species. The branching pattern of the dendrogram was not completely consistent with the classical taxonomic classification of Bambusa. In addition, not all varieties and cultivars were clustered with McClure classifications. As the maximum parsimony topology and morphological analyses were inconsistent, some clustering results overlapped. Overall, the results obtained here do not support the current classification of the Bambusa subgenera.

A comprehensive analysis of the floral transition in ma bamboo (Dendrocalamus latiflorus) reveals the roles of DlFTs involved in flowering.

Bamboo has a unique flowering characteristics of long and unpredictable vegetative period, which differs from annual herbs and perennial woody plants. In order to understand the molecular regulatory mechanism of bamboo flowering, a comprehensive study was conducted in ma bamboo (Dendrocalamus latiflorus Munro), including morphological, physiological and transcriptiome analyses. Differentially expressed genes related to the flowering pathway were identified by comparative transcriptome analysis. DlFT1, a homologous gene of FT/Hd3a, was significantly upregulated in flowering bamboo. Direct differentiation of spikelets from calli occurred and the downstream gene AP1 was upregulated in the transgenic bamboo overexpressing DlFT1. Transgenic rice overexpressing DlFT1 showed a strong early flowering phenotype. DlFT1 and DlTFL1 could interact with DlFD, and DlTFL1 delayed flowering. It is presumed that DlTFL1 plays an antagonistic role with DlFT1 in ma bamboo. In addition, the expression of DlFT1 was regulated by DlCO1, indicating that a CO-FT regulatory module might exist in ma bamboo. These results suggest that DlFT1 is a florigen candidate gene with conservative function in promoting flowering. Interestingly, the results have shown for the first time that DlFT2 can specifically interact with E3 ubiquitin ligase WAV3, while DlFT3 transcripts are mainly nonsense splicing. These findings provide better understanding of the roles of the florigen gene in bamboo and lay a theoretical basis for regulating bamboo flowering in the future.

First Report of Distinct Bamboo mosaic virus (BaMV) Isolates Infecting Bambusa funghomii in Vietnam and the Identification of a Highly Variable Region in the BaMV Genome.

New isolates of the Bamboo mosaic virus (BaMV) were identified in Bambusa funghomii bamboo in Vietnam. Sequence analyses revealed that the Vietnam isolates are distinct from all known BaMV strains, sharing the highest sequence identities (about 77%) with the Yoshi isolates reported in California, USA. Unique satellite RNAs were also found to be associated with the BaMV Vietnam isolates. A possible recombination event was detected in the genome of BaMV-VN2. A highly variable region was identified in the ORF1 gene, in between the methyl transferase domain and helicase domain. These results revealed the presence of unique BaMV isolates in an additional bamboo species in one more country, Vietnam, and provided evidence in support of the possible involvement of environmental or host factors in the diversification and evolution of BaMV.

RNA-seq and phytohormone analysis reveals the culm color variation of Bambusa oldhamii Munro.

BACKGROUND: The clumping bamboo Bambusa oldhamii Munro, known as "green bamboo", is famous for its edible bamboo shoots and fast-growing timber. The green and yellow striped-culm B. oldhamii variety, named B. oldhamii f. revoluta W.T. Lin & J. Y. Lin, is an attractive system for researching the culm color variation of B. oldhamii. METHODS: Millions of clean reads were generated and assembled into 604,900 transcripts, and 383,278 unigenes were acquired with RNA-seq technology. The quantification of ABA, IAA, JA, GA1, GA3, GA4, and GA7 was performed using HPLC-MS/MS platforms. RESULTS: Differential expression analysis showed that 449 unigenes were differentially expressed genes (DEGs), among which 190 DEGs were downregulated and 259 DEGs were upregulated in B. oldhamii f. revoluta. Phytohormone contents, especially GA1 and GA7, were higher in B. oldhamii. Approximately 21 transcription factors (TFs) were differentially expressed between the two groups: the bZIP, MYB, and NF-YA transcription factor families had the most DEGs, indicating that those TFs play important roles in B. oldhamii culm color variation. RNA-seq data were confirmed by quantitative RT-PCR analysis of the selected genes; moreover, phytohormone contents, especially those of ABA, GA1 and GA7, were differentially accumulated between the groups. Our study provides a basal gene expression and phytohormone analysis of B. oldhamii culm color variation, which could provide a solid fundamental theory for investigating bamboo culm color variation.

The transcriptional dynamics during de novo shoot organogenesis of Ma bamboo (Dendrocalamus latiflorus Munro): implication of the contributions of the abiotic stress response in this process.

De novo shoot organogenesis is an important biotechnological tool for fundamental studies in plant. However, it is difficult in most bamboo species, and the genetic control of this highly dynamic and complicated regeneration process remains unclear. In this study, based on an in-depth analysis at the cellular level, the shoot organogenesis from calli of Ma bamboo (Dendrocalamus latiflorus Munro) was divided into five stages. Subsequently, single-molecule long-read isoform sequencing of tissue samples pooled from all five stages was performed to generate a full-length transcript landscape. A total of 83 971 transcripts, including 73 209 high-quality full-length transcripts, were captured, which served as an annotation reference for the subsequent RNA sequencing analysis. Time-course transcriptome analysis of samples at the abovementioned five stages was conducted to investigate the global gene expression atlas showing genome-wide expression of transcripts during the course of bamboo shoot organogenesis. K-means clustering analysis and stage-specific transcript identification revealed important dynamically expressed transcription regulators that function in bamboo shoot organogenesis. The majority of abiotic stress-responsive genes altered their expression levels during this process, and further experiments demonstrated that exogenous application of moderate but not severe abiotic stress increased the shoot regeneration efficiency. In summary, our study provides an overview of the genetic flow dynamics during bamboo shoot organogenesis. Full-length cDNA sequences generated in this study can serve as a valuable resource for fundamental and applied research in bamboo in the future.

Silica and secondary metabolites as chemophenetic markers for characterization of bamboo species in relation to genetic and morphometric analysis.

Bamboo is a non-timber forest product and one of the most important grass plants of industrial and domestic use. It is widely distributed in tropical countries including India, China and Southeast Asian countries with wide genetic diversity. The diversity in the available genotypes becomes an important resource for the selection and improvement of the plants for ecological and commercial use. This study investigates eight commercially and ecologically important bamboo species of six genera (Bambusa, Dendrocalamus, Thyrsostachys, Vietnamosasa, Cephalostachyum and Indocalamus) from India, Thailand and Laos. These were evaluated for genetic differences by molecular makers, chemo-morphological variation and ability of silicon accumulation. The genetic cluster analyses of eight RAPD primers revealed genetic similarities in the ranges of 24-55%. The total silica content varied from 18.34 to 40.08 ppm in leaves of different bamboo species. Chemical analysis of the silicon content by ICP-OES and secondary metabolite profiling on TLC depicted the prominent distinction among the species. The PCA analysis of quantitative morphological data grouped the species in two major clusters and found to correlate with chemical pattern and genetic similarity to some extent. This is the first report that summarizes species-specific variability of leaf silica content, secondary metabolites, and quantitative morphological data towards delineation of genetic phylogeny of bamboo species.

Traditional System Versus DNA Barcoding in Identification of Bamboo Species: A Systematic Review.

Bamboo, a gramineous plant belonging to the family Poaceae, comprises of 1575 species from 116 genera across the globe. It has the ability to grow and evolve on degraded land and hence, can be utilized in the various applications as an alternative for plastic and wood. DNA barcoding, a long genomic sequence, identifies barcode region which shows species-specific nucleotide differences. This technology is considered as advanced molecular technique utilized for characterization and classification of the various species by applying distinctive molecular markers. Recent investigations revealed the potential application of various barcode regions such as matK, rbcL, rpoB, rpoC1, psbA-trnH, and ITS2, in identification of many bamboo species from different genus. In this review we comprehensively discussed the relevance of DNA barcoding as a tool in classification/identification of various bamboo species. We highlighted the methodology, how this advance technology overcomes the challenges associated with traditional methods along with prospects for future research.

Identification and functional characterization of two bamboo FD gene homologs having contrasting effects on shoot growth and flowering.

Bamboos, member of the family Poaceae, represent many interesting features with respect to their fast and extended vegetative growth, unusual, yet divergent flowering time across species, and impact of sudden, large scale flowering on forest ecology. However, not many studies have been conducted at the molecular level to characterize important genes that regulate vegetative and flowering habit in bamboo. In this study, two bamboo FD genes, BtFD1 and BtFD2, which are members of the florigen activation complex (FAC) have been identified by sequence and phylogenetic analyses. Sequence comparisons identified one important amino acid, which was located in the DNA-binding basic region and was altered between BtFD1 and BtFD2 (Ala146 of BtFD1 vs. Leu100 of BtFD2). Electrophoretic mobility shift assay revealed that this alteration had resulted into ten times higher binding efficiency of BtFD1 than BtFD2 to its target ACGT motif present at the promoter of the APETALA1 gene. Expression analyses in different tissues and seasons indicated the involvement of BtFD1 in flower and vegetative development, while BtFD2 was very lowly expressed throughout all the tissues and conditions studied. Finally, a tenfold increase of the AtAP1 transcript level by p35S::BtFD1 Arabidopsis plants compared to wild type confirms a positively regulatory role of BtFD1 towards flowering. However, constitutive expression of BtFD1 had led to dwarfisms and apparent reduction in the length of flowering stalk and numbers of flowers/plant, whereas no visible phenotype was observed for BtFD2 overexpression. This signifies that timely expression of BtFD1 may be critical to perform its programmed developmental role in planta.

Cloning and characterization of the Bambusa oldhamii BoMDH-encoded malate dehydrogenase.

Malate dehydrogenase (MDH), which is ubiquitously occurred in nature, catalyzes the interconversion of malate and oxaloacetate. Higher plants contain multiple forms of MDH that differ in coenzyme specificity, subcellular localization and physiological function. A putative Bambusa oldhamii BoMDH cDNA was screened with the specific probe from the bamboo cDNA library. Sequence alignment shows that there's a high homology between the deduced amino acid sequence of BoMDH and MDH protein in Oryza sativa glyoxysome (92%). A 57 kDa fusion protein was expressed by IPTG induction in Escherichia coli BL21 (DE3), and an obvious MDH activity was detected in the recombinant protein. The molecular mass of recombinant BoMDH was estimated to be 120 kDa, and the subunit form was 57 kDa by denatured SDS-PAGE, indicating that BoMDH presents as a homodimer. The optimum temperature and pH for BoMDH activity were 40 °C and 9.5, respectively. The Km values of BoMDH for malate and NAD+ were 5.2 mM and 0.52 mM. The kcat/Km values of BoMDH for malate and NAD+ were 163 min-1 mM-1 and 3060 min-1 mM-1.

Bioproduction of glucose conjugates of 4-hydroxybenzoic and vanillic acids using bamboo cells transformed to express bacterial 4-hydroxycinnamoyl-CoA hydratase/lyase.

Rational metabolic-flow switching, which we proposed recently, is an effective strategy to produce an exogenous high-value natural product using transformed plant cells; the proof of this concept was demonstrated using bamboo (Phyllostachys nigra; Pn) cells as a model system. Pn cells were transformed to express 4-hydroxycinnamoyl-CoA hydratase/lyase of Pseudomonas putida KT2440 (PpHCHL), which catalyzes the formation of 4-hydroxybenzaldehyde and vanillin from p-coumaroyl-CoA and feruloyl-CoA, respectively. The PpHCHL-transformed cells accumulated glucose conjugates of 4-hydroxybenzoic acid and vanillic acid, indicating that the PpHCHL products (aldehydes) were further metabolized by inherent enzymes in the Pn cells. The production titers of 4-hydroxybenzoic acid glucose ester, vanillic acid glucose ester, and 4-hydroxybenzoic acid glucoside reached 1.7, 0.17, and 0.14 g/L at the maximum, respectively. These results proved the versatility of Pn cells for producing vanillin-related compounds based on rational metabolic-flow switching.

ddRAD analyses reveal a credible phylogenetic relationship of the four main genera of Bambusa-Dendrocalamus-Gigantochloa complex (Poaceae: Bambusoideae).

The Bambusa-Dendrocalamus-Gigantochloa complex (BDG complex) is the most diversified and phylogenetically recalcitrant group of the paleotropical woody bamboos. Species of this complex occur in tropical and subtropical Asia and most of them are of great economic, cultural and ecological value. The lack of resolution achieved through the analyses of previous molecular datasets has long confounded its phylogenetic estimation and generic delimitation. Here, we adopted a ddRAD-seq strategy to investigate phylogenetic relationships of the four main genera (Bambusa, Dendrocalamus, Gigantochloa, and Melocalamus) in the BDG complex. A total of 102 species were sampled, and SNP data were generated. Both MP and ML analyses of the ddRAD-seq data resulted in a well-resolved topology with Gigantochloa and Melocalamus confirmed as monophyletic, and Melocalamus resolved as sister to the rest of the complex. Bambusa and Dendrocalamus were both resolved as paraphyletic. The phylogenetic relationships were mostly supported by morphological evidence including characters of the branch complement, rachilla, lodicules, filaments and stigma. We also generated and assembled complete plastid genomes of 48 representative species. There were conflicts between the plastome and the ddRAD topologies. Our study demonstrated that RAD-seq can be used to reconstruct evolutionary history of lineages such as the bamboos where ancient hybridization and polyploidy play a significant role. The four genera of the BDG complex have a complex evolutionary history which is likely a product of ancient introgression events.

Comparative transcriptome analysis of Bambusa pervariabilis × Dendrocalamopsis grandis against Arthrinium phaeospermum under protein AP-toxin induction.

Bambusapervariabilis × Dendrocalamopsisgrandis, a fast-growing and easily propagated bamboo species, has been extensively planted in the southern China, resulting in huge ecological benefits. In recent years, it was found that the pathogenic fungus Arthrinium phaeospermum caused the death of a large amount of bamboo. In this study, the transcriptome of B. pervariabilis × D. grandis, induced by inactivated protein AP-toxin from A. phaeospermum was sequenced and analyzed, to reveal the resistance mechanism induced by biotic agents of B. pervariabilis × D. grandis against A. phaeospermum at the gene level. Transcriptome sequencing was performed by Illumina HiSeq 2000 in order to analyze the differentially expressed genes (DEGs) of B. pervariabilis × D. grandis in response to different treatment conditions. In total, 201,875,606 clean reads were obtained, and the percentage of Q30 bases in each sample was more than 94.21%. There were 6398 DEGs in the D-J group (inoculation with a pathogenic spore suspension after three days of AP-toxin induction) compared to the S-J group (inoculation with a pathogenic spore suspension after inoculation of sterile water for three days) with 3297 up-regulated and 3101 down-regulated genes. For the D-S group (inoculation with sterile water after inoculation of AP-toxin for three days), there were 2032 DEGs in comparison to the S-S group (inoculation with sterile water only), with 1035 up-regulated genes and 997 down-regulated genes. These identified genes were mainly involved in lignin and phytoprotein synthesis, tetrapyrrole synthesis, redox reactions, photosynthesis, and other processes. The fluorescence quantitative results showed that 22 pairs of primer amplification products were up-regulated and 7 were down-regulated. The rate of similarity between these results and the sequencing results of the transcription group was 100%, which confirmed the authenticity of the transcriptome sequencing results. Redox proteins, phenylalanine ammonia lyase, and S-adenosine-L-methionine synthetase, among others, were highly expressed; these results may indicate the level of disease resistance of the bamboo. These results provide a foundation for the further exploration of resistance genes and their functions.

Differential Proteome Analysis of Hybrid Bamboo (Bambusa pervariabilis × Dendrocalamopsis grandis) Under Fungal Stress (Arthrinium phaeospermum).

In this study, TMT (tandem mass tag)-labeled quantitative protein technology combined with LC-MS/MS (liquid chromatography-mass spectrometry/mass spectrometry) was used to isolate and identify the proteins of the hybrid bamboo (Bambusa pervariabilis × Dendrocalamopsis grandis) and the bamboo inoculated with the pathogenic fungi Arthrinium phaeospermum. A total of 3320 unique peptide fragments were identified after inoculation with either A. phaeospermum or sterile water, and 1791 proteins were quantified. A total of 102 differentially expressed proteins were obtained, of which 66 differential proteins were upregulated and 36 downregulated in the treatment group. Annotation and enrichment analysis of these peptides and proteins using the GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) databases with bioinformatics software showed that the differentially expressed protein functional annotation items were mainly concentrated on biological processes and cell components. The LC-PRM/MS (liquid chromatography-parallel reaction monitoring/mass spectrometry) quantitative analysis technique was used to quantitatively analyze 11 differential candidate proteins obtained by TMT combined with LC-MS/MS. The up-down trend of 10 differential proteins in the PRM results was consistent with that of the TMT quantitative analysis. The coincidence rate of the two results was 91%, which confirmed the reliability of the proteomic results. Therefore, the differentially expressed proteins and signaling pathways discovered here may be the further concern for the bamboo-pathogen interaction studies.

Molecular characterization and expression pattern analysis of a novel stress-responsive gene 'BeSNAC1' in Bambusa emeiensis.

NAC transcription factors (TFs) are master regulators of environmental stresses exerting a crucial role in plant growth and development. However, the studies on NAC TFs from Bambusa emeiensis are scarce. In this investigation, a novel gene from B. emeiensis encoding NAC protein was cloned and characterized. The gene was isolated based on the amino acid sequence data of stress-responsive SNAC1 of rice, named 'BeSNAC1 (accession no. MG763922)'. The full-length sequence of 1681 bp was found to contain an open-reading frame of 912 bp that encode a protein of 303 amino-acid residues. The multiple protein sequence alignments unveiled that BeSNAC1 contains a typical NAC domain. Additionally, the phylogenetic analysis showed that the corresponding protein belonged to the SNAC group, as it cladded with SNAC1, HvSNAC1, TaNAC2, SbSNAC1 and ZmSNAC1 proteins. Transactivation and subcellular localization assay disclosed that BeSNAC1 is a transcriptional activator localized in the cell nucleus.Moreover, the time-dependent expression pattern of BeSNAC1 was profiled under abscisic acid (ABA), polyethylene glycol 6000 (PEG-6000), NaCl, H2O2 and Na2SO4 treatments via a quantitative real-time polymerase chain reaction. The results revealed that the expression of BeSNAC1 was significantly upregulated in all treatments, a significant difference was observed under H2O2, NaCland ABA (P 0.001) and PEG and Na2SO4 (P < 0.01) treatments, respectively. Conclusively, our findings provide evidence that 'BeSNAC1' is a nuclear protein that might act as part of the transcription regulation complex and is involved in the ABA signalling pathway and abiotic stress tolerance mechanisms in B. emeiensis.

Overexpression of PvCO1, a bamboo CONSTANS-LIKE gene, delays flowering by reducing expression of the FT gene in transgenic Arabidopsis.

BACKGROUND: In Arabidopsis, a long day flowering plant, CONSTANS (CO) acts as a transcriptional activator of flowering under long day (LD) condition. In rice, a short day flowering plant, Hd1, the ortholog of CO, plays dual functions in respond to day-length, activates flowering in short days and represses flowering in long days. In addition, alleles of Hd1 account for ~ 44% of the variation in flowering time observed in cultivated rice and sorghum. How does it work in bamboo? The function of CO in bamboo is similar to that in Arabidopsis? RESULTS: Two CO homologous genes, PvCO1 and PvCO2, in Phyllostachys violascens were identified. Alignment analysis showed that the two PvCOLs had the highest sequence similarity to rice Hd1. Both PvCO1 and PvCO2 expressed in specific tissues, mainly in leaf. The PvCO1 gene had low expression before flowering, high expression during the flowering stage, and then declined to low expression again after flowering. In contrast, expression of PvCO2 was low during the flowering stage, but rapidly increased to a high level after flowering. The mRNA levels of both PvCOs exhibited a diurnal rhythm. Both PvCO1 and PvCO2 proteins were localized in nucleus of cells. PvCO1 could interact with PvGF14c protein which belonged to 14-3-3 gene family through B-box domain. Overexpression of PvCO1 in Arabidopsis significantly caused late flowering by reducing the expression of AtFT, whereas, transgenic plants overexpressing PvCO2 showed a similar flowering time with WT under LD conditions. Taken together, these results suggested that PvCO1 was involved in the flowering regulation, and PvCO2 may either not have a role in regulating flowering or act redundantly with other flowering regulators in Arabidopsis. Our data also indicated regulatory divergence between PvCOLs in Ph. violascens and CO in Arabidopsis as well as Hd1 in Oryza sativa. Our results will provide useful information for elucidating the regulatory mechanism of COLs involved in the flowering. CONCLUSIONS: Unlike to the CO gene in Arabidopsis, PvCO1 was a negative regulator of flowering in transgenic Arabidopsis under LD condition. It was likely that long period of vegetative growth of this bamboo species was related with the regulation of PvCO1.

Identification, characterization and gene expression analyses of important flowering genes related to photoperiodic pathway in bamboo.

BACKGROUND: Bamboo is an important member of the family Poaceae and has many inflorescence and flowering features rarely observed in other plant groups. It retains an unusual form of perennialism by having a long vegetative phase that can extend up to 120 years, followed by flowering and death of the plants. In contrast to a large number of studies conducted on the annual, reference plants Arabidopsis thaliana and rice, molecular studies to characterize flowering pathways in perennial bamboo are lacking. Since photoperiod plays a crucial role in flower induction in most plants, important genes involved in this pathway have been studied in the field grown Bambusa tulda, which flowers after 40-50 years. RESULTS: We identified several genes from B. tulda, including four related to the circadian clock [LATE ELONGATED HYPOCOTYL (LHY), TIMING OF CAB EXPRESSION1 (TOC1), ZEITLUPE (ZTL) and GIGANTEA (GI)], two circadian clock response integrators [CONSTANS A (COA), CONSTANS B (COB)] and four floral pathway integrators [FLOWERING LOCUS T1, 2, 3, 4 (FT1, 2, 3, 4)]. These genes were amplified from either gDNA and/or cDNA using degenerate as well as gene specific primers based on homologous sequences obtained from related monocot species. The sequence identity and phylogenetic comparisons revealed their close relationships to homologs identified in the temperate bamboo Phyllostachys edulis. While the four BtFT homologs were highly similar to each other, BtCOA possessed a full-length B-box domain that was truncated in BtCOB. Analysis of the spatial expression of these genes in selected flowering and non-flowering tissue stages indicated their possible involvement in flowering. The diurnal expression patterns of the clock genes were comparable to their homologs in rice, except for BtZTL. Among multiple BtCO and BtFT homologs, the diurnal pattern of only BtCOA and BtFT3, 4 were synchronized in the flower inductive tissue, but not in the non-flowering tissues. CONCLUSION: This study elucidates the photoperiodic regulation of bamboo homologs of important flowering genes. The finding also identifies copy number expansion and gene expression divergence of CO and FT in bamboo. Further studies are required to understand their functional role in bamboo flowering.

Transcriptome analysis provides insights into xylogenesis formation in Moso bamboo (Phyllostachys edulis) shoot.

Maturation-related changes in cell wall composition and the molecular mechanisms underlying cell wall changes were investigated from the apical, middle and basal segments in moso bamboo shoot (MBS). With maturation extent from apical to basal regions in MBS, lignin and cellulose content increased, whereas heteroxylan exhibited a decreasing trend. Activities of phenylalanine amonnialyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and cinnamate-4-hydroxylase (C4H), which are involved in lignin biosynthesis, increased rapidly from the apex to the base sections. The comparative transcriptomic analysis was carried out to identify some key genes involved in secondary cell walls (SCW) formation underlying the cell wall compositions changes including 63, 8, 18, and 31 functional unigenes encoding biosynthesis of lignin, cellulose, xylan and NAC-MYB-based transcription factors, respectively. Genes related to secondary cell wall formation and lignin biosynthesis had higher expression levels in the middle and basal segments compared to those in the apical segments. Furthermore, the expression profile of PePAL gene showed positive relationships with cellulose-related gene PeCESA4, xylan-related genes PeIRX9 and PeIRX10. Our results indicated that lignification occurred in the more mature middle and basal segments in MBS at harvest while lignification of MBS were correlated with higher expression levels of PeCESA4, PeIRX9 and PeIRX10 genes.