Genome-wide characterization of the biggest grass, bamboo, based on 10,608 putative full-length cDNA sequences

Mitochondrial Energy Homeostasis and Membrane Interaction Regulate the Rapid Growth of Moso Bamboo

The rapid growth of moso bamboo is primarily attributed to the swift elongation of its internodes. While mitochondria are known to provide energy for various cellular processes, the specific mechanisms by which they facilitate rapid growth in bamboo remain elusive. In this study, we optimised the procedures for mitochondria isolation and performed a comprehensive analysis of mitochondrial dynamics and proteomics from internodes at various growth stages, including the initial growth (IG) stage, the starting of cell division (SD), and the rapid elongation (RE). Confocal observation demonstrated that cells in the RE stage have a higher mitochondrial density and increased mitochondrial motility compared to other stages. Proteomic analysis of isolated mitochondria revealed an upregulation of the tricarboxylic acid cycle, along with a synchronous increase in both mitochondrial- and nuclear-encoded components of oxidative phosphorylation in RE cells. Moreover, the upregulation of various mitochondrial membrane transporters in RE cells suggests an enhanced exchange of metabolic intermediates and inorganic ions with the cytosol. Intriguingly, ultrastructural analysis and pharmacological treatments revealed membrane interactions between the endoplasmic reticulum (ER) and mitochondria in RE cells. In conclusion, our study provides novel insights into mitochondrial function and the intracellular dynamics that regulate the rapid growth of moso bamboo.

Rapid growth of Moso bamboo (Phyllostachys edulis): Cellular roadmaps, transcriptome dynamics, and environmental factors

Moso bamboo (Phyllostachys edulis) shows remarkably rapid growth (114.5 cm/day), but the underlying biological mechanisms remain unclear. After examining more than 12,750 internodes from more than 510 culms from 17 Moso populations, we identified internode 18 as a representative internode for rapid growth. This internode includes a 2-cm cell division zone (DZ), a cell elongation zone up to 12 cm, and a secondary cell wall (SCW) thickening zone. These zones elongated 11.8 cm, produced approximately 570,000,000 cells, and deposited ∼28 mg g-1 dry weight (DW) lignin and ∼44 mg g-1 DW cellulose daily, far exceeding vegetative growth observed in other plants. We used anatomical, mathematical, physiological, and genomic data to characterize development and transcriptional networks during rapid growth in internode 18. Our results suggest that (1) gibberellin may directly trigger the rapid growth of Moso shoots, (2) decreased cytokinin and increased auxin accumulation may trigger cell DZ elongation, and (3) abscisic acid and mechanical pressure may stimulate rapid SCW thickening via MYB83L. We conclude that internode length involves a possible tradeoff mediated by mechanical pressure caused by rapid growth, possibly influenced by environmental temperature and regulated by genes related to cell division and elongation. Our results provide insight into the rapid growth of Moso bamboo.

Integrative lncRNA landscape reveals lncRNA-coding gene networks in the secondary cell wall biosynthesis pathway of moso bamboo (Phyllostachys edulis)

Background

LncRNAs are extensively involved in plant biological processes. However, the lack of a comprehensive lncRNA landscape in moso bamboo has hindered the molecular study of lncRNAs. Moreover, the role of lncRNAs in secondary cell wall (SCW) biosynthesis of moso bamboo is elusive.

Results

For comprehensively identifying lncRNA throughout moso bamboo genome, we collected 231 RNA-Seq datasets, 1 Iso-Seq dataset, and 1 full-length cDNA dataset. We used a machine learning approach to improve the pipeline of lncRNA identification and functional annotation based on previous studies and identified 37,009 lncRNAs in moso bamboo. Then, we established a network of potential lncRNA-coding gene for SCW biosynthesis and identified SCW-related lncRNAs. We also proposed that a mechanism exists in bamboo to direct phenylpropanoid intermediates to lignin or flavonoids biosynthesis through the PAL/4CL/C4H genes. In addition, we identified 4 flavonoids and 1 lignin-preferred genes in the PAL/4CL/C4H gene families, which gained implications in molecular breeding.

Conclusions

We provided a comprehensive landscape of lncRNAs in moso bamboo. Through analyses, we identified SCW-related lncRNAs and improved our understanding of lignin and flavonoids biosynthesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07953-z.

MicroRNAs play important roles in regulating the rapid growth of the Phyllostachys edulis culm internode

Moso bamboo (Phyllostachys edulis) is a fast-growing species with uneven growth and lignification from lower to upper segments within one internode. MicroRNAs (miRNAs) play a vital role in post-transcriptional regulation in plants. However, how miRNAs regulate fast growth in bamboo internodes is poorly understood. In this study, one moso bamboo internode was divided during early rapid growth into four segments called F4 (bottom) to F1 (upper) and these were then analysed for transcriptomes, miRNAs and degradomes. The F4 segment had a higher number of actively dividing cells as well as a higher content of auxin (IAA), cytokinin (CK) and gibberellin (GA) compared with the F1 segment. RNA-seq analysis showed DNA replication and cell division-associated genes highly expressed in F4 rather than in F1. In total, 63 miRNAs (DEMs) were identified as differentially expressed between F4 and F1. The degradome and the transcriptome indicated that many downstream transcription factors and hormonal responses genes were modulated by DEMs. Several miR-target interactions were further validated by tobacco co-infiltration. Our findings give new insights into miRNA-mediated regulatory pathways in bamboo, and will contribute to a comprehensive understanding of the molecular mechanisms governing rapid growth.

Intercropping improves heavy metal phytoremediation efficiency through changing properties of rhizosphere soil in bamboo plantation

Moso bamboo is considered a potential species for heavy metal (HM) phytoremediation; however, the effect of intercropping on rhizosphere and phytoextraction remains to be elucidated. We comparatively investigated rhizobacteria, soil properties, and phytoextraction efficiency of monoculture and intercropping of Moso bamboo and Sedum plumbizincicola in Cu/Zn/Cd-contaminated soil. Compared with monocultures, intercropping increased the bacterial α-diversity indices (Shannon, Chao1) and the number of biomarkers. Intercropping reduced the contents of soil organic matter (SOM), available nutrients, and Cd and Cu in rhizosphere soils, and reduced the Cd and Zn contents in tissues of sedum. By contrast, Cd and Zn contents in tissues of bamboo increased, and the increase of organic acid in root exudates from intercropping could facilitate the HM absorption. The total amount of Cu, Zn, and Cd removed from the soil in intercropping system was 1.2, 1.9, and 1.8 times than those in monoculture bamboo, respectively. The abundances of Proteobacteria, Acidobacteria, Verrucomicrobia and Actinobacteria were higher in intercropping, playing an important role in soil nutrient cycles and HM remediation. These bacterial communities were closely correlated (P < 0.01) with SOM, available nitrogen, available phosphorus, and HMs. The results suggested this intercropping pattern can increase HM removal efficiency from polluted soils.

Identification and characterisation of monovalent cation/proton antiporters (CPAs) in Phyllostachys edulis and the functional analysis of PheNHX2 in Arabidopsis thaliana

Plant monovalent cation/proton antiporters (CPAs), types of transmembrane transporters, play important roles in resistance to salt stress. In this study, 37 CPA genes from moso bamboo (Phyllostachys edulis) were identified and characterised. The expression profiles of 10 CPA1 genes (PheNHXs) of moso bamboo were detected by qRT-PCR, which showed that they were specifically expressed in six tissues. In addition, the expression of 10 PheNHXs in leaves and roots changed significantly under 150/200 mM NaCl and 100 μM ABA treatments. In particular, the expression of PheNHX2 in leaves and roots was significantly upregulated under NaCl treatment, thus, we cloned PheNHX2 and analysed its function. Subcellular localisation analysis showed that PheNHX2 was located on the vacuolar membrane. Overexpression of PheNHX2 reduced seed germination and root growth of Arabidopsis thaliana under salt stress, as well as severely affecting cellular Na⁺ and K⁺ content, which in turn reduced the salt tolerance of transgenic Arabidopsis. Measurements of physiological indicators, including chlorophyll content, malondialdehyde content, peroxidase and catalase enzyme activities and relative electrical conductivity, all supported this conclusion. Under salt stress, PheNHX2 also inhibited the expression of some stress-related and ion transport-related genes in transgenic Arabidopsis. Overall, these results indicate that overexpression of PheNHX2 reduces the salt tolerance of transgenic Arabidopsis. This investigation establishes a foundation for subsequent functional studies of moso bamboo CPA genes, and it provides a deeper understanding of PheNHX2 regulation in relation to the salt tolerance of moso bamboo.

Transcriptome analysis reveals key genes regulating signaling and metabolic pathways during the growth of moso bamboo (Phyllostachys edulis) shoots

Moso bamboo (Phyllostachys edulis), a high-value bamboo used to produce food (young shoots), building, and industrial goods. To explore key candidate genes regulating signal transduction and metabolic processes during the initiation of stem elongation in moso bamboo, a transcriptome analysis of the shoots during three successive early elongation stages was performed. From cluster and differential expression analyses, 2984 differentially expressed genes (DEGs) were selected for an enrichment analysis. The DEGs were significantly enriched in the plant hormone signal transduction, sugar and starch metabolism, and energy metabolism pathways. Consequently, the DEG expression patterns of these pathways were analyzed, and the plant endogenous hormone and carbon metabolite (including sucrose, total soluble sugar, and starch) contents for each growth stage, of the shoot, were determined. The cytokinin-signaling pathway was continuously active in the three successive elongation stages, in which several cytokinin-signaling genes played indispensable roles. Additionally, many key DEGs regulating sugar, starch metabolism, and energy conversion, which are actively involved in energy production and substrate synthesis during the continuous growth of the shoots, were found. In summary, our study lays a foundation for understanding the mechanisms of moso bamboo growth and provides useful gene resources for breeding through genetic engineering.

Comparative chloroplast genomes: insights into the evolution of the chloroplast genome of Camellia sinensis and the phylogeny of Camellia

BACKGROUND

Chloroplast genome resources can provide useful information for the evolution of plant species. Tea plant (Camellia sinensis) is among the most economically valuable member of Camellia. Here, we determined the chloroplast genome of the first natural triploid Chinary type tea ('Wuyi narcissus' cultivar of Camellia sinensis var. sinensis, CWN) and conducted the genome comparison with the diploid Chinary type tea (Camellia sinensis var. sinensis, CSS) and two types of diploid Assamica type teas (Camellia sinensis var. assamica: Chinese Assamica type tea, CSA and Indian Assamica type tea, CIA). Further, the evolutionary mechanism of the chloroplast genome of Camellia sinensis and the relationships of Camellia species based on chloroplast genome were discussed.

RESULTS

Comparative analysis showed the evolutionary dynamics of chloroplast genome of Camellia sinensis were the repeats and insertion-deletions (indels), and distribution of the repeats, indels and substitutions were significantly correlated. Chinese tea and Indian tea had significant differences in the structural characteristic and the codon usage of the chloroplast genome. Analysis of sequence characterized amplified region (SCAR) using sequences of the intergenic spacers (trnE/trnT) showed none of 292 different Camellia sinensis cultivars had similar sequence characteristic to triploid CWN, but the other four Camellia species did. Estimations of the divergence time showed that CIA diverged from the common ancestor of two Assamica type teas about 6.2 Mya (CI: 4.4-8.1 Mya). CSS and CSA diverged to each other about 0.8 Mya (CI: 0.4-1.5 Mya). Moreover, phylogenetic clustering was not exactly consistent with the current taxonomy of Camellia.

CONCLUSIONS

The repeat-induced and indel-induced mutations were two important dynamics contributed to the diversification of the chloroplast genome in Camellia sinensis, which were not mutually exclusive. Chinese tea and Indian tea might have undergone different selection pressures. Chloroplast transfer occurred during the polyploid evolution in Camellia sinensis. In addition, our results supported the three different domestication origins of Chinary type tea, Chinese Assamica type tea and Indian Assamica type tea. And, the current classification of some Camellia species might need to be further discussed.

Development and Deployment of High-Throughput Retrotransposon-Based Markers Reveal Genetic Diversity and Population Structure of Asian Bamboo

Bamboo, a non-timber grass species, known for exceptionally fast growth is a commercially viable crop. Long terminal repeat (LTR) retrotransposons, the main class I mobile genetic elements in plant genomes, are highly abundant (46%) in bamboo, contributing to genome diversity. They play significant roles in the regulation of gene expression, chromosome size and structure as well as in genome integrity. Due to their random insertion behavior, interspaces of retrotransposons can vary significantly among bamboo genotypes. Capitalizing this feature, inter-retrotransposon amplified polymorphism (IRAP) is a high-throughput marker system to study the genetic diversity of plant species. To date, there are no transposon based markers reported from the bamboo genome and particularly using IRAP markers on genetic diversity. Phyllostachys genus of Asian bamboo is the largest of the Bambusoideae subfamily, with great economic importance. We report structure-based analysis of bamboo genome for the LTR-retrotransposon superfamilies, Ty3-gypsy and Ty1-copia, which revealed a total of 98,850 retrotransposons with intact LTR sequences at both the ends. Grouped into 64,281 clusters/scaffold using CD-HIT-EST software, only 13 clusters of retroelements were found with more than 30 LTR sequences and with at least one copy having all intact protein domains such as gag and polyprotein. A total of 16 IRAP primers were synthesized, based on the high copy numbers of conserved LTR sequences. A study using these IRAP markers on genetic diversity and population structure of 58 Asian bamboo accessions belonging to the genus Phyllostachys revealed 3340 amplicons with an average of 98% polymorphism. The bamboo accessions were collected from nine different provinces of China, as well as from Italy and America. A three phased approach using hierarchical clustering, principal components and a model based population structure divided the bamboo accessions into four sub-populations, PhSP1, PhSP2, PhSP3 and PhSP4. All the three analyses produced significant sub-population wise consensus. Further, all the sub-populations revealed admixture of alleles. The analysis of molecular variance (AMOVA) among the sub-populations revealed high intra-population genetic variation (75%) than inter-population. The results suggest that Phyllostachys bamboos are not well evolutionarily diversified, although geographic speciation could have occurred at a limited level. This study highlights the usability of IRAP markers in determining the inter-species variability of Asian bamboos.

TCP Transcription Factors in Moso Bamboo (Phyllostachys edulis): Genome-Wide Identification and Expression Analysis

TEOSINTE BRANCHED 1, CYCLOIDEA, and PROLIFERATING CELL FACTORS (T), members of a plant-specific gene family, play significant roles during plant growth and development, as well as in response to environmental stress. However, knowledge about this family in moso bamboo (Phyllostachys edulis) is limited. Therefore, in this study, the first genome-wide identification, classification, characterization, and expression pattern analysis of the TCP transcription factor family in moso bamboo was performed. Sixteen TCP members were identified from the moso bamboo genome using a BLASTP algorithm-based method and verified using the Pfam database. Based on a multiple-sequence alignment, the members were divided into two subfamilies, and members of the same family shared highly conserved motif structures. Subcellular localization and transactivation activity analyses of four selected genes revealed that they were nuclear localized and had self-activation activities. Additionally, the expression levels of several PeTCP members were significantly upregulated under abscisic acid, methyl jasmonate, and salicylic acid treatments, indicating that they play crucial plant hormone transduction roles in the processes of plant growth and development, as well as in responses to environmental stresses. Thus, the current study provides previously lacking information on the TCP family in moso bamboo and reveals the potential functions of this gene family in growth and development.

Chromosome-level reference genome and alternative splicing atlas of moso bamboo (Phyllostachys edulis)

Background

Bamboo is one of the most important nontimber forestry products worldwide. However, a chromosome-level reference genome is lacking, and an evolutionary view of alternative splicing (AS) in bamboo remains unclear despite emerging omics data and improved technologies.

Results

Here, we provide a chromosome-level de novo genome assembly of moso bamboo (Phyllostachys edulis) using additional abundance sequencing data and a Hi-C scaffolding strategy. The significantly improved genome is a scaffold N50 of 79.90 Mb, approximately 243 times longer than the previous version. A total of 51,074 high-quality protein-coding loci with intact structures were identified using single-molecule real-time sequencing and manual verification. Moreover, we provide a comprehensive AS profile based on the identification of 266,711 unique AS events in 25,225 AS genes by large-scale transcriptomic sequencing of 26 representative bamboo tissues using both the Illumina and Pacific Biosciences sequencing platforms. Through comparisons with orthologous genes in related plant species, we observed that the AS genes are concentrated among more conserved genes that tend to accumulate higher transcript levels and share less tissue specificity. Furthermore, gene family expansion, abundant AS, and positive selection were identified in crucial genes involved in the lignin biosynthetic pathway of moso bamboo.

Conclusions

These fundamental studies provide useful information for future in-depth analyses of comparative genome and AS features. Additionally, our results highlight a global perspective of AS during evolution and diversification in bamboo.

The association of hormone signalling genes, transcription and changes in shoot anatomy during moso bamboo growth

Moso bamboo is a large, woody bamboo with the highest ecological, economic and cultural value of all the bamboo types and accounts for up to 70% of the total area of bamboo grown. However, the spatiotemporal variation role of moso bamboo shoot during growth period is still unclear. We found that the bamboo shoot growth can be divided into three distinct periods, including winter growth, early growth and late growth based on gene expression and anatomy. In the early growth period, lateral buds germinated from the top of the bamboo joint in the shoot tip. Intercalary meristems grew vigorously during the winter growth period and early growth period, but in the late growth period, mitosis in the intercalary meristems decreased. The expression of cell cycle-associated genes and the quantity of differentially expressed genes were higher in early growth than those in late growth, appearing to be influenced by hormonal concentrations. Gene expression analysis indicates that hormone signalling genes play key roles in shoot growth, while auxin signalling genes play a central role. In situ hybridization analyses illustrate how auxin signalling genes regulate apical dominance, meristem maintenance and lateral bud development. Our study provides a vivid picture of the dynamic changes in anatomy and gene expression during shoot growth in moso bamboo, and how hormone signalling-associated genes participate in moso bamboo shoot growth.

Characterization and expression analysis of the WRKY gene family in moso bamboo

The WRKY family of transcription factors (TFs) is one of the ten largest families of TFs in higher plants and has been implicated in multiple biological processes. Here, we identified 121 WRKY TFs in moso bamboo, including five novel members that were not annotated in the Phyllostachys edulis genomic database. Estimation of the divergence time of paralogous gene pairs revealed an important role of the recent whole-genome duplication in the expansion of the WRKY family. Expression analysis based on quantitative reverse-transcription polymerase chain reaction (qRT-PCR) data revealed that a large number of PheWRKY genes varied significantly under cold or drought stress treatments, which could be defined as abiotic stress-responsive genes. The overexpression of PheWRKY72-2 in Arabidopsis resulted in a decreased sensitivity to drought stress during early seedling growth. PheWRKY72-2 may enhance plant tolerance to stress by functioning as a positive regulator of stoma closure. Our study provides a theoretical foundation and some experimental evidence for further functional verification of the PheWRKY family of TFs.

Genome-wide analysis of VQ motif-containing proteins in Moso bamboo (Phyllostachys edulis)

29 Moso bamboo VQ proteins were genome-wide identified for the first time, and bioinformatics analysis was performed to investigate phylogenetic relationships and evolutionary divergence. The qRT-PCR data show that PeVQ genes response to different stress treatments. Accumulating evidence suggests that VQ motif-containing proteins in rice (Oryza sativa), Arabidopsis (Arabidopsis thaliana), and maize (Zea mays) play fundamental roles in response to various biotic and abiotic stresses. However, little is known about the functions of VQ family proteins in Moso bamboo (Phyllostachys edulis). In this study, we performed a genome-wide bioinformatic analysis and expression profiling of PeVQ genes. A total of 29 VQ genes was identified and divided into seven subgroups (I-VII) based on phylogenetic analysis. Gene structure and conserved motif analysis revealed that 25 of 29 VQ genes contained no introns. Multiple sequence alignment showed that Moso bamboo VQ motif-containing proteins contained five variations of the conserved motif. The time of duplication and divergence of Moso bamboo from rice and maize was calculated using K _s analysis. A heat map was generated using microarray data from 29 Moso bamboo VQ genes suggesting that these genes were expressed in different tissues or developmental stages. Quantitative real-time PCR (qRT-PCR) and promoter analysis indicated that PeVQ genes were differentially regulated following treatment with polyethylene glycol, abscisic acid and salicylic acid. Our results provide a solid foundation for further research of the specific functions of VQ motif-containing proteins in Moso bamboo.

Genome-wide identification and expression analysis of SBP-like transcription factor genes in Moso Bamboo (Phyllostachys edulis)

BACKGROUND

The SQUAMOSA promoter binding protein-like (SPL) proteins are plant-specific transcription factors (TFs) that function in a variety of developmental processes including growth, flower development, and signal transduction. SPL proteins are encoded by a gene family, and these genes have been characterized in two model grass species, Zea mays and Oryza sativa. The SPL gene family has not been well studied in moso bamboo (Phyllostachys edulis), a woody grass species.

RESULTS

We identified 32 putative PeSPL genes in the P. edulis genome. Phylogenetic analysis arranged the PeSPL protein sequences in eight groups. Similarly, phylogenetic analysis of the SBP-like and SBP proteins from rice and maize clustered them into eight groups analogous to those from P. edulis. Furthermore, the deduced PeSPL proteins in each group contained very similar conserved sequence motifs. Our analyses indicate that the PeSPL genes experienced a large-scale duplication event ~15 million years ago (MYA), and that divergence between the PeSPL and OsSPL genes occurred 34 MYA. The stress-response expression profiles and tissue-specificity of the putative PeSPL gene promoter regions showed that SPL genes in moso bamboo have potential biological functions in stress resistance as well as in growth and development. We therefore examined PeSPL gene expression in response to different plant hormone and drought (polyethylene glycol-6000; PEG) treatments to mimic biotic and abiotic stresses. Expression of three (PeSPL10, -12, -17), six (PeSPL1, -10, -12, -17, -20, -31), and nine (PeSPL5, -8, -9, -14, -15, -19, -20, -31, -32) genes remained relatively stable after treating with salicylic acid (SA), gibberellic acid (GA), and PEG, respectively, while the expression patterns of other genes changed. In addition, analysis of tissue-specific expression of the moso bamboo SPL genes during development showed differences in their spatiotemporal expression patterns, and many were expressed at high levels in flowers and leaves.

CONCLUSIONS

The PeSPL genes play important roles in plant growth and development, including responses to stresses, and most of the genes are expressed in different tissues. Our study provides a comprehensive understanding of the PeSPL gene family and may enable future studies on the function and evolution of SPL genes in moso bamboo.

Genome-wide analysis and expression characteristics of small auxin-up RNA (SAUR) genes in moso bamboo (Phyllostachys edulis)

Moso bamboo (Phyllostachys edulis) is well known for its rapid shoot growth. Auxin exerts pleiotropic effects on plant growth. The small auxin-up RNA (SAUR) genes are early auxin-responsive genes involved in plant growth. In total, 38 SAUR genes were identified in P. edulis (PheSAUR). A comprehensive overview of the PheSAUR gene family is presented, including the gene structures, phylogeny, and subcellular location predictions. A transcriptome analysis indicated that 37 (except PheSAUR18) of the PheSAUR genes were expressed during shoot growth process and that the PheSAUR genes were differentially expressed. Furthermore, quantitative real-time PCR analysis indicated that all of the PheSAUR genes could be induced in different tissues of seedlings and that 37 (except PheSAUR41) of the PheSAUR genes were up-regulated after indole-3-acetic acid (IAA) treatment. These results reveal a comprehensive overview of the PheSAUR gene family and may pave the way for deciphering their functions during bamboo development.

Cloning and Preliminary Functional Analysis of PeUGE Gene from Moso Bamboo (Phyllostachys edulis)

UDP-galactose-4-epimerase (UGE) is a key enzyme involved in galactose metabolism by catalyzing the interconversion of UDP-glucose to UDP-galactose. The cDNA encoding UGE was isolated from Phyllostachys edulis by reverse transcription-polymerase chain reaction and by 5' and 3' rapid amplification of cDNA ends, and was designated as PeUGE. The full-length cDNA of PeUGE was 1778 bp, which contained an open reading frame (ORF) encoding a peptide of 420 amino acids, with a calculated molecular mass of 46.58 kDa and a theoretic isoelectric point of 9.07. The genomic sequence corresponding to the ORF of PeUGE was 2656 bp containing 10 exons separated by nine introns. Tissue-specific analysis showed that PeUGE was constitutively expressed with the highest level in shoots, which had an increasing trend with the growth of shoots. PeUGE was induced by abiotic stresses such as drought, salinity, and water stresses. Moreover, chlorophyll fluorescence parameters and lateral roots analysis of transgenic Arabidopsis thaliana plants overexpressing PeUGE systematically confirmed the crucial role of PeUGE in improving the tolerance to abiotic stresses. These results indicated that PeUGE might be one of the key genes involved in the biosynthesis of cell wall polysaccharides during the growth and development of bamboo and in response to stresses, which provided a candidate gene for molecular engineering to improve the quality of bamboo products.

Comprehensive analysis of multi-tissue transcriptome data and the genome-wide investigation of GRAS family in Phyllostachys edulis

GRAS family is one of plant specific transcription factors and plays diverse roles in the regulation of plant growth and development as well as in the plant disease resistance and abiotic stress responses. However, the investigation of GRAS family and multi-tissue gene expression profiles still remains unavailable in bamboo (Phyllostachys edulis). Here, we applied RNA-Seq analysis to monitor global transcriptional changes and investigate expression patterns in the five tissues of Ph. edulis, and analyzed a large-scale transcriptional events and patterns. Moreover, the tissue-specific genes and DEGs in different tissues were detected. For example, DEGs in panicle and leaf tissues were abundant in photosynthesis, glutathione, porphyrin and chlorophyll metabolism, whereas those in shoot and rhizome were majority in glycerophospholipid metabolism. In the portion of Ph. edulis GRAS (PeGRAS) analyses, we performed the analysis of phylogenetic, gene structure, conserved motifs, and analyzed the expression profiles of PeGRASs in response to high light and made a co-expression analysis. Additionally, the expression profiles of PeGRASs were validated using quantitative real-time PCR. Thus, PeGRASs based on dynamics profiles of gene expression is helpful in uncovering the specific biological functions which might be of critical values for bioengineering to improve bamboo breeding in future.

Transcriptome Sequencing and Analysis for Culm Elongation of the World's Largest Bamboo (Dendrocalamus sinicus)

Dendrocalamus sinicus is the world’s largest bamboo species with strong woody culms, and known for its fast-growing culms. As an economic bamboo species, it was popularized for multi-functional applications including furniture, construction, and industrial paper pulp. To comprehensively elucidate the molecular processes involved in its culm elongation, Illumina paired-end sequencing was conducted. About 65.08 million high-quality reads were produced, and assembled into 81,744 unigenes with an average length of 723 bp. A total of 64,338 (79%) unigenes were annotated for their functions, of which, 56,587 were annotated in the NCBI non-redundant protein database and 35,262 were annotated in the Swiss-Prot database. Also, 42,508 and 21,009 annotated unigenes were allocated to gene ontology (GO) categories and clusters of orthologous groups (COG), respectively. By searching against the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG), 33,920 unigenes were assigned to 128 KEGG pathways. Meanwhile, 8,553 simple sequence repeats (SSRs) and 81,534 single-nucleotide polymorphism (SNPs) were identified, respectively. Additionally, 388 transcripts encoding lignin biosynthesis were detected, among which, 27 transcripts encoding Shikimate O-hydroxycinnamoyltransferase (HCT) specifically expressed in D. sinicus when compared to other bamboo species and rice. The phylogenetic relationship between D. sinicus and other plants was analyzed, suggesting functional diversity of HCT unigenes in D. sinicus. We conjectured that HCT might lead to the high lignin content and giant culm. Given that the leaves are not yet formed and culm is covered with sheaths during culm elongation, the existence of photosynthesis of bamboo culm is usually neglected. Surprisedly, 109 transcripts encoding photosynthesis were identified, including photosystem I and II, cytochrome b6/f complex, photosynthetic electron transport and F-type ATPase, and 24 transcripts were characterized as antenna proteins that regarded as the main tool for capturing light of plants, implying stem photosynthesis plays a key role during culm elongation due to the unavailability of its leaf. By real-time quantitative PCR, the expression level of 6 unigenes was detected. The results showed the expression level of all genes accorded with the transcriptome data, which confirm the reliability of the transcriptome data. As we know, this is the first study underline the D. sinicus transcriptome, which will deepen the understanding of the molecular mechanisms of culm development. The results may help variety improvement and resource utilization of bamboos.

Genome-wide identification and characterization of aquaporin gene family in moso bamboo (Phyllostachys edulis)

Aquaporins (AQPs) are known to play a major role in maintaining water and hydraulic conductivity balance in the plant system. Numerous studies have showed AQPs execute multi-function throughout plant growth and development, including water transport, nitrogen, carbon, and micronutrient acquisition etc. However, little information on AQPs is known in bamboo. In this study, we present the first genome-wide identification and characterization of AQP genes in moso bamboo (Phyllostachys edulis) using bioinformatics. In total, 26 AQP genes were identified by homologous analysis, which were divided into four groups (PIPs, TIPs, NIPs, and SIPs) based on the phylogenetic analysis. All the genes were located on 26 different scaffolds respectively on basis of the gene mapped to bamboo genome. Evolutionary analysis indicated that Ph. edulis was more close to Oryza sativa than Zea mays in the genetic relationship. Besides, qRT-PCR was used to analyze gene expression profiles, which revealed that AQP genes were expressed constitutively in all the detected tissues, and were all responsive to the environmental cues such as drought, water, and NaCl stresses. This data suggested that AQPs may play fundamental roles in maintaining normal growth and development of bamboo, which would contribute to better understanding for the complex regulation mechanism involved in the fast-growing process of bamboo. Furthermore, the result could provide valuable information for further research on bamboo functional genomics.

Transcriptome and comparative gene expression analysis of Phyllostachys edulis in response to high light

BACKGROUND

Photosynthesis plays a vital role as an energy source for plant metabolism, and its efficiency may be drastically reduced owing to abiotic stresses. Moso bamboo (Phyllostachys edulis), is a renewable and versatile resource with significant ecological and economic value, which encounters high light stress with large amplitude in natural environment. However, the gene expression profiles in response to high light were elusive in bamboo.

RESULTS

We firstly performed physiological experiments on moso bamboo leaves treated with high light (1200 μmol · m(-2) · s(-1)). Based on the physiological results, three samples of leaves treated with high light for 0 h (CK), 0.5 h (0.5H), and 8 h (8H) were selected to perform further high-throughput RNA sequencing (RNA-Seq), respectively. Then, the transcriptomic result demonstrated that the most genes were expressed at a statistically significant value (FPKM ≥ 1) and the RNA-Seq data were validated via quantitative real time PCR. Moreover, some significant gene expression changes were detected. For instance, 154 differentially expressed genes were detected in 0.5H vs. CK, those in 8H vs. CK were 710, and 429 differentially expressed genes were also identified in 0.5H vs.8 H. Besides, 47 gene annotations closely related to photosynthesis were refined, including 35 genes annotated as light-harvesting chlorophyll a/b-binding (LHC) proteins, 9 LHC-like proteins and 3 PsbSs. Furthermore, the pathway of reactive oxygen species (ROS) in photosynthesis was further analyzed. A total of 171 genes associated with ROS-scavenging were identified. Some up-regulated transcript factors, such as NAC, WRKY, AR2/ERF, and bHLH, mainly concentrated in short-term response, while C2H2, HSF, bZIP, and MYB were largely involved in short and middle terms response to high light.

CONCLUSION

Based on the gene expression analysis of moso bamboo in response to high light, we thus identified the global gene expression patterns, refined the annotations of LHC protein, LHC-like protein and PsbS, detected the pathway of ROS as well as identified ROS-scavenging genes and transcription factors in the regulation of photosynthetic and related metabolisms. These findings maybe provide a starting point to interpret the molecular mechanism of photosynthesis in moso bamboo under high light stress.

Predominance of a single clone of the most widely distributed bamboo species Phyllostachys edulis in East Asia

Phyllostachys edulis, one of the most dominant bamboo species with the leptomorph rhizome system, has been asexually expanding its range into adjacent natural forest sites by shooting new culms. The resulting ecological problems include simplification of stand structure and decline in the species diversity of local flora. In this study, the genetic diversity of P. edulis for the entire distribution range from Japan to China was analyzed using 16 microsatellite markers. Among these, 12 loci were fixed by a single allele, whereas only two alleles were detected for each of the remaining 4 loci; all adult samples shared the same genotype at all loci including the four heterozygous loci. These observations indicate that all current samples from Japan and China comprise an identical clone. The clone is distributed over more than 2,800 km with an estimated biomass of approximately 6.6 × 10(11) kg, which is exceptionally large. Among seedlings from flowering events in 2005 and 2006, 20 different genets were generated by recombination through selfing of a single flowering genet. Predominance of a single clone in the wild and a diverse composition of genets among seedlings suggest that the intermittent flowering of P. edulis in the wild has produced a variety of clones through recombination. However, the resulting seedlings cannot compete with other tree species or adult P. edulis, and almost all adult P. edulis growing in Japan and China likely propagated through vegetative reproduction of a single clone by human transplantation, and subsequently expanded into adjacent forest sites by shooting young sprouts. The relatively small size of the flowering area and rapid culm reproduction has led to the stability of P. edulis communities. However, the low genetic diversity is an important consideration for the long-term management of this prevailing bamboo species.

Plastid phylogenomics of the cool-season grass subfamily: clarification of relationships among early-diverging tribes

Whole plastid genomes are being sequenced rapidly from across the green plant tree of life, and phylogenetic analyses of these are increasing resolution and support for relationships that have varied among or been unresolved in earlier single- and multi-gene studies. Pooideae, the cool-season grass lineage, is the largest of the 12 grass subfamilies and includes important temperate cereals, turf grasses and forage species. Although numerous studies of the phylogeny of the subfamily have been undertaken, relationships among some 'early-diverging' tribes conflict among studies, and some relationships among subtribes of Poeae have not yet been resolved. To address these issues, we newly sequenced 25 whole plastomes, which showed rearrangements typical of Poaceae. These plastomes represent 9 tribes and 11 subtribes of Pooideae, and were analysed with 20 existing plastomes for the subfamily. Maximum likelihood (ML), maximum parsimony (MP) and Bayesian inference (BI) robustly resolve most deep relationships in the subfamily. Complete plastome data provide increased nodal support compared with protein-coding data alone at nodes that are not maximally supported. Following the divergence of Brachyelytrum, Phaenospermateae, Brylkinieae-Meliceae and Ampelodesmeae-Stipeae are the successive sister groups of the rest of the subfamily. Ampelodesmeae are nested within Stipeae in the plastome trees, consistent with its hybrid origin between a phaenospermatoid and a stipoid grass (the maternal parent). The core Pooideae are strongly supported and include Brachypodieae, a Bromeae-Triticeae clade and Poeae. Within Poeae, a novel sister group relationship between Phalaridinae and Torreyochloinae is found, and the relative branching order of this clade and Aveninae, with respect to an Agrostidinae-Brizinae clade, are discordant between MP and ML/BI trees. Maximum likelihood and Bayesian analyses strongly support Airinae and Holcinae as the successive sister groups of a Dactylidinae-Loliinae clade.

Bamboo: an overview on its genetic diversity and characterization

Genetic diversity represents the heritable variation both within and among populations of organisms, and in the context of this paper, among bamboo species. Bamboo is an economically important member of the grass family Poaceae, under the subfamily Bambusoideae. India has the second largest bamboo reserve in Asia after China. It is commonly known as "poor man's timber", keeping in mind the variety of its end use from cradle to coffin. There is a wide genetic diversity of bamboo around the globe and this pool of genetic variation serves as the base for selection as well as for plant improvement. Thus, the identification, characterization and documentation of genetic diversity of bamboo are essential for this purpose. During recent years, multiple endeavors have been undertaken for characterization of bamboo species with the aid of molecular markers for sustainable utilization of genetic diversity, its conservation and future studies. Genetic diversity assessments among the identified bamboo species, carried out based on the DNA fingerprinting profiles, either independently or in combination with morphological traits by several researchers, are documented in the present review. This review will pave the way to prepare the database of prevalent bamboo species based on their molecular characterization.

Developing genome-wide microsatellite markers of bamboo and their applications on molecular marker assisted taxonomy for accessions in the genus Phyllostachys

Morphology-based taxonomy via exiguously reproductive organ has severely limitation on bamboo taxonomy, mainly owing to infrequent and unpredictable flowering events of bamboo. Here, we present the first genome-wide analysis and application of microsatellites based on the genome of moso bamboo (Phyllostachys edulis) to assist bamboo taxonomy. Of identified 127,593 microsatellite repeat-motifs, the primers of 1,451 microsatellites were designed and 1,098 markers were physically mapped on the genome of moso bamboo. A total of 917 markers were successfully validated in 9 accessions with ~39.8% polymorphic potential. Retrieved from validated microsatellite markers, 23 markers were selected for polymorphic analysis among 78 accessions and 64 alleles were detected with an average of 2.78 alleles per primers. The cluster result indicated the majority of the accessions were consistent with their current taxonomic classification, confirming the suitability and effectiveness of the developed microsatellite markers. The variations of microsatellite marker in different species were confirmed by sequencing and in silico comparative genome mapping were investigated. Lastly, a bamboo microsatellites database (http://www.bamboogdb.org/ssr) was implemented to browse and search large information of bamboo microsatellites. Consequently, our results of microsatellite marker development are valuable for assisting bamboo taxonomy and investigating genomic studies in bamboo and related grass species.

Identification, cross-taxon transferability and application of full-length cDNA SSR markers in Phyllostachys pubescens

Current databases of Phyllostachys pubescens full-length cDNAs (FL-cDNAs) provide a rich source of sequences for the development of potential FL-cDNA simple sequence repeat (SSR) markers. We screened 10,608 P. pubescens cDNAs, discovering 1614 SSRs in 1382 SSR-containing FL-cDNAs. The SSRs were more abundant within transposable elements (TEs) than expressed sequence tags (ESTs) and genome survey sequences (GSSs), and specific dinucleotide repeats tended to associate with particular TE families: (TA)n with En/Spm and (CT)n with Mutator. A selected panel of 100 FL-cDNAs containing type I SSRs yielded 68 functional SSR markers with an average polymorphism information content (PIC) value of 0.12, among which 22 loci contained polymorphisms. These markers became less transferrable (83.1% → 69.9% → 49.3%) but more polymorphic (79.4% → 92.3% → 92.8%) with increasing phylogenetic distance (intra-genus → intra-subtribe → intra-family). Transferability and polymorphism also depended on the location of the marker, with those located in the coding region being more transferrable (69.1%) and less polymorphic (89.4%) than those in the 5'-UTR (63.4% transferable, 90.7% polymorphic) and the 3'-UTR (61.8% transferable, 91.4% polymorphic). As proof of principle, we were able to use our FL-cDNA SSR markers to identify the parental stocks in interspecific hybrids of bamboo within and beyond P. pubescens, and estimate the outcrossing rate for P. pubescens. Our research should facilitate molecular breeding in bamboo species where original genetic markers are scarce.

Phylogeny in defining model plants for lignocellulosic ethanol production: a comparative study of Brachypodium distachyon, wheat, maize, and Miscanthus x giganteus leaf and stem biomass

The production of ethanol from pretreated plant biomass during fermentation is a strategy to mitigate climate change by substituting fossil fuels. However, biomass conversion is mainly limited by the recalcitrant nature of the plant cell wall. To overcome recalcitrance, the optimization of the plant cell wall for subsequent processing is a promising approach. Based on their phylogenetic proximity to existing and emerging energy crops, model plants have been proposed to study bioenergy-related cell wall biochemistry. One example is Brachypodium distachyon, which has been considered as a general model plant for cell wall analysis in grasses. To test whether relative phylogenetic proximity would be sufficient to qualify as a model plant not only for cell wall composition but also for the complete process leading to bioethanol production, we compared the processing of leaf and stem biomass from the C3 grasses B. distachyon and Triticum aestivum (wheat) with the C4 grasses Zea mays (maize) and Miscanthus x giganteus, a perennial energy crop. Lambda scanning with a confocal laser-scanning microscope allowed a rapid qualitative analysis of biomass saccharification. A maximum of 108-117 mg ethanol·g(-1) dry biomass was yielded from thermo-chemically and enzymatically pretreated stem biomass of the tested plant species. Principal component analysis revealed that a relatively strong correlation between similarities in lignocellulosic ethanol production and phylogenetic relation was only given for stem and leaf biomass of the two tested C4 grasses. Our results suggest that suitability of B. distachyon as a model plant for biomass conversion of energy crops has to be specifically tested based on applied processing parameters and biomass tissue type.

Discovery and comparative profiling of microRNAs in representative monopodial bamboo (Phyllostachys edulis) and sympodial bamboo (Dendrocalamus latiflorus)

Background

According to the growth pattern of bamboo, sympodial bamboo and monopodial bamboo are considered as two mainly kinds of bamboo. They have different phenotypes and different characteristics in developmental stage. Much attention had been paid on the study of bamboo cultivation, processing, physiology, biochemistry and molecular biology, which had made great progresses in the last decade, especially for the highlighted achievement of the bamboo genomics. However, there is no information available on concerning comparative profiling of miRNAs between sympodial bamboo and monopodial bamboo, which might play important roles in the regulation of bamboo development.

Methodology/Principal Findings

We identified the profiles of small RNAs using leaf tissues from one sympodial bamboo i.e. moso bamboo (Phyllostachys edulis) and another monopodial bamboo i.e. ma bamboo (Dendrocalamus latiflorus). The result showed that there were 19,295,759 and 11,513,888 raw sequence reads, in which 92 and 69 conserved miRNAs, as well as 95 and 62 novel miRNAs were identified in moso bamboo and ma bamboo, respectively. The ratio of high conserved miRNA families in ma bamboo is more than that in moso bamboo. In addition, a total of 49 and 106 potential targets were predicted in moso bamboo and ma bamboo, respectively, in which several targets for novel miRNAs are transcription factors that play important roles in plant development. More importantly, annotation of differentially expressed target genes was performed based on the analysis of pathway and gene ontology terms enrichment.

Conclusions/Significance

This study provides the first large-scale sight of discovery and comparative characterization of miRNAomes between two representative bamboos belonged to sympodial bamboo and monopodial bamboo, respectively. Although it will be necessary to validate the function of miRNAs through more experimental research in further, these results lay a foundation for unraveling the miRNA-mediated molecular processes in different kinds of bamboo.

Thirteen Camellia chloroplast genome sequences determined by high-throughput sequencing: genome structure and phylogenetic relationships

BACKGROUND

Camellia is an economically and phylogenetically important genus in the family Theaceae. Owing to numerous hybridization and polyploidization, it is taxonomically and phylogenetically ranked as one of the most challengingly difficult taxa in plants. Sequence comparisons of chloroplast (cp) genomes are of great interest to provide a robust evidence for taxonomic studies, species identification and understanding mechanisms that underlie the evolution of the Camellia species.

RESULTS

The eight complete cp genomes and five draft cp genome sequences of Camellia species were determined using Illumina sequencing technology via a combined strategy of de novo and reference-guided assembly. The Camellia cp genomes exhibited typical circular structure that was rather conserved in genomic structure and the synteny of gene order. Differences of repeat sequences, simple sequence repeats, indels and substitutions were further examined among five complete cp genomes, representing a wide phylogenetic diversity in the genus. A total of fifteen molecular markers were identified with more than 1.5% sequence divergence that may be useful for further phylogenetic analysis and species identification of Camellia. Our results showed that, rather than functional constrains, it is the regional constraints that strongly affect sequence evolution of the cp genomes. In a substantial improvement over prior studies, evolutionary relationships of the section Thea were determined on basis of phylogenomic analyses of cp genome sequences.

CONCLUSIONS

Despite a high degree of conservation between the Camellia cp genomes, sequence variation among species could still be detected, representing a wide phylogenetic diversity in the genus. Furthermore, phylogenomic analysis was conducted using 18 complete cp genomes and 5 draft cp genome sequences of Camellia species. Our results support Chang's taxonomical treatment that C. pubicosta may be classified into sect. Thea, and indicate that taxonomical value of the number of ovaries should be reconsidered when classifying the Camellia species. The availability of these cp genomes provides valuable genetic information for accurately identifying species, clarifying taxonomy and reconstructing the phylogeny of the genus Camellia.

Identification of putative orthologous genes for the phylogenetic reconstruction of temperate woody bamboos (Poaceae: Bambusoideae)

The temperate woody bamboos (Arundinarieae) are highly diverse in morphology but lack a substantial amount of genetic variation. The taxonomy of this lineage is intractable, and the relationships within the tribe have not been well resolved. Recent studies indicated that this tribe could have a complex evolutionary history. Although phylogenetic studies of the tribe have been carried out, most of these phylogenetic reconstructions were based on plastid data, which provide lower phylogenetic resolution compared with nuclear data. In this study, we intended to identify a set of desirable nuclear genes for resolving the phylogeny of the temperate woody bamboos. Using two different methodologies, we identified 209 and 916 genes, respectively, as putative single copy orthologous genes. A total of 112 genes was successfully amplified and sequenced by next-generation sequencing technologies in five species sampled from the tribe. As most of the genes exhibited intra-individual allele heterozygotes, we investigated phylogenetic utility by reconstructing the phylogeny based on individual genes. Discordance among gene trees was observed and, to resolve the conflict, we performed a range of analyses using BUCKy and HybTree. While caution should be taken when inferring a phylogeny from multiple conflicting genes, our analysis indicated that 74 of the 112 investigated genes are potential markers for resolving the phylogeny of the temperate woody bamboos.

BambooGDB: a bamboo genome database with functional annotation and an analysis platform

Bamboo, as one of the most important non-timber forest products and fastest-growing plants in the world, represents the only major lineage of grasses that is native to forests. Recent success on the first high-quality draft genome sequence of moso bamboo (Phyllostachys edulis) provides new insights on bamboo genetics and evolution. To further extend our understanding on bamboo genome and facilitate future studies on the basis of previous achievements, here we have developed BambooGDB, a bamboo genome database with functional annotation and analysis platform. The de novo sequencing data, together with the full-length complementary DNA and RNA-seq data of moso bamboo composed the main contents of this database. Based on these sequence data, a comprehensively functional annotation for bamboo genome was made. Besides, an analytical platform composed of comparative genomic analysis, protein–protein interactions network, pathway analysis and visualization of genomic data was also constructed. As discovery tools to understand and identify biological mechanisms of bamboo, the platform can be used as a systematic framework for helping and designing experiments for further validation. Moreover, diverse and powerful search tools and a convenient browser were incorporated to facilitate the navigation of these data. As far as we know, this is the first genome database for bamboo. Through integrating high-throughput sequencing data, a full functional annotation and several analysis modules, BambooGDB aims to provide worldwide researchers with a central genomic resource and an extensible analysis platform for bamboo genome. BambooGDB is freely available at http://www.bamboogdb.org/.

Database URL: http://www.bamboogdb.org

Validation of reference genes aiming accurate normalization of qRT-PCR data in Dendrocalamus latiflorus Munro

BACKGROUND

Dendrocalamus latiflorus Munro distributes widely in subtropical areas and plays vital roles as valuable natural resources. The transcriptome sequencing for D. latiflorus Munro has been performed and numerous genes especially those predicted to be unique to D. latiflorus Munro were revealed. qRT-PCR has become a feasible approach to uncover gene expression profiling, and the accuracy and reliability of the results obtained depends upon the proper selection of stable reference genes for accurate normalization. Therefore, a set of suitable internal controls should be validated for D. latiflorus Munro.

RESULTS

In this report, twelve candidate reference genes were selected and the assessment of gene expression stability was performed in ten tissue samples and four leaf samples from seedlings and anther-regenerated plants of different ploidy. The PCR amplification efficiency was estimated, and the candidate genes were ranked according to their expression stability using three software packages: geNorm, NormFinder and Bestkeeper. GAPDH and EF1α were characterized to be the most stable genes among different tissues or in all the sample pools, while CYP showed low expression stability. RPL3 had the optimal performance among four leaf samples. The application of verified reference genes was illustrated by analyzing ferritin and laccase expression profiles among different experimental sets. The analysis revealed the biological variation in ferritin and laccase transcript expression among the tissues studied and the individual plants.

CONCLUSIONS

geNorm, NormFinder, and BestKeeper analyses recommended different suitable reference gene(s) for normalization according to the experimental sets. GAPDH and EF1α had the highest expression stability across different tissues and RPL3 for the other sample set. This study emphasizes the importance of validating superior reference genes for qRT-PCR analysis to accurately normalize gene expression of D. latiflorus Munro.

BambooGDB: a bamboo genome database with functional annotation and an analysis platform

Bamboo, as one of the most important non-timber forest products and fastest-growing plants in the world, represents the only major lineage of grasses that is native to forests. Recent success on the first high-quality draft genome sequence of moso bamboo (Phyllostachys edulis) provides new insights on bamboo genetics and evolution. To further extend our understanding on bamboo genome and facilitate future studies on the basis of previous achievements, here we have developed BambooGDB, a bamboo genome database with functional annotation and analysis platform. The de novo sequencing data, together with the full-length complementary DNA and RNA-seq data of moso bamboo composed the main contents of this database. Based on these sequence data, a comprehensively functional annotation for bamboo genome was made. Besides, an analytical platform composed of comparative genomic analysis, protein-protein interactions network, pathway analysis and visualization of genomic data was also constructed. As discovery tools to understand and identify biological mechanisms of bamboo, the platform can be used as a systematic framework for helping and designing experiments for further validation. Moreover, diverse and powerful search tools and a convenient browser were incorporated to facilitate the navigation of these data. As far as we know, this is the first genome database for bamboo. Through integrating high-throughput sequencing data, a full functional annotation and several analysis modules, BambooGDB aims to provide worldwide researchers with a central genomic resource and an extensible analysis platform for bamboo genome. BambooGDB is freely available at http://www.bamboogdb.org/. Database URL: http://www.bamboogdb.org.

Transcriptome sequencing and analysis of the fast growing shoots of moso bamboo (Phyllostachys edulis)

Background

The moso bamboo, a large woody bamboo with the highest ecological, economic, and cultural value of all bamboos, has one of the highest growth speeds in the world. Genetic research into moso bamboo has been scarce, partly because of the lack of previous genomic resources. In the present study, for the first time, we performed de novo transcriptome sequencing and mapped to the moso bamboo genomic resources (reference genome and genes) to produce a comprehensive dataset for the fast growing shoots of moso bamboo.

Results

The fast growing shoots mixed with six different heights and culms after leaf expansion of moso bamboo transcriptome were sequenced using the Illumina HiSeq™ 2000 sequencing platform, respectively. More than 80 million reads including 65,045,670 and 68,431,884 clean reads were produced in the two libraries. More than 81% of the reads were matched to the reference genome, and nearly 50% of the reads were matched to the reference genes. The genes with log 2 ratio > 2 or < −2 (P<0.001) were characterized as the most differentially expressed genes. 6,076 up-regulated and 4,613 down-regulated genes were classified into functional categories. Candidate genes which mainly involved transcript factors, plant hormones, cell cycle regulation, cell wall metabolism and cell morphogenesis genes were further analyzed and they may form a network that regulates the fast growth of moso bamboo shoots.

Conclusion

Firstly, our data provides the most comprehensive transcriptomic resource for moso bamboo to date. Candidate genes have been identified and they are potentially involved in the growth and development of moso bamboo. The results give a better insight into the mechanisms of moso bamboo shoots rapid growth and provide gene resources for improving plant growth.

Next-generation sequencing-based mRNA and microRNA expression profiling analysis revealed pathways involved in the rapid growth of developing culms in Moso bamboo

BACKGROUND

As one of the fastest-growing lignocellulose-abundant plants on Earth, bamboos can reach their final height quickly due to the expansion of individual internodes already present in the buds; however, the molecular processes underlying this phenomenon remain unclear. Moso bamboo (Phyllostachys heterocycla cv. Pubescens) internodes from four different developmental stages and three different internodes within the same stage were used in our study to investigate the molecular processes at the transcriptome and post-transcriptome level.

RESULTS

Our anatomical observations indicated the development of culms was dominated by cell division in the initial stages and by cell elongation in the middle and late stages. The four major endogenous hormones appeared to actively promote culm development. Using next-generation sequencing-based RNA-Seq, mRNA and microRNA expression profiling technology, we produced a transcriptome and post-transcriptome in possession of a large fraction of annotated Moso bamboo genes, and provided a molecular basis underlying the phenomenon of sequentially elongated internodes from the base to the top. Several key pathways such as environmental adaptation, signal transduction, translation, transport and many metabolisms were identified as involved in the rapid elongation of bamboo culms.

CONCLUSIONS

This is the first report on the temporal and spatial transcriptome and gene expression and microRNA profiling in a developing bamboo culms. In addition to gaining more insight into the unique growth characteristics of bamboo, we provide a good case study to analyze gene, microRNA expression and profiling of non-model plant species using high-throughput short-read sequencing. Also, we demonstrate that the integrated analysis of our multi-omics data, including transcriptome, post-transcriptome, proteome, yield more complete representations and additional biological insights, especially the complex dynamic processes occurring in Moso bamboo culms.

Phylogenomic analyses of nuclear genes reveal the evolutionary relationships within the BEP clade and the evidence of positive selection in Poaceae

BEP clade of the grass family (Poaceae) is composed of three subfamilies, i.e. Bambusoideae, Ehrhartoideae, and Pooideae. Controversies on the phylogenetic relationships among three subfamilies still persist in spite of great efforts. However, previous evidence was mainly provided from plastid genes with only a few nuclear genes utilized. Given different evolutionary histories recorded by plastid and nuclear genes, it is indispensable to uncover their relationships based on nuclear genes. Here, eleven species with whole-sequenced genome and six species with transcriptomic data were included in this study. A total of 121 one-to-one orthologous groups (OGs) were identified and phylogenetic trees were reconstructed by different tree-building methods. Genes which might have undergone positive selection and played important roles in adaptive evolution were also investigated from 314 and 173 one-to-one OGs in two bamboo species and 14 grass species, respectively. Our results support the ((B, P) E) topology with high supporting values. Besides, our findings also indicate that 24 and nine orthologs with statistically significant evidence of positive selection are mainly involved in abiotic and biotic stress response, reproduction and development, plant metabolism and enzyme etc. from two bamboo species and 14 grass species, respectively. In summary, this study demonstrates the power of phylogenomic approach to shed lights on the evolutionary relationships within the BEP clade, and offers valuable insights into adaptive evolution of the grass family.

Combinational effect of mutational bias and translational selection for translation efficiency in tomato (Solanum lycopersicum) cv. Micro-Tom

We conducted a comprehensive analysis of codon usage bias (CUB) based on the available non-redundant full-length cDNA (nrFLcDNA) and expressed sequence tags (ESTs) data of cultivar Micro-Tom and evaluated the associations of observed CUB and measurements of transcriptional and translational effectiveness. The analysis presented in our study suggests a correlation, which is negative but highly correlated between Axis 1 and GC3s (r=-0.827, P<0.01), indicating that mutational bias has a significant and dominant repressive role to the choices of GC3. We also observed a strong positive correlation between codon adaptation index (CAI) and translational adaptation index (tAIg) (0.407, P<0.01), which demonstrates the facilitation of efficient translation by the optimal codon usage patterns of the highly expressed genes. We believe that the complete set of optimal codon usage patterns detected in this study will serve as a model to enhance the transgenesis in the studied cultivar of Solanum lycopersicum.

The draft genome of the fast-growing non-timber forest species moso bamboo (Phyllostachys heterocycla)

Bamboo represents the only major lineage of grasses that is native to forests and is one of the most important non-timber forest products in the world. However, no species in the Bambusoideae subfamily has been sequenced. Here, we report a high-quality draft genome sequence of moso bamboo (P. heterocycla var. pubescens). The 2.05-Gb assembly covers 95% of the genomic region. Gene prediction modeling identified 31,987 genes, most of which are supported by cDNA and deep RNA sequencing data. Analyses of clustered gene families and gene collinearity show that bamboo underwent whole-genome duplication 7-12 million years ago. Identification of gene families that are key in cell wall biosynthesis suggests that the whole-genome duplication event generated more gene duplicates involved in bamboo shoot development. RNA sequencing analysis of bamboo flowering tissues suggests a potential connection between drought-responsive and flowering genes.

Limitations, progress and prospects of application of biotechnological tools in improvement of bamboo-a plant with extraordinary qualities

Bamboos (family Poaceae) are the most beautiful and useful plants on the Earth, mainly found in the tropical and sub-tropical regions of the world. Bamboos are fast growing and early maturing, but lack of proper management of bamboo resources is leading to rapid reduction of the existing bamboosetum. Bamboo propagation through seeds is limited due to long flowering cycle of upto 120 years, seed sterility and short seed viability. Infrequent and unpredictable flowering events coupled with peculiar monocarpic behaviour i.e. flowering once before culm death, and extensive genome polyploidization are additional challenges for this woody group. Similarly, vegetative propagation by cuttings, offsets and rhizomes are also inadequate to cope up with the demand of planting stock due to large propagule size, limited availability, seasonal dependence, low multiplication rate and rooting percentage. Therefore, attempts have been made to propagate bamboos through in vitro techniques. In vitro flowering has also been achieved successfully in some bamboo species. Classification systems proposed to date need further support, as taxonomic delineation at lower levels is still lacking sufficient resolution. Tremendous advancement in molecular markers holds the promise to address the needs of bamboo taxonomy (systematics and identification) and diversity studies. Successful application of molecular marker techniques has been achieved in several bamboo species although, more studies are required to understand the population structure and genetic diversity of bamboos in a better way. In addition, some efforts have also been made to clone important genes from bamboos and also for genetic transformation using Agrobacterium and particle bombardment methods. An overview of the recent developments made in improvement of bamboos through in vitro propagation, molecular marker technologies, cloning, and transformation and transgenics has been presented. The future potential of improvement of bamboos using modern biotechnological tools has also been discussed.

Transcriptome sequencing and de novo analysis for Ma bamboo (Dendrocalamus latiflorus Munro) using the Illumina platform

BACKGROUND

Bamboo occupies an important phylogenetic node in the grass family with remarkable sizes, woodiness and a striking life history. However, limited genetic research has focused on bamboo partially because of the lack of genomic resources. The advent of high-throughput sequencing technologies enables generation of genomic resources in a short time and at a minimal cost, and therefore provides a turning point for bamboo research. In the present study, we performed de novo transcriptome sequencing for the first time to produce a comprehensive dataset for the Ma bamboo (Dendrocalamus latiflorus Munro).

RESULTS

The Ma bamboo transcriptome was sequenced using the Illumina paired-end sequencing technology. We produced 15,138,726 reads and assembled them into 103,354 scaffolds. A total of 68,229 unigenes were identified, among which 46,087 were annotated in the NCBI non-redundant protein database and 28,165 were annotated in the Swiss-Prot database. Of these annotated unigenes, 11,921 and 10,147 unigenes were assigned to gene ontology categories and clusters of orthologous groups, respectively. We could map 45,649 unigenes onto 292 pathways using the Kyoto Encyclopedia of Genes and Genomes Pathway database. The annotated unigenes were compared against Moso bamboo, rice and millet. Unigenes that did not match any of those three sequence datasets are considered to be Ma bamboo unique. We predicted 105 unigenes encoding eight key enzymes involved in lignin biosynthesis. In addition, 621 simple sequence repeats (SSRs) were detected.

CONCLUSION

Our data provide the most comprehensive transcriptomic resource currently available for D. latiflorus Munro. Candidate genes potentially involved in growth and development were identified, and those predicted to be unique to Ma bamboo are expected to give a better insight on Ma bamboo gene diversity. Numerous SSRs characterized contributed to marker development. These data constitute a new valuable resource for genomic studies on D. latiflorus Munro and, more generally, bamboo.

Characterization and primary functional analysis of phenylalanine ammonia-lyase gene from Phyllostachys edulis

Phenylalanine ammonia-lyase (PAL) catalyzes the first reaction in phenylpropanoid pathway leading to the production of phenolic compounds with a wide range of biological functions. The cDNA encoding PAL was isolated from Phyllostachys edulis by reverse transcription-polymerase chain reaction (RT-PCR) and by 5' and 3' rapid amplification of cDNA ends, and was designated as PePAL. The full length of PePAL was 2,503 bp which contained an open reading frame (ORF) encoding a peptide of 701 amino acids, with a theoretic isoelectric point of 6.49 and a calculated molecular mass of 75.7 kDa. PePAL was heterologously expressed in Escherichia coli and the recombinant proteins exhibited both PAL and tyrosine ammonia-lyase (TAL) activities. The optimum temperature and pH of the recombinant PePAL were 50 °C and 8.5-9.0, respectively. The K (m) and V (max) values for L-phenylalanine was calculated as 422 μM and 45.9 nM s⁻¹, while for L-tyrosine were 78 μM and 7.09 nM s⁻¹, respectively. Tissue-specific expression assay showed that PePAL expressed highest in stem and sheath, followed by leaf, and lowest in root. Though the accumulation of PePAL proteins was observed in all these four organs by Western blotting, the highest was detected in leaf. Immunohistochemistry study showed that PePAL was localized primarily in vascular bundles and part of sclerenchyma cells of leaf, sheath and root. These results suggested that PePAL had similar expression pattern and biochemical properties with PALs in other plants, which laid the basis for molecular engineering to improve the quality of bamboo products.

KEY MESSAGE

PePAL was a protein with bifunctional enzyme activities of PAL and TAL as shown in vitro assays, and localized primarily in bamboo vascular bundles.

The role of CCoAOMT1 and COMT1 in Arabidopsis anthers

Arabidopsis caffeoyl coenzyme A dependent O-methyltransferase 1 (CCoAOMT1) and caffeic acid O-methyltransferase 1 (COMT1) display a similar substrate profile although with distinct substrate preferences and are considered the key methyltransferases (OMTs) in the biosynthesis of lignin monomers, coniferyl and sinapoylalcohol. Whereas CCoAOMT1 displays a strong preference for caffeoyl coenzyme A, COMT1 preferentially methylates 5-hydroxyferuloyl CoA derivatives and also performs methylation of flavonols with vicinal aromatic dihydroxy groups, such as quercetin. Based on different knockout lines, phenolic profiling, and immunohistochemistry, we present evidence that both enzymes fulfil distinct, yet different tasks in Arabidopsis anthers. CCoAOMT1 besides its role in vascular tissues can be localized to the tapetum of young stamens, contributing to the biosynthesis of spermidine phenylpropanoid conjugates. COMT1, although present in the same organ, is not localized in the tapetum, but in two directly adjacent cells layers, the endothecium and the epidermal layer of stamens. In vivo localization and phenolic profiling of comt1 plants provide evidence that COMT1 neither contributes to the accumulation of spermidine phenylpropanoid conjugates nor to the flavonol glycoside pattern of pollen grains.