Identification of genes involved in bamboo fiber development

Transcriptomic analysis reveals the flooding tolerant mechanism in flooding tolerant line and abscisic acid treated soybean

Soybean is highly sensitive to flooding stress and exhibits markedly reduced plant growth and grain yield under flooding conditions. To explore the mechanisms underlying initial flooding tolerance in soybean, RNA sequencing-based transcriptomic analysis was performed using a flooding-tolerant line and ABA-treated soybean. A total of 31 genes included 12 genes that exhibited similar temporal patterns were commonly changed in these plant groups in response to flooding and they were mainly involved in RNA regulation and protein metabolism. The mRNA expression of matrix metalloproteinase, glucose-6-phosphate isomerase, ATPase family AAA domain-containing protein 1, and cytochrome P450 77A1 was up-regulated in wild-type soybean under flooding conditions; however, no changes were detected in the flooding-tolerant line or ABA-treated soybean. The mRNA expression of cytochrome P450 77A1 was specifically up-regulated in root tips by flooding stress, but returned to the level found in control plants following treatment with the P450 inhibitor uniconazole. The survival ratio and root fresh weight of plants were markedly improved by 3-h uniconazole treatment under flooding stress. Taken together, these results suggest that cytochrome P450 77A1 is suppressed by uniconazole treatment and that this inhibition may enhance soybean tolerance to flooding stress.

Overexpression of human peroxisomal enoyl-CoA delta isomerase2 HsPECI2, an ortholog of bamboo expressed during gregarious flowering alters salinity stress responses and polar lipid content in tobacco

Peroxisomal enoyl-CoA delta isomerase2 (PECI2) is one of the key enzymes that has critical role in lipid metabolism and plant development during salt stress. Seven out of ten tobacco plants overexpressing human PECI2 (HsPECI2) with PTS1-sequence showed hypersensitivity to salt. Under salt-stress, T2 transformed plants (HsPECI2) displayed reduced primary root, delayed shoot-growth, and visibly smaller rosette leaves turning pale yellow as compared to the pKYLX71 vector control plant. Also, we found altered reactive oxygen species (ROS) levels and reduced catalase activity in 100mM sodium chloride (NaCl) treated HsPECI2 transformed plant compared with the pKYLX71 counterpart. ESI-MS/MS data showed that the polar lipids were differentially modulated upon salt treatment in HsPECI2 transformed and pKYLX71 plants as compared with the respective untreated counterpart. Notably, the levels of monogalactosyldiacylglycerol and phosphatidic acid varied significantly, whereas phosphatidylcholine, phosphatidylserine and digalactosyldiacylglycerol contents were moderately upregulated. In parallel, abscisic acid (ABA) responsiveness assay confirmed insensitivity of HsPECI2 transformed plant towards ABA. Overall our data proclaim that HsPECI2 play multifunctional role in normal development and response to salinity stress apart from its primary role in β-oxidation.

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.

Reference gene selection for quantitative real-time PCR normalization in Reaumuria soongorica

Despite its superiority for evaluating gene expression, real-time quantitative polymerase chain reaction (qPCR) results can be significantly biased by the use of inappropriate reference genes under different experimental conditions. Reaumuria soongorica is a dominant species of desert ecosystems in arid central Asia. Given the increasing interest in ecological engineering and potential genetic resources for arid agronomy, it is important to analyze gene function. However, systematic evaluation of stable reference genes should be performed prior to such analyses. In this study, the stabilities of 10 candidate reference genes were analyzed under 4 kinds of abiotic stresses (drought, salt, dark, and heat) within 4 accessions (HG010, HG020, XGG030, and XGG040) from 2 different habitats using 3 algorithms (geNorm, NormFinder, and BestKeeper). After validation of the ribulose-1,5-bisphosphate carboxylase/oxygenase large unite (rbcL) expression pattern, our data suggested that histone H2A (H2A) and eukaryotic initiation factor 4A-2 (EIF4A2) were the most stable reference genes, cyclophilin (CYCL) was moderate, and elongation factor 1α (EF1α) was the worst choice. This first systematic analysis for stably expressed genes will facilitate future functional analyses and deep mining of genetic resources in R. soongorica and other species of the Reaumuria genus.

Functional characterization of a serine-threonine protein kinase from Bambusa balcooa that implicates in cellulose overproduction and superior quality fiber formation

BACKGROUND

Molecular markers allow rapid identification of biologically important germplasm/s having desired character. Previously we have reported a genotype specific molecular marker, Balco1128 [GenBank ID EU258678] of Bambusa balcooa containing an ORF (375 bp) having high similarity with receptor like cytoplasmic kinase of Arabidopsis and Oryza. Balco1128 was found to be associated only with bamboo genotypes endowed with high cellulose and low lignin contents of fibers. Under the above backdrop, it was necessitated to characterize this genetic marker for better understanding of its biological significance in context of superior quality fiber development.

RESULTS

The full length cDNA (3342 bp) of BbKst, a serine-threonine protein kinase was isolated from B. balcooa comprising of six LRR domains at the N-terminal end and a kinase domain at the C-terminal end. Bacteria-expressed BbKst-kinase domain (3339 bp long) showed Mg(2+) dependent kinase activity at pH 7.0, 28°C. Bioinformatics study followed by phospho-amino analysis further confirmed that BbKst-kinase belongs to the serine/threonine protein kinase family. Transcript analysis of the BbKst gene following RNA slot blot hybridization and qPCR revealed higher expression of BbKst during initiation and elongation stages of fiber development. Tissue specific expression studies showed much higher expression of BbKst transcript in stems and internodes of B. balcooa than in leaves and rhizomes. Southern analysis revealed single copy insertion of BbKst in most of the Agrobacterium mediated transgenic tobacco plants. Real-time PCR detected 150-200 fold enhanced expression of BbKst in different T1 tobacco lines than that of the vector transformed plants. Heterologous expression of BbKst under control of 35S promoter in transgenic tobacco showed high cellulose deposition in the xylem fibers. Number of xylary fibers was higher in transgenic T0 and T1 plants than that of empty-vector transformed tobacco plants offering enhanced mechanical strength to the transgenic plants, which was also substantiated by their strong upright phenotypes, significantly higher cellulose contents, flexibility coefficient, slenderness ratio, and lower Runkel ratio of the fibers.

CONCLUSIONS

This finding clearly demonstrated that BbKst gene (GenBank ID JQ432560) encodes a serine/threonine protein kinase. BbKst induced higher cellulose deposition/synthesis in transgenic tobacco plants, an important attribute of fiber quality bestowing additional strength to the plant.

Selection of reference genes for quantitative real-time PCR in bamboo (Phyllostachys edulis)

Background

The Moso bamboo (Phyllostachys edulis) is one of the most important forestry resources and plays essential ecological roles in southern China. A draft nuclear genome sequence is expected to be publicly available in the near future; an explosion of gene expression data related to the unique traits of Moso bamboo will undoubtedly follow. Reverse transcription quantitative real-time PCR ((RT-)qPCR) is a widely used method for gene expression analysis. A necessary prerequisite of exact and reliable data is the accurate choice of reference genes.

Result

In this study, 14 candidate reference genes were chosen, and their expression levels were assessed by (RT-)qPCR in a set of six tissue samples (root, stem, mature stem, leaf, flower, and leaf sheath) and at two developmental stages (before and after flowering) in bamboo specimens obtained in three locations. The stability and suitability of the candidate reference genes were validated using the geNorm, NormFinder and BestKeeper programs. The results showed that TIP41 and NTB were suitable reference genes across all the tissues and at the different developmental stages examined in this study. While the expression of the NTB, TIP41 and UBQ were the mostly stable in different plant tissues samples, the expression of the TIP41, NTB and CAC were ranked the most stable in bamboo plants at various developmental stages. AP2-like gene was further assessed by using the reference genes TIP41 and NTB in comparison to ACT. Significant difference of the expression profile of AP2-like demonstrated the importance of choosing adequate reference genes in bamboo.

Conclusion

TIP41 and NTB were found to be homogeneously expressed and were adequate for normalization purposes, showing equivalent transcript levels in different samples. They are therefore the recommended reference genes for measuring gene expression in P. edulis.

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.

Identification of programmed cell death related genes in bamboo

The event of bamboo flowering and subsequent death of bamboo cells, a rare phenomenon is an interesting model to study gene expression/function in the context of the programmed cell death (PCD) in plant. To identify genes involved in autolytic cell death in bamboo (Bambusa arundinacea/Bambusa bambos Voss), a suppressive subtractive cDNA hybridization (SSH) was performed between cDNA isolated from control (healthy), as driver and test internodal tissue (45days after setting of seeds), as tester. In-silico data revealed that 82% of total ESTs (231) were non-significant (unidentified proteins) while remaining ESTs were classified as protein with known/predicted function/s. Among these, net distribution and differential expression patterns of 11 important B. arundinacea PCD specific ESTs were studied using RNA slot-blot, qRT-PCR and semi-quantitative RT. In-situ localization of mRNA-transcripts for selected bamboo PCD-specific ESTs namely V2Ba48 (Aldehyde dehydrogenase 2) and V2Ba19 (Glycogen phosphorylase) were detected using digoxigenin-labeled corresponding anti-sense RNA probes employing Confocal Laser Scanning Microscope (CLSM). Differential expression-kinetics of the aforementioned genes were confirmed during the progress of PCD after setting of seeds. Global appearance of V2Ba48, V2Ba19, V2Ba95 (Ubiquitin thioesterase) and V2Ba89 (Nebulin isoform 2) genes were identified in monocot (Oryza sativa) and dicots (Arabidopsis thaliana and Nicotiana tabacum). This is the first report on systematic analysis of genes involved in death of bamboo cells that may provide critical information regarding key metabolic/regulatory genes involved in plant PCD.