Insertional mutagenesis of Brachypodium distachyon using the Tnt1 retrotransposable element

Medicago truncatula resources to study legume biology and symbiotic nitrogen fixation

Medicago truncatula is a chosen model for legumes towards deciphering fundamental legume biology, especially symbiotic nitrogen fixation. Current genomic resources for M. truncatula include a completed whole genome sequence information for R108 and Jemalong A17 accessions along with the sparse draft genome sequences for other 226 M. truncatula accessions. These genomic resources are complemented by the availability of mutant resources such as retrotransposon (Tnt1) insertion mutants in R108 and fast neutron bombardment (FNB) mutants in A17. In addition, several M. truncatula databases such as small secreted peptides (SSPs) database, transporter protein database, gene expression atlas, proteomic atlas, and metabolite atlas are available to the research community. This review describes these resources and provide information regarding how to access these resources.

Tracing Mobile DNAs: From Molecular to Population Scales

Transposable elements (TEs, transposons) are mobile DNAs that are prevalent in most eukaryotic genomes. In plants, their mobility has vastly contributed to genetic diversity which is essential for adaptive changes and evolution of a species. Such mobile nature of transposon has been also actively exploited in plant science research by generating genetic mutants in non-model plant systems. On the other hand, transposon mobilization can bring about detrimental effects to host genomes and they are therefore mostly silenced by the epigenetic mechanisms. TEs have been studied as major silencing targets and acted a main feature in the remarkable growth of the plant epigenetics field. Despite the importance of transposon in plant biology and biotechnology, their mobilization and the underlying mechanisms are largely left unanswered. This is mainly because of the sequence repetitiveness of transposons, which makes their detection and analyses difficult and complicated. Recently, some attempts have been made to develop new experimental methods detecting active transposons and their mobilization behavior. These techniques reveal TE mobility in various levels, including the molecular, cellular, organismal and population scales. In this review, we will highlight the novel technical approaches in the study of mobile genetic elements and discuss how these techniques impacted on the advancement of transposon research and broadened our understanding of plant genome plasticity.

Construction of a Full-Length cDNA Over-Expressing Library to Identify Valuable Genes from Populus tomentosa

Poplar wood is the main source of renewable biomass energy worldwide, and is also considered to be a model system for studying woody plants. The Full-length cDNA Over-eXpressing (FOX) gene hunting system is an effective method for generating gain-of-function mutants. Large numbers of novel genes have successfully been identified from many herbaceous plants according to the phenotype of gain-of-function mutants under normal or abiotic stress conditions using this system. However, the system has not been used for functional gene identification with high-throughput mutant screening in woody plants. In this study, we constructed a FOX library from the Chinese white poplar, Populus tomentosa. The poplar cDNA library was constructed into the plant expression vector pEarleyGate101 and further transformed into Arabidopsis thaliana (thale cress). We collected 1749 T1 transgenic plants identified by PCR. Of these, 593 single PCR bands from different transgenic lines were randomly selected for sequencing, and 402 diverse sequences of poplar genes were isolated. Most of these genes were involved in photosynthesis, environmental adaptation, and ribosome biogenesis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotation. We characterized in detail two mutant lines carrying PtoCPCa or PtoWRKY13 cDNA insertions. Phenotypic characterization showed that overexpression of these genes in A. thaliana affected trichome development or secondary cell wall (SCW) deposition, respectively. Together, the Populus-FOX-Arabidopsis library generated in our experiments will be helpful for efficient discovery of novel genes in poplar.