Taeyoung Lee

Genome sequence of mungbean and insights into evolution within Vigna species

Mungbean (Vigna radiata) is a fast-growing, warm-season legume crop that is primarily cultivated in developing countries of Asia. Here we construct a draft genome sequence of mungbean to facilitate genome research into the subgenus Ceratotropis, which includes several important dietary legumes in Asia, and to enable a better understanding of the evolution of leguminous species. Based on the de novo assembly of additional wild mungbean species, the divergence of what was eventually domesticated and the sampled wild mungbean species appears to have predated domestication. Moreover, the de novo assembly of a tetraploid Vigna species (V. reflexo-pilosa var. glabra) provides genomic evidence of a recent allopolyploid event. The species tree is constructed using de novo RNA-seq assemblies of 22 accessions of 18 Vigna species and protein sets of Glycine max. The present assembly of V. radiata var. radiata will facilitate genome research and accelerate molecular breeding of the subgenus Ceratotropis.

Draft genome sequence of adzuki bean, Vigna angularis

Adzuki bean (Vigna angularis var. angularis) is a dietary legume crop in East Asia. The presumed progenitor (Vigna angularis var. nipponensis) is widely found in East Asia, suggesting speciation and domestication in these temperate climate regions. Here, we report a draft genome sequence of adzuki bean. The genome assembly covers 75% of the estimated genome and was mapped to 11 pseudo-chromosomes. Gene prediction revealed 26,857 high confidence protein-coding genes evidenced by RNAseq of different tissues. Comparative gene expression analysis with V. radiata showed that the tissue specificity of orthologous genes was highly conserved. Additional re-sequencing of wild adzuki bean, V. angularis var. nipponensis, and V. nepalensis, was performed to analyze the variations between cultivated and wild adzuki bean. The determined divergence time of adzuki bean and the wild species predated archaeology-based domestication time. The present genome assembly will accelerate the genomics-assisted breeding of adzuki bean.

Mutation of Oryza sativa CORONATINE INSENSITIVE 1b (OsCOI1b) delays leaf senescence.

Jasmonic acid (JA) functions in plant development, including senescence and immunity. Arabidopsis thaliana CORONATINE INSENSITIVE 1 encodes a JA receptor and functions in the JA-responsive signaling pathway. The Arabidopsis genome harbors a single COI gene, but the rice (Oryza sativa) genome harbors three COI homologs, OsCOI1a, OsCOI1b, and OsCOI2. Thus, it remains unclear whether each OsCOI has distinct, additive, synergistic, or redundant functions in development. Here, we use the oscoi1b-1 knockout mutants to show that OsCOI1b mainly affects leaf senescence under senescence-promoting conditions. oscoi1b-1 mutants stayed green during dark-induced and natural senescence, with substantial retention of chlorophylls and photosynthetic capacity. Furthermore, several senescence-associated genes were downregulated in oscoi1b-1 mutants, including homologs of Arabidopsis thaliana ETHYLENE INSENSITIVE 3 and ORESARA 1, important regulators of leaf senescence. These results suggest that crosstalk between JA signaling and ethylene signaling affects leaf senescence. The Arabidopsis coi1-1 plants containing 35S:OsCOI1a or 35S:OsCOI1b rescued the delayed leaf senescence during dark incubation, suggesting that both OsCOI1a and OsCOI1b are required for promoting leaf senescence in rice. oscoi1b-1 mutants showed significant decreases in spikelet fertility and grain weight, leading to severe reduction of grain yield, indicating that OsCOI1-mediated JA signaling affects spikelet fertility and grain filling.

A parametric study on ethanol production from xylose byPichia stipitis

Characteristics of ethanol production by a xylose-fermenting yeast,Pichia stipitis Y-7124, were studied. The sugar consumption rate and specific growth rate were higher in the glucose-containing medium than in the xylose-containing medium. Specific activities of xylose reductase and xylitol dehydrogenase were higher in the medium with xylose than glucose, suggesting their induction by xylose. Maximum specific growth rate and ethanol yield were achieved at 30 g xylose/L concentration without formation of by-products such as xylitol and acetic acid whereas a maximum ethanol concentration was obtained at 130 g/L xylose. Adding a respiratory inhibitor, rotenone, increased a maximum ethanol concentration by 10% compared with the control experiment. In order to evaluate the pattern of ethanol inhibition on specific growth rate, a kinetic model based on Luong’s equations was applied. The relationship between ethanol concentration and specific growth rate was hyperbolic for glucose and parabolic for xylose. A maximum ethanol concentration at which cells did not grow was 33.6 g/L for glucose and 44.7 g/L for xylose.

Divergence of Flowering-Related Genes in Three Legume Species

We used a set of approximately 200 Arabidopsis thaliana (L.) Heynh. genes that are involved in the control of flowering time as a reference to identify orthologous (or homologous) counterparts of these genes in three legume species, that is, Lotus corniculatus L. var. japonicus Regel [syn. Lotus japonicus (Regel) K. Larsen], Medicago truncatula Gaertn. (barrel medic), and soybean [Glycine max (L.) Merr.]. A total of 96, 98, and 304 homologs of flowering genes were identified in L. corniculatus var. japonicus, M. truncatula, and G. max, respectively. Most of these genes were categorized into seven different flowering pathways, including photoperiod, vernalization, gibberellins, autonomous pathways, floral pathway integrators (FPIs), and floral meristem identity. Many key genes, including the FPI genes FT, SOC1, and LFY, are conserved in the legumes while CO, FRI, FLC, and FD were not. Eighteen genes were conserved as single copy genes in all three legume species, including GI, VRN2, COP1, and TSF. The chromosomal distribution of paralog‐rich genes revealed differences in the major evolutionary processes affecting flowering genes in legumes, including whole genome duplication in soybean, tandem duplication in M. truncatula, and ectopic duplication in L. corniculatus var. japonicus. High divergence was observed among the members of large gene families, most containing transcription factors, indicating the accumulation of gene copies and gene divergence during evolutionary adaptations to environmental changes.

Translational genomics for plant breeding with the genome sequence explosion

Summary The use of next‐generation sequencers and advanced genotyping technologies has propelled the field of plant genomics in model crops and plants and enhanced the discovery of hidden bridges between genotypes and phenotypes. The newly generated reference sequences of unstudied minor plants can be annotated by the knowledge of model plants via translational genomics approaches. Here, we reviewed the strategies of translational genomics and suggested perspectives on the current databases of genomic resources and the database structures of translated information on the new genome. As a draft picture of phenotypic annotation, translational genomics on newly sequenced plants will provide valuable assistance for breeders and researchers who are interested in genetic studies.

Development of lane change driver model for closed-loop simulation of the active safety system

In this paper, the integrated lane change driver model was proposed and used in simulations of closed loop simulation of the ESC system. Through the lane change experimental data, the drivers characteristics can be obtained and analyzed. By using the lane change steering input and the lane following steering input with weighting factors, lateral driver model is operated steering action to change or follow the lane. Also, simulation results of the proposed lane change model are compared with the experimental test data, and closed loop evaluation was conducted with ESC system. It has been shown that the proposed integrated lane change driver model can control a vehicle very similar to human manual driving in lane change situations and can represent a normal drivers driving motion. Consequently, the proposed driver model presented in this study can be used into a closed-loop simulation and development of the vehicles intelligent safety system.

Genome-wide comparative analysis of flowering genes between Arabidopsis and mungbean

Mungbean is one of the major crops grown in South, East and Southeast Asia because of a high quality of amino acid profile; however, its asynchronous flowering time makes difficult to harvest at a time. Synchronization of flowering time is important to reduce labor costs for harvesting. With the availability of next generation sequencing data of mungbean, we approached a strategy of comparative genomics to identify mungbean homologous counterpart of A. thaliana genes that are known to be involved in flowering pathways, followed by a comparative soybean quantitative trait loci (QTL) analysis of the putative mungbean flowering-related genes. Co-localization of mungbean QTL associated with days to first flower day (FLD) was also identified using the EST-SSR markers from a previous study. Additionally, based on the mungbean transcriptome data with a distinct flowering stage of R2, FPKM (Fragments Per Kilobase per Million mapped reads) expression analysis of all the genes found in paralogous synteny blocks was conducted to examine expression patterns of the genes that have undergone a whole genome duplication event. Our results indicate that the paralogous flowering genes along with other genes within a same synteny block have evolved together at the macro-synteny scale. This study provides insights into mungbean flowering genes, in which they can be used as tools in order to improve flowering synchronization and to increase yield.

Advanced Braking Algorithm for Robust Longitudinal Risk Management

This paper describes an advanced braking algorithm for robust longitudinal risk management to prevent or mitigate rear-end collisions. Since the proposed safety system works in conjunction with a human driver, the longitudinal safety system must be acceptable to the driver. The key to achieving this is to ensure that control signals are given at the appropriate time. In order to construct an suitable control system, a new longitudinal safety index was developed by using the time to collision and the warning index, which are well-known safety parameters in longitudinal safety control. The clearance and the relative velocity constitute essential signals for safety monitoring in longitudinal safety control. These measured sensor signals include the uncertainty in the measurement noise. To design a robust safety monitoring and control mode decision, information consisting of fusion of the measurement signals was obtained. In addition, an expected error range of the proposed safety index from the measurement noise can be defined from the covariance matrix of the Kalman filter and the deviation of the function of the new longitudinal safety index. The control performance of the proposed algorithm was evaluated by analysis of the simulation results. From this analysis, it can be concluded that the proposed advanced braking algorithm can substantially enhance the longitudinal safety and can guarantee a robust performance with respect to the sensor uncertainty.

Genome-wide DNA methylation profile in mungbean.

DNA methylation on cytosine residues is known to affect gene expression and is potentially responsible for the phenotypic variations among different crop cultivars. Here, we present the whole-genome DNA methylation profiles and assess the potential effects of single nucleotide polymorphisms (SNPs) for two mungbean cultivars, Sunhwanogdu (VC1973A) and Kyunggijaerae#5 (V2984). By measuring the DNA methylation levels in leaf tissue with the bisulfite sequencing (BSseq) approach, we show both the frequencies of the various types of DNA methylation and the distribution of weighted gene methylation levels. SNPs that cause nucleotide changes from/to CHH – where C is cytosine and H is any other nucleotide – were found to affect DNA methylation status in VC1973A and V2984. In order to better understand the correlation between gene expression and DNA methylation levels, we surveyed gene expression in leaf tissues of VC1973A and V2984 using RNAseq. Transcript expressions of paralogous genes were controlled by DNA methylation within the VC1973A genome. Moreover, genes that were differentially expressed between the two cultivars showed distinct DNA methylation patterns. Our mungbean genome-wide methylation profiles will be valuable resources for understanding the phenotypic variations between different cultivars, as well as for molecular breeding.