A Turnip Mosaic Virus Determinant of Systemic Necrosis in Nicotiana benthamiana and a Novel Resistance-Breaking Determinant in Chinese Cabbage Identified from Chimeric Infectious Clones

Infectious clones of Korean turnip mosaic virus (TuMV) isolates KIH1 and HJY1 share 88.1% genomic nucleotides and 96.4% polyprotein amino acid identity, and they induce systemic necrosis or mild mosaic, respectively, in Nicotiana benthamiana. Chimeric constructs between these isolates exchanged the 5', central, and 3' domains of KIH1 (K) and HJY1 (H), where the order of the letters indicates the origin of these domains. KIH1 and chimeras KHH and KKH induced systemic necrosis, whereas HJY1 and chimeras HHK, HKK, and HKH induced mild symptoms, indicating the determinant of necrosis to be within the 5' 3.9 kb of KIH1; amino acid identities of the included P1, Helper component protease, P3, 6K1, and cylindrical inclusion N-terminal domain were 90.06, 98.91, 93.80, 100, and 100%, respectively. Expression of P1 or P3 from a potato virus X vector yielded symptom differences only between P3 of KIH1 and HJY1, implicating a role for P3 in necrosis in N. benthamiana. Chimera KKH infected Brassica rapa var. pekinensis 'Norang', which was resistant to both KIH1 and HJY1, indicating that two separate TuMV determinants are required to overcome the resistance. Ability of diverse TuMV isolates, chimeras, and recombinants to overcome resistance in breeding lines may allow identification of novel resistance genes.

Genetic and tissue-specific RNA-sequencing analysis of self-compatible mutant TSC28 in Brassica rapa L. toward identification of a novel self-incompatibility factor

Self-incompatibility (SI) is a sophisticated system for pollen selectivity to prevent pollination by genetically identical pollen. In Brassica, it is genetically controlled by a single, highly polymorphic S-locus, and the male and female S-determinant factors have been identified as S-locus protein 11 (SP11)/S-locus cysteine-rich protein (SCR) and S-locus receptor kinase (SRK), respectively. However, the overall molecular system and identity of factors in the downstream cascade of the SI reaction remain unclear. Previously, we identified a self-compatible B. rapa mutant line, TSC28, which has a disruption in an unidentified novel factor of the SI signaling cascade. Here, in a genetic analysis of TSC28, using an F₂ population from a cross with the reference B. rapa SI line Chiifu-401, the causal gene was mapped to a genetic region of DNA containing markers BrSA64 and ACMP297 in B. rapa chromosome A1. By fine mapping using an F₂ population of 1,034 plants, it was narrowed down to a genetic region between DNA markers ACMP297 and BrgMS4028, with physical length approximately 1.01 Mbp. In this genomic region, 113 genes are known to be located and, among these, we identified 55 genes that were expressed in the papilla cells. These are candidates for the gene responsible for the disruption of SI in TSC28. This list of candidate genes will contribute to the discovery of a novel downstream factor in the SP11-SRK signaling cascade in the Brassica SI system.

Five Newly Collected Turnip Mosaic Virus (TuMV) Isolates from Jeju Island, Korea are Closely Related to Previously Reported Korean TuMV Isolates but Show Distinctive Symptom Development

For several years, temperatures in the Korean peninsula have gradually increased due to climate change, resulting in a changing environment for growth of crops and vegetables. An associated consequence is that emerging species of insect vector have caused increased viral transmission. In Jeju Island, Korea, occurrences of viral disease have increased. Here, we report characterization of five newly collected turnip mosaic virus (TuMV) isolates named KBJ1, KBJ2, KBJ3, KBJ4 and KBJ5 from a survey on Jeju Island in 2017. Full-length cDNAs of each isolate were cloned into the pJY vector downstream of cauliflower mosaic virus 35S and bacteriophage T7 RNA polymerase promoters. Their fulllength sequences share 98.9-99.9% nucleotide sequence identity and were most closely related to previously reported Korean TuMV isolates. All isolates belonged to the BR group and infected both Chinese cabbage and radish. Four isolates induced very mild symptoms in Nicotiana benthamiana but KBJ5 induced a hypersensitive response. Symptom differences may result from three amino acid differences uniquely present in KBJ5; Gly(382)Asp, Ile(891)Val, and Lys(2522)Glu in P1, P3, and NIb, respectively.

A single nucleotide change in the overlapping MP and CP reading frames results in differences in symptoms caused by two isolates of Youcai mosaic virus

Two isolates of Youcai mosaic virus (YoMV) were obtained, and their full-length genomic sequences were determined. Full-length infectious cDNA clones of each isolate were generated in which the viral sequence was under the control of dual T7 and 35S promoters for both in vitro transcript production and agro-infiltration. Comparison of the predicted amino acid sequences of the encoded proteins revealed only four differences between the isolates: three in the RNA-dependent RNA polymerase (RdRp) (V383I and M492I in the 125-kDa protein and T1245M in the 182-kDa protein); and one in the overlapping region of the movement protein (MP) and coat protein (CP) genes, affecting only the N-terminal domain of CP (CP M17T). One of the isolates caused severe symptoms in Nicotiana benthamiana plants, while the other caused only mild symptoms. In order to identify the amino acid residues associated with symptom severity, chimeric constructs were generated by combining parts of the two infectious YoMV clones, and the symptoms in infected plants were compared to those induced by the parental isolates. This allowed us to conclude that the M17T substitution in the N-terminal domain of CP was responsible for the difference in symptom severity. The M17T variation was found to be unique among characterized YoMV isolates. A difference in potential post-translational modification resulting from the presence of a predicted casein kinase II phosphorylation site only in the CP of isolate HK2 may be responsible for the symptom differences.

Abstract LB-200: A pan-cancer analysis of stage-dependent gene expression program

Cancer cells undergo diverse gene expression alterations according to their development and progression due to the accumulation of mutations. Understanding these phenomena not only provide us an insight into the underlying mechanisms of cancer development, but also offer useful information on the prediction of patient's prognosis. For some cancer types, previous studies attempted to identify key genes that change with the development of cancer. However, identification of cancer stage-dependent gene expression dysregulations based on pan-cancer dataset have not been addressed. Here, based on gene expression profiles and clinical data from 20 major cancer types and ~6,000 individual patients, we identified both gene expression programs that specifically change from each cancer-type and across all cancer types. Based on the pan-cancer analysis, we found that cell cycle and p53 dependent pathways are the most commonly dysregulated pathways across all cancer types according to cancer development. Next, we investigated whether the identified the stage-dependent gene expression programs from the pan-cancer analysis also hold from each cancer-type analysis. Interestingly, we identified that only about half cancer types also showed consistent gene expression alterations. These results suggest that although most cancer share common dysregulation mechanisms as cancer progress, also show that some cancer type have quite unique cancer development programs depending on the cancer type.

Keywords: stage-dependent gene expression, systems biology, PANCANCER

Citation Format: Man-Sun Kim, Dongsan Kim, Jeong-Rae Kim, Yong Pyo Lim. A pan-cancer analysis of stage-dependent gene expression program [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-200.

Isolation and characterization of fusarium wilt resistance gene analogs in radish

The resistance gene analog (RGA)-based marker strategy is an effective supplement for current marker reservoir of radish disease-resistance breeding. In this study, we identified RGAs based on the conserved nucleotide-binding site (NBS) and S-receptor-like kinase (SRLK) domains. A total of 68 NBS-RGAs and 46 SRLK-RGAs were isolated from two FW-resistant radish inbred lines, B2 and YR31, and one susceptible line, YR15. A BLASTx search revealed that the NBS-RGAs contained six conserved motifs (i.e., P loop, RNBS-A, Kinase-2, RNBS-B, RNBS-C, and GLPL) and the SRLK-RGAs, contained two conserved motifs (i.e., G-type lectin and PAN-AP). A phylogenetic analysis indicated that the NBS-RGAs could be separated into two classes (i.e., toll/interleukin receptor and coiled-coil types), with six subgroups, and the SRLK-RGAs were divided into three subgroups. Moreover, we designed RGA-specific markers from data-mining approach in radish databases. Based on marker analysis, 24 radish inbred lines were clustered into five main groups with a similarity index of 0.44 and showing genetic diversity with resistance variation in those radish inbred lines. The development of RGA-specific primers would be valuable for marker-assisted selection during the breeding of disease-resistant radish cultivars.

Biochemical Analysis of the Role of Leucine-Rich Repeat Receptor-Like Kinases and the Carboxy-Terminus of Receptor Kinases in Regulating Kinase Activity in Arabidopsis thaliana and Brassica oleracea

Protein post-translational modification by phosphorylation is essential for the activity and stability of proteins in higher plants and underlies their responses to diverse stimuli. There are more than 300 leucine-rich repeat receptor-like kinases (LRR-RLKs), a major group of receptor-like kinases (RLKs) that plays an important role in growth, development, and biotic stress responses in higher plants. To analyze auto- and transphosphorylation patterns and kinase activities in vitro, 43 full-length complementary DNA (cDNA) sequences were cloned from genes encoding LRR-RLKs. Autophosphorylation activity was found in the cytoplasmic domains (CDs) of 18 LRR-RLKs; 13 of these LRR-RLKs with autophosphorylation activity showed transphosphorylation in Escherichia coli. BRI1-Associated Receptor Kinase (BAK1), which is critically involved in the brassinosteroid and plant innate immunity signal transduction pathways, showed strong auto- and transphosphorylation with multi-specific kinase activity within 2 h of induction of Brassica oleraceae BAK1-CD (BoBAK1-CD) in E. coli; moreover, the carboxy-terminus of LRR-RLKs regulated phosphorylation and kinase activity in Arabidopsis thaliana and vegetative crops.

An Alcohol Dehydrogenase Gene from Synechocystis sp. Confers Salt Tolerance in Transgenic Tobacco

Synechocystis salt-responsive gene 1 (sysr1) was engineered for expression in higher plants, and gene construction was stably incorporated into tobacco plants. We investigated the role of Sysr1 [a member of the alcohol dehydrogenase (ADH) superfamily] by examining the salt tolerance of sysr1-overexpressing (sysr1-OX) tobacco plants using quantitative real-time polymerase chain reactions, gas chromatography-mass spectrometry, and bioassays. The sysr1-OX plants exhibited considerably increased ADH activity and tolerance to salt stress conditions. Additionally, the expression levels of several stress-responsive genes were upregulated. Moreover, airborne signals from salt-stressed sysr1-OX plants triggered salinity tolerance in neighboring wild-type (WT) plants. Therefore, Sysr1 enhanced the interconversion of aldehydes to alcohols, and this occurrence might affect the quality of green leaf volatiles (GLVs) in sysr1-OX plants. Actually, the Z-3-hexenol level was approximately twofold higher in sysr1-OX plants than in WT plants within 1-2 h of wounding. Furthermore, analyses of WT plants treated with vaporized GLVs indicated that Z-3-hexenol was a stronger inducer of stress-related gene expression and salt tolerance than E-2-hexenal. The results of the study suggested that increased C6 alcohol (Z-3-hexenol) induced the expression of resistance genes, thereby enhancing salt tolerance of transgenic plants. Our results revealed a role for ADH in salinity stress responses, and the results provided a genetic engineering strategy that could improve the salt tolerance of crops.

Ethanol Extract of Brassica rapa ssp. pekinensis Suppresses Tumor Necrosis Factor-α-Induced Inflammatory Response in Human Umbilical Vein Endothelial Cells

Brassica rapa L. ssp. pekinensis, commonly known as Chinese cabbage, is a cruciferous vegetable traditionally consumed in east Asia. Although its habitual consumption could account for the low incidence of chronic vascular inflammation, the therapeutic and protective potential of phytochemicals derived from Chinese cabbage has been poorly studied. In this study, we identified the phenolic compounds, kaempferol and quercetin, from the ethanol extract of Chinese cabbage (EtCC). We show for the first time that EtCC contains effective phytochemicals that suppress tumor necrosis factor (TNF)-α-induced inflammatory response in human umbilical vein endothelial cells. The EtCC inhibited TNF-α-induced monocyte adhesion to endothelial cells in a dose-dependent manner. The antiadhesive activity of EtCC directly correlated with downregulation of expression and transcription of vascular cell adhesion molecule-1 (VCAM-1). It was caused by an Nrf-2-dependent mechanism, leading to activation of antioxidant responsive element-driven promoter. Taken together, these results suggest that EtCC inhibits the expression of TNF-α-induced adhesion molecules through the indirect transcriptional modulation of VCAM-1 in endothelial cells. In conclusion, regular consumption of vegetables containing dietary phytochemicals might be a potential therapeutic strategy to protect against various stresses, to prevent several pathological conditions, and to treat chronic vascular inflammation, such as atherosclerosis.

Integrated analysis of leaf morphological and color traits in different populations of Chinese cabbage (Brassica rapa ssp. pekinensis)

QTLs and candidate gene markers associated with leaf morphological and color traits were identified in two immortalized populations of Brassica rapa, which will provide genetic information for marker-assisted breeding. Brassica rapa is an important leafy vegetable consumed worldwide and morphology is a key character for its breeding. To enhance genetic control, quantitative trait loci (QTLs) for leaf color and plant architecture were identified using two immortalized populations with replications of 2 and 4 years. Overall, 158 and 80 QTLs associated with 23 and 14 traits were detected in the DH and RIL populations, respectively. Among them, 23 common robust-QTLs belonging to 12 traits were detected in common loci over the replications. Through comparative analysis, five crucifer genetic blocks corresponding to morphology trait (R, J&U, F and E) and color trait (F, E) were identified in three major linkage groups (A2, A3 and A7). These might be key conserved genomic regions involved with the respective traits. Through synteny analysis with Arabidopsis, 64 candidate genes involved in chlorophyll biosynthesis, cell proliferation and elongation were co-localized within QTL intervals. Among them, SCO3, ABI3, FLU, HCF153, HEMB1, CAB3 were mapped within QTLs for leaf color; and CYCD3;1, CYCB2;4, AN3, ULT1 and ANT were co-localized in QTL regions for leaf size. These robust QTLs and their candidate genes provide useful information for further research into leaf architecture with crop breeding.

Duplicated pollen-pistil recognition loci control intraspecific unilateral incompatibility in Brassica rapa

In plants, cell-cell recognition is a crucial step in the selection of optimal pairs of gametes to achieve successful propagation of progeny. Flowering plants have evolved various genetic mechanisms, mediated by cell-cell recognition, to enable their pistils to reject self-pollen, thus preventing inbreeding and the consequent reduced fitness of progeny (self-incompatibility, SI), and to reject foreign pollen from other species, thus maintaining species identity (interspecific incompatibility)¹. In the genus Brassica, the SI system is regulated by an S-haplotype-specific interaction between a stigma-expressed female receptor (S receptor kinase, SRK) and a tapetum cell-expressed male ligand (S locus protein 11, SP11), encoded by their respective polymorphic genes at the S locus^2-6. However, the molecular mechanism for recognition of foreign pollen, leading to reproductive incompatibility, has not yet been identified. Here, we show that recognition between a novel pair of proteins, a pistil receptor SUI1 (STIGMATIC UNILATERAL INCOMPATIBILITY 1) and a pollen ligand PUI1 (POLLEN UNILATERAL INCOMPATIBILITY 1), triggers unilateral reproductive incompatibility between plants of two geographically distant self-incompatible Brassica rapa lines, even though crosses would be predicted to be compatible based on the S haplotypes of pollen and stigma. Interestingly, SUI1 and PUI1 are similar to the SI genes, SRK and SP11, respectively, and are maintained as cryptic incompatibility genes in these two populations. The duplication of the SRK and SP11 followed by reciprocal loss in different populations would provide a molecular mechanism of the emergence of a reproductive barrier in allopatry.

Identification and characterization of the leaf specific networks of inner and rosette leaves in Brassica rapa

Inner and rosette leaves of Chinese cabbage (Brassica rapa) have different characteristics in terms of nutritional value, appearance, taste, color and texture. Many researchers have utilized differentially expressed genes for exploring the difference between inner and rosette leaves of Brassica rapa. The functional characteristics of a gene, however, is determined by complex interactions between genes. Hence, a noble network approach is required for elucidating such functional difference that is not captured by gene expression profiles alone. In this study, we measured gene expression in the standard cabbage genome by RNA-Sequencing and constructed rosette and inner leaf networks based on the gene expression profiles. Furthermore, we compared the topological and functional characteristics of these networks. We found significant functional difference between the rosette and inner leaf networks. Specifically, we found that the genes in the rosette leaf network were associated with homeostasis and response to external stimuli whereas the genes in the inner leaf network were mainly related to the glutamine biosynthesis processes and developmental processes with hormones. Overall, the network approach provides an insight into the functional difference of the two leaves.

Natural variation in CIRCADIAN CLOCK ASSOCIATED 1 is associated with flowering time in Brassica rapa

Flowering time is a very important agronomic trait and the development of molecular markers associated with this trait can facilitate crop breeding. CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), a core oscillator component of circadian rhythms that affect metabolic pathways in plants, has been implicated in flowering time control in species of Brassica. CCA1 gene sequences from three Brassica rapa inbred lines, showing either early flowering or late flowering phenotypes, were analyzed and a high level of sequence variation was identified, especially within the fourth intron. Using this information, three PCR primer sets were designed and tested using various inbred lines of B. rapa. The usage of InDel markers was further validated by evaluation of flowering time and high resolution melting (HRM) analysis. Both methods, PCR and HRM, validated the use of newly developed markers. Additional sequence analyses of Brassica plants with diploid (AA, BB, or CC) and allotetraploid genomes further confirmed a large number of sequence polymorphisms in the CCA1 gene, including insertions/deletions in the fourth intron. Our results demonstrated that sequence variations in CCA1 can be used to develop valuable trait-related molecular markers for Brassica crop breeding.

Genome-Wide Analysis and Characterization of Aux/IAA Family Genes in Brassica rapa

Auxins are the key players in plant growth development involving leaf formation, phototropism, root, fruit and embryo development. Auxin/Indole-3-Acetic Acid (Aux/IAA) are early auxin response genes noted as transcriptional repressors in plant auxin signaling. However, many studies focus on Aux/ARF gene families and much less is known about the Aux/IAA gene family in Brassica rapa (B. rapa). Here we performed a comprehensive genome-wide analysis and identified 55 Aux/IAA genes in B. rapa using four conserved motifs of Aux/IAA family (PF02309). Chromosomal mapping of the B. rapa Aux/IAA (BrIAA) genes facilitated understanding cluster rearrangement of the crucifer building blocks in the genome. Phylogenetic analysis of BrIAA with Arabidopsis thaliana, Oryza sativa and Zea mays identified 51 sister pairs including 15 same species (BrIAA-BrIAA) and 36 cross species (BrIAA-AtIAA) IAA genes. Among the 55 BrIAA genes, expression of 43 and 45 genes were verified using Genebank B. rapa ESTs and in home developed microarray data from mature leaves of Chiifu and RcBr lines. Despite their huge morphological difference, tissue specific expression analysis of BrIAA genes between the parental lines Chiifu and RcBr showed that the genes followed a similar pattern of expression during leaf development and a different pattern during bud, flower and siliqua development stages. The response of the BrIAA genes to abiotic and auxin stress at different time intervals revealed their involvement in stress response. Single Nucleotide Polymorphisms between IAA genes of reference genome Chiifu and RcBr were focused and identified. Our study examines the scope of conservation and divergence of Aux/IAA genes and their structures in B. rapa. Analyzing the expression and structural variation between two parental lines will significantly contribute to functional genomics of Brassica crops and we belive our study would provide a foundation in understanding the Aux/IAA genes in B. rapa.

Quantitative Trait Loci for Morphological Traits and their Association with Functional Genes in Raphanus sativus

Identification of quantitative trait loci (QTLs) governing morphologically important traits enables to comprehend their potential genetic mechanisms in the genetic breeding program. In this study, we used 210 F2 populations derived from a cross between two radish inbred lines (Raphanus sativus) "835" and "B2," including 258 SSR markers were used to detect QTLs for 11 morphological traits that related to whole plant, leaf, and root yield in 3 years of replicated field test. Total 55 QTLs were detected which were distributed on each linkage group of the Raphanus genome. Individual QTLs accounted for 2.69-12.6 of the LOD value, and 0.82-16.25% of phenotypic variation. Several genomic regions have multiple traits that clustered together, suggested the existence of pleiotropy linkage. Synteny analysis of the QTL regions with A. thaliana genome selected orthologous genes in radish. InDels and SNPs in the parental lines were detected in those regions by Illumina genome sequence. Five identified candidate gene-based markers were validated by co-mapping with underlying QTLs affecting different traits. Semi-quantitative reverse transcriptase PCR analysis showed the different expression levels of these five genes in parental lines. In addition, comparative QTL analysis with B. rapa revealed six common QTL regions and four key major evolutionarily conserved crucifer blocks (J, U, R, and W) harboring QTL for morphological traits. The QTL positions identified in this study will provide a valuable resource for identifying more functional genes when whole radish genome sequence is released. Candidate genes identified in this study that co-localized in QTL regions are expected to facilitate in radish breeding programs.

Anatomic Characteristics Associated with Head Splitting in Cabbage (Brassica oleracea var. capitata L.)

Cabbage belonging to Brassicaceae family is one of the most important vegetables cultivated worldwide. The economically important part of cabbage crop is head, formed by leaves which may be of splitting and non-splitting types. Cabbage varieties showing head splitting causes huge loss to the farmers and therefore finding the molecular and structural basis of splitting types would be helpful to breeders. To determine which anatomical characteristics were related to head-splitting in cabbage, we analyzed two contrasting cabbage lines and their offspring using a field emission scanning electron microscope. The inbred line “747” is an early head-splitting type, while the inbred line “748” is a head-splitting-resistant type. The petiole cells of “747” seems to be larger than those of “748” at maturity; however, there was no significant difference in petiole cell size at both pre-heading and maturity stages. The lower epidermis cells of “747” were larger than those of “748” at the pre-heading and maturity stages. “747” had thinner epidermis cell wall than “748” at maturity stage, however, there was no difference of the epidermis cell wall thickness in the two lines at the pre-heading stage. The head-splitting plants in the F₁ and F₂ population inherited the larger cell size and thinner cell walls of epidermis cells in the petiole. In the petiole cell walls of “747” and the F₁ and F₂ plants that formed splitting heads, the cellulose microfibrils were loose and had separated from each other. These findings verified that anomalous cellulose microfibrils, larger cell size and thinner-walled epidermis cells are important genetic factors that make cabbage heads prone to splitting.

Accumulation of Phenylpropanoids by White, Blue, and Red Light Irradiation and Their Organ-Specific Distribution in Chinese Cabbage (Brassica rapa ssp. pekinensis)

This study investigated optimum light conditions for enhancing phenylpropanoid biosynthesis and the distribution of phenylpropanoids in organs of Chinese cabbage (Brassica rapa ssp. pekinensis). Blue light caused a high accumulation of most phenolic compounds, including p-hydroxybenzoic acid, ferulic acid, quercetin, and kaempferol, at 12 days after irradiation (DAI). This increase was coincident with a noticeable increase in expression levels of BrF3H, BrF3'H, BrFLS, and BrDFR. Red light led to the highest ferulic acid content at 12 DAI and to elevated expression of the corresponding genes during the early stages of irradiation. White light induced the highest accumulation of kaempferol and increased expression of BrPAL and BrDFR at 9 DAI. The phenylpropanoid content analysis in different organs revealed organ-specific accumulation of p-hydroxybenzoic acid, quercetin, and kaempferol. These results demonstrate that blue light is effective at increasing phenylpropanoid biosynthesis in Chinese cabbage, with leaves and flowers representing the most suitable organs for the production of specific phenylpropanoids.

L-Dopa production and antioxidant activity in Hybanthus enneaspermus (L.) F. Muell regeneration

Hybanthus enneaspermus is an ethanobotanical plant extensively used in Indian traditional medicine. Quick and efficient in vitro mass propagation of this plant species was established for commercial utilization from leaf and node explants using various concentrations and combinations of plant growth regulators and polyamines. The maximum number of multiple shoots per leaf explant (40 shoots) was achieved on MS medium supplemented with 20 mg/l spermidine in combination with 4 mg/l BA+1.5 mg/l IAA after 8 weeks of culture. The elongated shoots were rooted (16 roots/shoot) on MS medium with the best concentration of IBA (1.5 mg/l) and in combination with 20 mg/l putrescine after 5 weeks of culture. The plants were successfully acclimatized (98 %) in the sand: soil: vermiculite mixture (1:1:1 v/v/v) in the greenhouse. An increased antioxidant activity was recorded in vitro regenerated shoots when compared to in vitro-induced roots. L-Dopa content was recorded higher in leaves (8.31 mg/g DW) followed by stem (6.22 mg/g DW) and root (3.22 mg/g DW) of leaf-derived plants than the field-grown parent plant after 5 weeks. By adopting this protocol, the regenerated-plants could be used for drug production and pharmacology work with as an alternative to field-grown plants.

Expression of important pathway genes involved in withanolides biosynthesis in hairy root culture of Withania somnifera upon treatment with Gracilaria edulis and Sargassum wightii

The investigation of seaweeds, Gracilaria edulis and Sargassum wightii extracts was carried out for the estimation of growth characteristics and major withanolides production in hairy root culture of Withania somnifera. The extract of G. edulis (50%) in MS liquid basal medium enabled maximum production of dry biomass (5.46 g DW) and withanolides contents (withanolide A 5.23 mg/g DW; withaferin A 2.24 mg/g DW and withanone 4.83 mg/g DW) in hairy roots after 40 days of culture with 48 h contact time. The obtained withanolides contents were significantly higher (2.32-fold-2.66-fold) in hairy root culture when compared to the control. RT PCR analysis of important pathway genes such as SE, SS, HMGR and FPPS exhibited substantial higher expression upon the seaweed extracts treatment in hairy root culture. This experiment would paw a platform for withanolides production in hairy root culture with the influence of sea weed extracts for pharmaceutical companies in the future.

Quantitative trait loci mapping of partial resistance to Diamondback moth in cabbage (Brassica oleracea L)

The resistance to Diamondback moth insect in cabbage is governed by many minor loci in quantitative nature, and at least four genetic loci should be incorporated in marker-assisted breeding program for developing partially resistant DBM cabbage cultivars. The Diamondback moth (DBM), Plutella xylostella (L.), is the most destructive insect infesting cruciferous plants worldwide. Earlier studies have reported that the glossy leaves of cabbage are associated with resistance to this insect. However, until now, genetics of DBM resistance has not been studied in detail, and no QTL/gene mapping for this trait has been reported. In this paper, we report quantitative trait loci (QTL) mapping of DBM-resistant trait using 188 randomly selected segregating F 3 population derived from crossing a partially DBM-resistant glossy leaf cabbage (748) with a susceptible smooth cabbage line (747). Quantitative trait loci mapping using phenotypic data of four consecutive years (2008, 2009, 2010, and 2011) on DBM insect infestation detected a total of eight QTL on five linkage groups suggesting that DBM resistance is a quantitative in nature. Of these QTL, four QTL, i.e., qDbm 1 on LG1, qDbm5 and qDbm6 on LG7, and qDbm8 on LG9, were detected in different tests and years. The QTL, qDbm6 on LG7, was consecutively detected over 3 years. Tightly linked molecular markers have been developed for qDbm8 QTL on LG9 which could be used in marker-assisted breeding program. Our research demonstrated that for desired DBM resistance cultivar breeding, those four genetic loci have to be taken into consideration. Furthermore, the comparative study revealed that DBM resistance QTL is conserved between close relative model plant Arabidopsis thaliana and Brassica oleracea genome.

Transgenic alfalfa plants expressing the sweetpotato Orange gene exhibit enhanced abiotic stress tolerance

Alfalfa (Medicago sativa L.), a perennial forage crop with high nutritional content, is widely distributed in various environments worldwide. We recently demonstrated that the sweetpotato Orange gene (IbOr) is involved in increasing carotenoid accumulation and enhancing resistance to multiple abiotic stresses. In this study, in an effort to improve the nutritional quality and environmental stress tolerance of alfalfa, we transferred the IbOr gene into alfalfa (cv. Xinjiang Daye) under the control of an oxidative stress-inducible peroxidase (SWPA2) promoter through Agrobacterium tumefaciens-mediated transformation. Among the 11 transgenic alfalfa lines (referred to as SOR plants), three lines (SOR2, SOR3, and SOR8) selected based on their IbOr transcript levels were examined for their tolerance to methyl viologen (MV)-induced oxidative stress in a leaf disc assay. The SOR plants exhibited less damage in response to MV-mediated oxidative stress and salt stress than non-transgenic plants. The SOR plants also exhibited enhanced tolerance to drought stress, along with higher total carotenoid levels. The results suggest that SOR alfalfa plants would be useful as forage crops with improved nutritional value and increased tolerance to multiple abiotic stresses, which would enhance the development of sustainable agriculture on marginal lands.

Computer vision syndrome: a study of knowledge and practices in university students

INTRODUCTION

Computer vision syndrome (CVS) is a condition in which a person experiences one or more of eye symptoms as a result of prolonged working on a computer.

OBJECTIVES

To determine the prevalence of CVS symptoms, knowledge and practices of computer use in students studying in different universities in Malaysia, and to evaluate the association of various factors in computer use with the occurrence of symptoms.

MATERIAL AND METHODS

In a cross sectional, questionnaire survey study, data was collected in college students regarding the demography, use of spectacles, duration of daily continuous use of computer, symptoms of CVS, preventive measures taken to reduce the symptoms, use of radiation filter on the computer screen, and lighting in the room.

RESULTS

A total of 795 students, aged between 18 and 25 years, from five universities in Malaysia were surveyed. The prevalence of symptoms of CVS (one or more) was found to be 89.9%; the most disturbing symptom was headache (19.7%) followed by eye strain (16.4%). Students who used computer for more than 2 hours per day experienced significantly more symptoms of CVS (p=0.0001). Looking at far objects in-between the work was significantly (p=0.0008) associated with less frequency of CVS symptoms. The use of radiation filter on the screen (p=0.6777) did not help in reducing the CVS symptoms.

CONCLUSION

Ninety percent of university students in Malaysia experienced symptoms related to CVS, which was seen more often in those who used computer for more than 2 hours continuously per day.

Construction of chromosome segment substitution lines enables QTL mapping for flowering and morphological traits in Brassica rapa

Chromosome segment substitution lines (CSSLs) represent a powerful method for precise quantitative trait loci (QTL) detection of complex agronomical traits in plants. In this study, we used a marker-assisted backcrossing strategy to develop a population consisting of 63 CSSLs, derived from backcrossing of the F1 generated from a cross between two Brassica rapa subspecies: "Chiifu" (ssp. pekinensis), the Brassica "A" genome-represented line used as the donor, and "49caixin" (ssp. parachinensis), a non-heading cultivar used as the recipient. The 63 CSSLs covered 87.95% of the B. rapa genome. Among them, 39 lines carried a single segment; 15 lines, two segments; and nine lines, three or more segments of the donor parent chromosomes. To verify the potential advantage of these CSSL lines, we used them to locate QTL for six morphology-related traits. A total of 58 QTL were located on eight chromosomes for all six traits: 17 for flowering time, 14 each for bolting time and plant height, six for plant diameter, two for leaf width, and five for flowering stalk diameter. Co-localized QTL were mainly distributed on eight genomic regions in A01, A02, A05, A06, A08, A09, and A10, present in the corresponding CSSLs. Moreover, new chromosomal fragments that harbored QTL were identified using the findings of previous studies. The CSSL population constructed in our study paves the way for fine mapping and cloning of candidate genes involved in late bolting, flowering, and plant architecture-related traits in B. rapa. Furthermore, it has great potential for future marker-aided gene/QTL pyramiding of other interesting traits in B. rapa breeding.

Overexpression of codA gene confers enhanced tolerance to abiotic stresses in alfalfa

We generated transgenic alfalfa plants (Medicago sativa L. cv. Xinjiang Daye) expressing a bacterial codA gene in chloroplasts under the control of the SWPA2 promoter (referred to as SC plants) and evaluated the plants under various abiotic stress conditions. Three transgenic plants (SC7, SC8, and SC9) were selected for further characterization based on the strong expression levels of codA in response to methylviologen (MV)-mediated oxidative stress. SC plants showed enhanced tolerance to NaCl and drought stress on the whole plant level due to induced expression of codA. When plants were subjected to 250 mM NaCl treatment for 2 weeks, SC7 and SC8 plants maintained higher chlorophyll contents and lower malondialdehyde levels than non-transgenic (NT) plants. Under drought stress conditions, all SC plants showed enhanced tolerance to drought stress through maintaining high relative water contents and increased levels of glycinebetaine and proline compared to NT plants. Under normal conditions, SC plants exhibited increased growth due to increased expression of auxin-related IAA genes compared to NT plants. These results suggest that the SC plants generated in this study will be useful for enhanced biomass production on global marginal lands, such as high salinity and arid lands, yielding a sustainable agricultural product.

Transgenic alfalfa plants expressing AtNDPK2 exhibit increased growth and tolerance to abiotic stresses

In this study, we generated and evaluated transgenic alfalfa plants (Medicago sativa L. cv. Xinjiang Daye) expressing the Arabidopsis nucleoside diphosphate kinase 2 (AtNDPK2) gene under the control of the oxidative stress-inducible SWPA2 promoter (referred to as SN plants) to develop plants with enhanced tolerance to various abiotic stresses. We selected two SN plants (SN4 and SN7) according to the expression levels of AtNDPK2 and the enzyme activity of NDPK in response to methyl viologen (MV)-mediated oxidative stress treatment using leaf discs for further characterization. SN plants showed enhanced tolerance to high temperature, NaCl, and drought stress on the whole-plant level. When the plants were subjected to high temperature treatment (42 °C for 24 h), the non-transgenic (NT) plants were severely wilted, whereas the SN plants were not affected because they maintained high relative water and chlorophyll contents. The SN plants also showed significantly higher tolerance to 250 mM NaCl and water stress treatment than the NT plants. In addition, the SN plants exhibited better plant growth through increased expression of auxin-related indole acetic acid (IAA) genes (MsIAA3, MsIAA5, MsIAA6, MsIAA7, and MsIAA16) under normal growth conditions compared to NT plants. The results suggest that induced overexpression of AtNDPK2 in alfalfa will be useful for increasing biomass production under various abiotic stress conditions.