애기장대 생물적 및 비생물적 스트레스에 관여하는 유전자들의 기능에 대한 연구

DoctorPlants are continuously exposed to environmental stresses that slow their growth. Stresses can be abiotic (e.g., drought, salinity, extreme temperatures, heavy metals), or biotic (e.g., pathogen attack, competition from other plants). Due to anthropogenic activities, heavy-metal contamination of soil has become a major threat for organisms including plants. Moreover, the distribution of these metals in soil is highly heterogeneous. To withstand the toxicity and heterogeneity of soil that contains heavy metals, plants modify their root architecture to avoid unfavorable conditions and to grow towards favorable conditions. However, the transcription factors responsible for this root avoidance of heavy metals are not well characterized. In this study, I identified a GLABRA1 ENHANCER BINDING PROTEIN (GeBP) family transcription factor which is an important factor for the avoidance of heavy metal stress in roots and allows the reallocation of resources for root growth to less-affected area. I performed a large-scale screening of Arabidopsis thaliana CRES-T (Chimeric REpressor gene Silencing Technology) lines for altered tolerance to cadmium (Cd) and found that CRES-T lines of a transcription factor belonging to GeBP family were altered in Cd tolerance. I named this transcription factor GeBP-LIKE 4 (GPL4) and report that it functions as a toxic metal-avoidance factor. When exposed to toxic levels of Cd, transgenic plants with suppressed GPL4 expression (CRES-T and RNAi) had larger root apical meristems and grew better than the wild type, whereas plants that overexpressed GPL4 had the opposite phenotype. In a split root assay in which only half of the medium or soil contained toxic levels of Cd, wild-type plants exhibited increased root biomass specifically in the low-Cd side. By contrast, the roots of GPL4 CRES-T and RNAi plants grew equally well in both the Cd and control sides and the shoots accumulated more Cd than did the wild type. Upon exposure to Cd, GPL4 regulated the transcription of genes related to the oxidative stress response. Expression of these genes increased levels of reactive oxygen species in roots and thereby inhibited root growth in Cd-containing medium. These results suggest that, upon exposure to toxic metal stress, GPL4 mediates change of root growth towards non-contaminated regions. Biotic stress can occur due to damage caused by pathogens such as viruses, bacteria and fungi. To withstand and ward off pathogens effectively, plants have developed diverse defense systems, one of which relies on chemicals, called secondary metabolites. However, accumulation of these chemicals within the plant cell can be toxic to plants themselves, so an appropriate transport system is required to achieve timely and accurate transport of these double edged weapons. ABC transporters are well known for the transport of chemicals in several plant species, specifically ABCG-type full-size ABC transporters are important during chemical defense. To identify the ABCG transporter for pathogen defense in Arabidopsis, I screened abcg knock-out mutants pool for sclareol (a defense molecule) sensitivity and found out that abcg34 knockout mutants were hypersensitive compared to wild type. Complementation of abcg34 mutant with ABCG34 reversed the hypersensitive phenotype. Furthermore, ABCG34 is induced in response to methyl jasmonate and necrotrophic pathogens and localized at the peripheral plasma membrane of epidermal cells both in shoot and roots. abcg34 knockout mutants exhibited hypersensitivity to necrotrophic pathogens. The surface camalexin, a major phytoalexin in Arabidopsis, was significantly reduced in the abcg34 mutants compared to wild type and overexpression of ABCG34 enhanced secretion of surface camalexin and pathogen resistance. Moreover, abcg34 exhibited increased sensitivity to exogenously applied camalexin. Heterologous expression of ABCG34 in Tobacco BY2 cells conferred resistance to camalexin supplied in the medium compared to empty vector expressing cells. These data suggest that ABCG34 is an important factor in pathogen defense

Arabidopsis ABCG34 contributes to defense against necrotrophic pathogens by mediating the secretion of camalexin

Plant pathogens cause huge yield losses. Plant defense often depends on toxic secondary metabolites that inhibit pathogen growth. Because most secondary metabolites are also toxic to the plant, specific transporters are needed to deliver them to the pathogens. To identify the transporters that function in plant defense, we screened Arabidopsis thaliana mutants of full-size ABCG transporters for hypersensitivity to sclareol, an antifungal compound. We found that atabcg34 mutants were hypersensitive to sclareol and to the necrotrophic fungi Alternaria brassicicola and Botrytis cinereaAtABCG34 expression was induced by Abrassicicola inoculation as well as by methyl-jasmonate, a defense-related phytohormone, and AtABCG34 was polarly localized at the external face of the plasma membrane of epidermal cells of leaves and roots. atabcg34 mutants secreted less camalexin, a major phytoalexin in Athaliana, whereas plants overexpressing AtABCG34 secreted more camalexin to the leaf surface and were more resistant to the pathogen. When treated with exogenous camalexin, atabcg34 mutants exhibited hypersensitivity, whereas BY2 cells expressing AtABCG34 exhibited improved resistance. Analyses of natural Arabidopsis accessions revealed that AtABCG34 contributes to the disease resistance in naturally occurring genetic variants, albeit to a small extent. Together, our data suggest that AtABCG34 mediates camalexin secretion to the leaf surface and thereby prevents Abrassicicola infection

Root avoidance of toxic metals requires the GeBP-LIKE 4 transcription factor in Arabidopsis thaliana

Plants reorganize their root architecture to avoid growth into unfavorable regions of the rhizosphere. In a screen based on chimeric repressor gene-silencing technology, we identified the Arabidopsis thaliana GeBP-LIKE 4 (GPL4) transcription factor as an inhibitor of root growth that is induced rapidly in root tips in response to cadmium (Cd). We tested the hypothesis that GPL4 functions in the root avoidance of Cd by analyzing root proliferation in split medium, in which only half of the medium contained toxic concentrations of Cd. The wild-type (WT) plants exhibited root avoidance by inhibiting root growth in the Cd side but increasing root biomass in the control side. By contrast, GPL4-suppression lines exhibited nearly comparable root growth in the Cd and control sides and accumulated more Cd in the shoots than did the WT. GPL4 suppression also altered the root avoidance of toxic concentrations of other essential metals, modulated the expression of many genes related to oxidative stress, and consistently decreased reactive oxygen species concentrations. We suggest that GPL4 inhibits the growth of roots exposed to toxic metals by modulating reactive oxygen species concentrations, thereby allowing roots to colonize noncontaminated regions of the rhizosphere

Association of methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms with coronary artery disease (CAD) in a North Indian population

This is an Open Access Article. It is published by Cogent OA under the Creative Commons Attribution 4.0 International Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/There is significant variation in reported associations of the MTHFR C677T (rs1801133) and A1298C (rs1801131) polymorphisms and coronary artery disease (CAD) in different global populations. This study aims to identify any individual or combined associations between the 1298 and 677 loci of MTHFR and CAD in a North Indian population. A total of 159 patients and 166 controls were genotyped using validated TaqMan assays. Odds ratio analysis identified associations at crude level and multiple logistic regression controlled for confounding variables. Linkage disequilibrium between the loci was assessed along with haplotype association analysis. At the C677T locus, homozygosity of the T allele identified a significantly protective association (OR = 0.38, CI: 0.24–0.60). For the A1298C locus the AC genotype had a protective effect in codominant model (OR = 0.53, CI: 0.32–0.85) and CC genotype showed a susceptible association in recessive model when controlled for age, sex and lipids (OR = 2.70, CI: 1.27–5.77). This study identified that, independently, both heterozygous genotypes show a protective association with CAD. In addition the CC genotype of A1298C in recessive model was a susceptible genotype. The combined associations of MTHFR are protective (primarily due to the effects of C677T locus) suggesting an interaction between the loci and their associations with CAD within this sample

Non-intrinsic ATP-binding cassette proteins ABCI19, ABCI20 and ABCI21 modulate cytokinin response at the endoplasmic reticulum in Arabidopsis thaliana

Key messageThe non-intrinsic ABC proteins ABCI20 and ABCI21 are induced by light under HY5 regulation, localize to the ER, and ameliorate cytokinin-driven growth inhibition in young Arabidopsis thaliana seedlings. The plant ATP-binding cassette (ABC) I subfamily (ABCIs) comprises heterogeneous proteins containing any of the domains found in other ABC proteins. Some ABCIs are known to function in basic metabolism and stress responses, but many remain functionally uncharacterized. ABCI19, ABCI20, and ABCI21 of Arabidopsis thaliana cluster together in a phylogenetic tree, and are suggested to be targets of the transcription factor ELONGATED HYPOCOTYL 5 (HY5). Here, we reveal that these three ABCIs are involved in modulating cytokinin responses during early seedling development. The ABCI19, ABCI20 and ABCI21 promoters harbor HY5-binding motifs, and ABCI20 and ABCI21 expression was induced by light in a HY5-dependent manner. abci19 abci20 abci21 triple and abci20 abci21 double knockout mutants were hypersensitive to cytokinin in seedling growth retardation assays, but did not show phenotypic differences from the wild type in either control medium or auxin-, ABA-, GA-, ACC- or BR-containing media. ABCI19, ABCI20, and ABCI21 were expressed in young seedlings and the three proteins interacted with each other, forming a large protein complex at the endoplasmic reticulum (ER) membrane. These results suggest that ABCI19, ABCI20, and ABCI21 fine-tune the cytokinin response at the ER under the control of HY5 at the young seedling stage

Plant ABC transporters enable many unique aspects of a terrestrial plant's lifestyle

Terrestrial plants have two to four times more ATP-binding cassette (ABC) transporter genes than other organisms, including their ancestral microalgae. Recent studies found that plants harboring mutations in these transporters exhibit dramatic phenotypes, many of which are related to developmental processes and functions necessary for life on dry land. These results suggest that ABC transporters multiplied during evolution and assumed novel functions that allowed plants to adapt to terrestrial environmental conditions. Examining the literature on plant ABC transporters from this viewpoint led us to propose that diverse ABC transporters enabled many unique and essential aspects of a terrestrial plant's lifestyle, by transporting various compounds across specific membranes of the plant

Differential expression of genes influencing mitotic processes in cord blood mononuclear cells after a pre-conceptional micronutrient-based randomised controlled trial: Pune Rural Intervention in Young Adolescents (PRIYA)

In The Pune Maternal Nutrition Study, vitamin B12 deficiency was seen in 65% of pregnant women, folate deficiency was rare. Maternal total homocysteine concentrations were inversely associated with offspring birthweight, and low vitamin B12 and high folate concentrations predicted higher offspring adiposity and insulin resistance. These findings guided a nested pre-conceptional randomised controlled trial 'Pune Rural Intervention in Young Adolescents'. The interventions included: (1) vitamin B12+multi-micronutrients as per the United Nations International Multiple Micronutrient Antenatal Preparation, and proteins (B12+MMN), (2) vitamin B12 (B12 alone), and (3) placebo. Intervention improved maternal pre-conceptional and in-pregnancy micronutrient nutrition. Gene expression analysis in cord blood mononuclear cells in 88 pregnancies revealed 75 differentially expressed genes between the B12+MMN and placebo groups. The enriched biological processes included G2/M phase transition, chromosome segregation, and nuclear division. Enriched pathways included, mitotic spindle checkpoint and DNA damage response while enriched human phenotypes were sloping forehead and decreased head circumference. Fructose-bisphosphatase 2 (FBP2) and Cell Division Cycle Associated 2 (CDCA2) genes were under-expressed in the B12 alone group. The latter, involved in chromosome segregation was under-expressed in both intervention groups. Based on the role of B-complex vitamins in the synthesis of nucleotides and S-adenosyl methionine, and the roles of vitamins A and D on gene expression, we propose that the multi-micronutrient intervention epigenetically affected cell cycle dynamics. Neonates in the B12+MMN group had the highest ponderal index. Follow-up studies will reveal if the intervention and the altered biological processes influence offspring diabesity.</p