Plant thioredoxins (Trxs) participate in two redox systems found in different cellular compartments: the NADP-Trx system (NTS) in the cytosol and mitochondria and the ferredoxin-Trx system (FTS) in the chloroplast, where they function as redox regulators by regulating the activity of various target enzymes. The identities of the master regulators that maintain cellular homeostasis and modulate timed development through redox regulating systems have remained completely unknown. Here, we show that proteins consisting of a single cystathionine b-synthase (CBS) domain pair stabilize cellular redox homeostasis and modulate plant development via regulation of Trx systems by sensing changes in adenosine-containing ligands. We identified two CBS domain-containing proteins in Arabidopsis thaliana, CBSX1 and CBSX2, which are localized to the chloroplast, where they activate all four Trxs in the FTS. CBSX3 was found to regulate mitochondrial Trx members in the NTS. CBSX1 directly regulates Trxs and thereby controls H 2 O 2 levels and regulates lignin polymerization in the anther endothecium. It also affects plant growth by regulating Calvin cycle enzymes, such as malate dehydrogenase, via homeostatic regulation of Trxs. Based on our findings, we suggest that the CBSX proteins (or a CBS pair) are ubiquitous redox regulators that regulate Trxs in the FTS and NTS to modulate development and maintain homeostasis under conditions that are threatening to the cell.
Caleosins or related sequences have been found in a wide range of higher plants. In Arabidopsis, seed-specific caleosins are viewed as oil-body (OB)-associated proteins that possess Ca(2+)-dependent peroxygenase activity and are involved in processes of lipid degradation. Recent experimental evidence suggests that one of the Arabidopsis non-seed caleosins, AtCLO3, is involved in controlling stomatal aperture during the drought response; the roles of the other caleosin-like proteins in Arabidopsis remain largely uncharacterized. We have demonstrated that a novel stress-responsive and OB-associated Ca(2+)-binding caleosin-like protein, AtCLO4, is expressed in non-seed tissues of Arabidopsis, including guard cells, and down-regulated following exposure to exogenous ABA and salt stress. At the seed germination stage, a loss-of-function mutant (atclo4) was hypersensitive to ABA, salt and mannitol stresses, whereas AtCLO4-overexpressing (Ox) lines were more hyposensitive to those stresses than the wild type. In adult stage, atclo4 mutant and AtCLO4-Ox plants showed enhanced and decreased drought tolerance, respectively. Following exposure to exogenous ABA, the expression of key ABA-dependent regulatory genes, such as ABF3 and ABF4, was up-regulated in the atclo4 mutant, while it was down-regulated in AtCLO4-Ox lines. Based on these results, we propose that the OB-associated Ca(2+)-binding AtCLO4 protein acts as a negative regulator of ABA responses in Arabidopsis.
Introgression lines derived from Oryza minuta and O. sativa subsp. japonica var. Junambyeo were crossed for a mapping of the population composed of 112 recombinant lines to identify putative QTLs against rice blast disease using the percentage of diseased leaf area. By using 148 Sequence Tagged Site (STS) and Single Sequence Repeat (SSR) markers, five QTLs on chromosomes 6, 7, 9 and 11 and seven epistatic QTLs were identified against two blast isolates (KI307 and KI209). Of them two QTLs (qKI307-2 and qKI209-3) shared a similar position on chromosome 11. O. minuta introgression contributed the resistance allele for all of these QTLs. Combined phenotypic variations by QTL and (E-QTL) accounted for 56.9% against KI307, and 53.4% against KI209. Each QTL could account for the resistance variation between 11 and 24.6%. The resistance from wild introgressions was attributable to a combination of QTLs and epistatic effects between different loci, capable of inducing hypersensitive reactions. Our findings are in support of the strategy of pyramiding major QTLs to develop improved rice varieties with durable broad spectrum resistance against the blast fungus.
Stormwater pollution is the untreated contaminated water that drains into natural waterways from land uses within an urban catchment. Several studies have demonstrated the deterioration of water quality in receiving bodies of water caused by stormwater runoff. The data have reported that urban runoff play primary roles in degrading water quality in adjacent aquatic systems. The accurate estimation of non-pollutant loads from urban runoff and the prediction of water quality in receiving waters are important. The objective of this paper is to assess the applicability of the watershed scale hydrologic and water quality simulation models SWMM and HSPF to simulate the hydrology of a small watershed in the Han River Basin. Monitoring was performed in small scale watersheds, which is homogeneous land use. The applicability of SWMM and HSPF model was examined for small watersheds using hourly monitoring data. The results of SWMM were reasonably reflected with observed data in small scale urban area. HSPF model was effective at specifying parameters related to runoff and water quality when using hourly monitoring data. The watershed models used in this study adequately simulated watershed characteristics and are recommended to support watershed management.
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