ABSTRACT
Abscisic acid (ABA) biosynthesis has been widely characterized in plants, whereas the effects of ABA biosynthesis on nitric oxide (NO) generation in osmotic stress are less well understood. In this study, Malus hupehensis Rehd. 9-cis-epoxycarotenoid dioxygenase gene (MhNCED3) which is the key gene in ABA biosynthesis was transformed into wild type (WT) and 129B08/nced3 mutant (AtNCED3 deficient), respectively, and two transgenic Arabidopsis lines were obtained. The transgenic Arabidopsis lines displayed higher endogenous ABA content, NO generation rate, AtNIA1 transcript level and nitrate reductase (NR) activity than WT and 129B08/nced3 mutant. Ectopic expression of MhNCED3 reduced the electrolyte leakage and relieved Arabidopsis damage caused by 20% PEG on the growth and development. The ABA content, NO generation rate, AtNIA1 expression and NR activity increased after 20% PEG treatment, importantly, their increases amplitude relative to that in control were higher in two transgenic lines. Additionally, during the treatment for the four genotype Arabidopsis, the time of ABA contents reaching the highest peak was earlier than the time of NO generation, AtNIA1 expression and NR activity reaching their highest peak. These results show that NCED gene indirectly induced endogenous NO generation in osmotic-stressed Arabidopsis partially contributing to the up-regulation of AtNIA1 expression and NR activity.
Subject(s)
Abscisic Acid/metabolism , Malus/metabolism , Nitric Oxide/biosynthesis , Arabidopsis/metabolism , Nitric Oxide/metabolism , Osmotic PressureABSTRACT
High Cl(-) concentrations in tissues can be toxic to crop plants and may lead to reduced growth rates and yields. 9-cis-epoxycarotenoid dioxygenase (NCED) is thought to be involved in the biosynthesis of abscisic acid (ABA), which is an important regulator of plant adaptive responses to stress. Here, the expression of MhNCED3 in Malus hupehensis Rehd. and the effects of MhNCED3 on plant tolerance to Cl(-) stress were explored. The results showed that MhNCED3 expression and ABA biosynthesis in M. hupehensis Rehd. were induced by Cl(-) stress. Ectopic expression of MhNCED3 in Arabidopsis complemented the phenotypic defects of the 129B08/nced3 mutant and enhanced WT tolerance to Cl(-) stress. The transgenic Arabidopsis showed improved growth and developmental status, increased ABA contents, and reduced transpiration rates and relative water content. Furthermore, ectopic expression of MhNCED3 decreased Cl(-) accumulation and oxidative damage, and up-regulated the expression levels of AtCLCc (chloride channel protein) and AtSLAH3 (slow anion channel 1 homolog 3) genes in Arabidopsis. These observations suggest that MhNCED3 has critical role in enhancing plant tolerance to Cl(-) stress by reducing Cl(-) accumulation.
Subject(s)
Adaptation, Physiological/genetics , Arabidopsis/genetics , Chlorides/metabolism , Dioxygenases/genetics , Genes, Plant , Malus/genetics , Plant Proteins/genetics , Stress, Physiological , Abscisic Acid/metabolism , Arabidopsis/growth & development , Arabidopsis/metabolism , Arabidopsis Proteins/genetics , Arabidopsis Proteins/metabolism , Chloride Channels/genetics , Chloride Channels/metabolism , Chlorides/adverse effects , Dioxygenases/metabolism , Gene Expression Regulation, Plant , Malus/enzymology , Membrane Proteins/genetics , Membrane Proteins/metabolism , Oxidative Stress/genetics , Plant Proteins/metabolism , Plant Transpiration/genetics , Plants, Genetically Modified/genetics , Plants, Genetically Modified/metabolism , Up-Regulation , Water/metabolismABSTRACT
This paper studied the fatty acid composition, reactive oxygen species (ROS), lipoxygenase (LOX) activity, and malondialdehyde (MDA) content in the leaves and roots of Malus hupehensis seedlings under effects of cadmium (Cd) stress. Noticeable changes were observed in the kinds and relative contents of fatty acids after treated with CdCl2 for 7-12 hours. The relative contents of unsaturated fatty acids in leaves and roots reached the maximum after treated for 7 hours, being 82. 82% and 72. 43% , respectively. The kinds of fatty acids in leaves increased from 11 to 14 after treated for 12 hours, while those in roots increased from 4 to 6 after treated for 17 hours. The O2* generation rate and the H2O2 content reached the maximum after treated for 3 and 7 hours, respectively, and the MDA content and LOX activity increased with treating time. Cd stress altered the fatty acid composition of Malus hupehensis via the inducement of reactive oxygen species and lipoxygenase, and induced lipid peroxidation, which was caused by both ROS and LOX within the first 12 hours of CdCl2 treatment and mainly by the increase of LOX activity since then.
Subject(s)
Cadmium/toxicity , Fatty Acids/metabolism , Lipid Peroxidation/drug effects , Malus/metabolism , Stress, Physiological , Fatty Acids/chemistry , Lipoxygenase/metabolism , Malus/chemistry , Malus/drug effects , Reactive Oxygen Species/metabolism , Soil Pollutants/toxicityABSTRACT
Taking the one-year cutting-seedlings of four grape cultivars (Kyoho, Muscat Hamburg, Long Yan, and Ze Xiang) as test materials, their root mitochondrial hydrogen peroxide (H2O2) content, membrane permeability transition pore (MPTP), membrane potential (Deltapsi), cytochrome C (Cyt c) content, and root activity were measured under effects of CdCl2. For all test grape cultivars, the root mitochondrial H2O2 content and MPTP increased, but the Deltapsi, Cyt c content, and root activity decreased after treated with 0.5 mmol CdCl2 x L(-1). The mitochondrial H2O2 content and Cyt c content were in the sequence of Kyoho > Ze Xiang > Muscat Hamburg > Long Yan, while the root activity, MPTP, and Deltapsi were in adverse, i.e., Long Yan > Muscat Hamburg > Ze Xiang > Kyoho. Among the test grape cultivars, the root activity of Kyoho was easier to be inhibited under Cd stress, while that of Long Yan was least affected by CdCl2.
