Overexpression of heat shock protein gene PfHSP21.4 in Arabidopsis thaliana enhances heat tolerance

Nuclear-encoded chloroplast small heat shock proteins (Cp-sHSPs) play important roles in plant stress tolerance due to their abundance and diversity. Their functions in Primula under heat treatment are poorly characterized. Here, expression analysis showed that the Primula Cp-sHSP gene, PfHSP21.4, was highly induced by heat stress in all vegetative and generative tissues in addition to constitutive expression in certain development stages. PfHSP21.4 was introduced into Arabidopsis, and its function was analysed in transgenic plants. Under heat stress, the PfHSP21.4 transgenic plants showed increased heat tolerance as shown by preservation of hypocotyl elongation, membrane integrity, chlorophyll content and photosystem II activity (Fv/Fm), increased seedling survival and increase in proline content. Alleviation of oxidative damage was associated with increased activity of superoxide dismutase and peroxidase. In addition, the induced expression of HSP101, HSP70, ascorbate peroxidase and Δ1-pyrroline-5-carboxylate synthase under heat stress was more pronounced in transgenic plants than in wild-type plants. These results support the positive role of PfHSP21.4 in response to heat stress in plants.     

The plasma membrane-bound phospholipase Ddelta enhances freezing tolerance in Arabidopsis thaliana

Freezing injury is a major environmental limitation on the productivity and geographical distribution of plants. Here we show that freezing tolerance can be manipulated in Arabidopsis thaliana by genetic alteration of the gene encoding phospholipase Ddelta (PLDdelta), which is involved in membrane lipid hydrolysis and cell signaling. Genetic knockout of the plasma membrane-associated PLDdelta rendered A. thaliana plants more sensitive to freezing, whereas overexpression of PLDdelta increased freezing tolerance. Lipid profiling revealed that PLDdelta contributed approximately 20% of the phosphatidic acid produced in wild-type plants during freezing, and overexpression of PLDdelta increased the production of phosphatidic acid species. The PLDdelta alterations did not affect the expression of the cold-regulated genes COR47 or COR78 or alter cold-induced increases in proline or soluble sugars, suggesting that the PLD pathway is a unique determinant of the response to freezing and may present opportunities for improving plant freezing tolerance.     

Putrescine accumulation in Arabidopsis thaliana transgenic lines enhances tolerance to dehydration and freezing stress

Polyamines have been globally associated to plant responses to abiotic stress. Particularly, putrescine has been related to a better response to cold and dehydration stresses. It is known that this polyamine is involved in cold tolerance, since Arabidopsis thaliana plants mutated in the key enzyme responsible for putrescine synthesis (arginine decarboxilase, ADC; EC 4.1.1.19) are more sensitive than the wild type to this stress. Although it is speculated that the overexpression of ADC genes may confer tolerance, this is hampered by pleiotropic effects arising from the constitutive expression of enzymes from the polyamine metabolism. Here, we present our work using A. thaliana transgenic plants harboring the ADC gene from oat under the control of a stress-inducible promoter (pRD29A) instead of a constitutive promoter. The transgenic lines presented in this work were more resistant to both cold and dehydration stresses, associated with a concomitant increment in endogenous putrescine levels under stress. Furthermore, the increment in putrescine upon cold treatment correlates with the induction of known stress-responsive genes, and suggests that putrescine may be directly or indirectly involved in ABA metabolism and gene expression.Key words: cold acclimation, dehydration, putrescine, polyamines, stress     

Transformation with a gene for myo-inositol O-methyltransferase enhances the cold tolerance of Arabidopsis thaliana

In this study, we report a function of myo-inositol-O-methyltransferase (Imt1) in response to low temperature stress using transgenic Arabidopsis thaliana. Imt1 gene was constructed identical to the Imt1 gene from a halophyte Mesembryanthemum crystallinum. After cold stress, the Imt1 transgenic plants exhibited stronger growth than the wild type plants. The elevated cold tolerance of the Imt1 over-expressing plants was confirmed by the lower electrolyte leakage and accumulation of malondialdehyde, but higher proline and soluble sugar contents in transgenic than wild type plants.     

Arabidopsis thaliana PDX1.2 is critical for embryo development and heat shock tolerance

Main conclusion

PDX1.2 is expressed in the basal part of the globular-stage embryo, and plays critical roles in development, hypocotyl elongation, and stress response.

Abstract

The Arabidopsis thaliana PDX1.2 protein belongs to a small family of three members. While PDX1.1 and PDX1.3 have been extensively described and are well established to function in vitamin B₆ biosynthesis, the biological role of PDX1.2 still remains elusive. Here, we show that PDX1.2 is expressed early in embryo development, and that heat shock treatment causes a strong up-regulation of the gene. Using a combined genetic approach of T-DNA insertion lines and expression of artificial micro RNAs, we can show that PDX1.2 is critically required for embryo development, and for normal hypocotyl elongation. Plants with reduced PDX1.2 expression also display reduced primary root growth after heat shock treatments. The work overall provides a set of important new findings that give greater insights into the developmental role of PDX1.2 in plants.     

The expression of BrMDHAR gene in chloroplasts and mitochondria enhances tolerance to freezing stress in Arabidopsis thaliana

In chloroplasts and mitochondria, antioxidant mechanisms include the ascorbate-glutathione cycle, and monodehydroascorbate reductase (MDHAR) is important for regeneration of ascorbate (AsA) from monodehydroascorbate (MDHA). To improve detoxification of reactive oxygen species (ROS), we established a construct of the MDHAR gene from Brassica rapa fused to the targeting signal peptides of Pisum sativum glutathione reductase (GR), which was controlled by a stress-inducible SWPA2 promoter, and introduced this expression system into Arabidopsis thaliana. Transgenic (TG) plants overexpressing BrMDHAR targeted to chloroplasts and mitochondria through signal peptides showed an elevated MDHAR activity and an increased ratio of AsA to dehydroascorbate (DHA) when compared to wild-type (WT) plants under a freezing stress. These led to increased photosynthetic parameters, redox homeostasis, and biomass in TG plants when compared to the WT plants. Our results suggest that the overexpression of the BrMDHAR gene targeted to chloroplasts and mitochondria conferred an enhanced tolerance against the freezing stress, and a stress adaptation of dual-targeted BrMDHAR was better than that of single BrMDHAR.     

拟南芥MT-II过量表达提高抗旱性(英文)

富含巯基的植物II型金属硫蛋白(MT)对植物抵抗重金属胁迫具有重要作用,其中一个可能机制是金属硫蛋白可能猝灭重金属引起的氧化胁迫。利用转MT-II基因和野生型拟南芥(Arabidopsis thaliana)植株来对比研究MT在胁迫过程中通过清除氧自由基,特别是H2O2而对植物抗旱性的影响。研究表明,转基因型拟南芥能有效维持体内氧化—还原势,减少MDA的产生,从而缓解干旱胁迫引起的伤害,提高抗旱性。     

Expression of the broccoli catalase gene (BoCAT) enhances heat tolerance in transgenic Arabidopsis

The objective of this study was to transfer catalase gene (CAT1 and CAT2) complementary (c)DNAs under the control of a ubiquitin promoter into Arabidopsis via Agrobacterium-mediated transformation. A real-time polymerase chain reaction analysis demonstrated that both the BoCAT1 and BoCAT2 genes were overexpressed in transgenic Arabidopsis thaliana (At). The activity of CAT in the AtCAT2-2 transgenic line was 6-fold higher than that of the non-transgenic plant under heat stress, and the CAT amount in the AtCAT2-2 line also highly accumulated according to a Western blot analysis. Compared to non-transgenic Arabidopsis plants, a lower level of heat-induced H₂O₂ accumulation was detected by diaminobenzidine staining in leaves of transgenic plants with a high level of CAT activity, indicating that overexpression of BoCAT in Arabidopsis could enhance the heat tolerance by eliminating H₂O₂. This is the first report suggesting that CAT-encoding gene expression in Arabidopsis is regulated by heat stress.     

Methyl-coenzyme M reductase-dependent endogenous methane enhances plant tolerance against abiotic stress and alters ABA sensitivity in Arabidopsis thaliana

Plant Molecular Biology - Our study firstly elaborated the underlying mechanism of endogenous CH4-induced abiotic tolerance, along with an alteration of ABA sensitivity by mimicking the endogenous...     

Costs and benefits of cold tolerance in transgenic Arabidopsis thaliana

Cold tolerance in plants is an ecologically important trait that has been under intensive study for basic and applied reasons. Determining the fitness benefits and costs of cold tolerance has previously been difficult because cold tolerance is normally an induced trait that is not expressed in warm environments. The recent creation of transgenic plants constitutively expressing cold tolerance genes enables the investigation of the fitness consequences of cold tolerance in multiple temperature environments. We studied three genes from the CBF (C-repeat/dehydration responsive element binding factor) cold tolerance pathway, CBF1, 2 and 3, in Arabidopsis thaliana to test for benefits and costs of constitutive cold tolerance. We used multiple insertion lines for each transgene and grew the lines in cold and control conditions. Costs of cold tolerance, as determined by fruit number, varied by individual transgene. CBF2 and 3 overexpressers showed costs of cold tolerance, and no fitness benefits, in both environments. CBF1 overexpressing plants showed no fitness cost of cold tolerance in the control environment and showed a marginal fitness benefit in the cold environment. These results suggest that constitutive expression of traits that are normally induced in response to environmental stress will not always lead to costs in the absence of that stress, and that the ecological risks of CBF transgene escape should be assessed prior to their use in commercial agriculture.