Stress In Transgenic Plants Research Articles

Repression of drought-induced cysteine-protease genes alters barley leaf structure and responses to abiotic and biotic stresses.

To survive under water deficiency, plants alter gene expression patterns, make structural and physiological adjustments, and optimize the use of water. Rapid degradation and turnover of proteins is required for effective nutrient recycling. Here, we examined the transcriptional responses of the C1A cysteine protease family to drought in barley and found that four genes were up-regulated in stressed plants. Knock-down lines for the protease-encoding genes HvPap-1 and HvPap-19 showed unexpected changes in leaf cuticle thickness and stomatal pore area. The efficiency of photosystem II and the total amount of proteins were almost unaltered in stressed transgenic plants while both parameters decreased in stressed wild-type plants. Although the patterns of proteolytic activities in the knock-down lines did not change, the amino acid accumulation increased in response to drought, concomitant with a higher ABA content. Whilst jasmonic acid (JA) and JA-Ile concentrations increased in stressed leaves of the wild-type and the HvPap-1 knock-down lines, their levels were lower in the HvPap-19 knock-down lines, suggesting the involvement of a specific hormone interaction in the process. Our data indicate that the changes in leaf cuticle thickness and stomatal pore area had advantageous effects on leaf defense against fungal infection and mite feeding mediated by Magnaporthe oryzae and Tetranychus urticae, respectively.

Overexpression of an aquaglyceroporin gene in Trichoderma harzianum affects stress tolerance, pathogen antagonism and Phaseolus vulgaris development

Aquaporins (AQPs) and aquaglyceroporins (AQGPs) are integral membrane proteins that mediate transport of water and a variety of low molecular weight solutes across biomembranes. We previously identified a gene encoding an AQGPs in Trichoderma harzianum that is up-regulated during biocontrol against Fusarium sp. and has biotechnological applications by improving tolerance to drought stress in transgenic plants. In this study, we report the cloning and overexpression of Thaqp in T. harzianum. Following transformation of T. harzianum via biobalistics, analysis of the resulting transformants showed that their tolerance to salt and osmotic stress was decreased when compared to the wild type. However, enhanced antagonistic activity against Fusarium oxysporum was observed in plate confrontation assays. Furthermore, evaluation of bean development after inoculation with transformants overexpressing Thaqp revealed plants with increased root volume, leaf area and dry weight. Our results underscore the strong potential of aquaglyceroporin in processes such as screening of microorganisms for biological control and molecular breeding of plants.

Cloning and characterization of SucNHX1, a novel vacular Na+/H+ antiporter from the halophyte Suaeda corniculata that enhances the saline-alkali tolerance in Arabidopsis by its overexpression

Vacuolar Na+/H+ antiporters play central roles in plant saline (NaCl) stress response. However, the functional characterizations of antiporters involved in plant saline-alkali (Na2CO3/NaHCO3) tolerance are limited. In this study, SucNHX1, a Na+/H+ antiporter gene was isolated from Suaeda corniculata, a halophyte native to the saline-alkali soil, and further studied in transgenic Arabidopsis thaliana. The SucNHX1 gene contains 2123 nucleotides with an open reading frame of 1665 nucleotides (GenBank accession number: DQ512716), encoding a polypeptide of 554 amino acids with a predicted molecular mass of 61.2 kDa. A northern blot analysis indicated that the enhanced mRNA accumulation of SucNHX1 was induced by sodium carbonate (Na2CO3) rather than by NaCl, polyethylene glycol or abscisic acid in S. corniculata seedlings. SucNHX1 was localized in membrane, nucleus and cytoplasm when it was transiently expressed in tobacco mesophyll cells. The expression of SucNHX1 in salt sensitive yeast mutant ΔenaΔnhx1 which lost of yeast vacuolar Na+/H+ antiporter ScNHX1 showed functional complementation. The transgenic Arabidopsis overexpressing SucNHX1 had higher Na2CO3 and NaCl tolerance levels than the wild-type plants. The expression patern of SucNHX1 under Na2CO3 and high NaCl stress in transgenic plants showed that SucNHX1 higher expressed under stress condition than normal control. The analysis of ion contents indicated that under Na2CO3 and NaCl conditions, there were more Na+ in the roots and higher K+/Na+ ratio in the leaves in the transgenic plants than in the wild-type plants. Thus, SucNHX1 may play a significant role in plant saline-alkali tolerance.

Overexpression of SbSKIP, A Pre-mRNA splicing factor from Sorghum bicolor, enhances root growth and drought tolerance in Petunia hybrida

Abstract Pre-mRNA splicing factors have been shown to have important roles in understanding the response of plants to various abiotic stresses. Different splicing factors might have different roles in plant stress responses. One splicer factor, skip (Sloan-Kettering retrovirus interacting protein), has been shown to play an important role in the tolerance of plants to various abiotic stresses although its mechanism of action is unknown. SbSKIP (Sorghum bicolor skip) encodes an RNA metabolism-related protein that could improve tobacco’s drought tolerance of tobacco. There is uncertainty how SbSKIP would act in other species and it effect on potential target genes. We found that overexpression of SbSKIP in Petunia hybrida could promote the growth of lateral roots and enhance drought tolerance. After withholding water for 14 d, SbSKIP plants grew better than WT (wild-type) plants; WT plants leaves were severely wilted and died, whereas transgenic plants were turgid after 17 d of drought treatment. Water stressed transgenic plants overexpressed SbSKIP, increased leaf proline synthesis and antioxidant defense enzyme activities, and decreased the accumulation of MDA. Furthermore, SbSKIP also regulated stress-induced gene expression under drought stress. These results suggest that overexpression of SbSKIP improves the tolerance of petunia to drought stress by enhancing antioxidant defense enzymes that decrease the content of cell membrane peroxidation, and by regulating the expression of stress-induced genes and the synthesis of proline.

Potential use of the DREB/ERF, MYB, NAC and WRKY transcription factors to improve abiotic and biotic stress in transgenic plants

Abiotic and biotic stresses adversely affect the growth and productivity of plants and constitute the major yield-limiting factor in agriculture. In recent years, several transcription factors (TF) have been identified that can function as switches to control the expression of potential stress-related genes. These transcription factors play crucial roles in governing transcriptional reprogramming during development in plant biological systems and are also capable of increasing the tolerance of plants to abiotic and biotic stresses. Thus, identifying and characterizing critical genes that are involved in plant stress responses are essential for the development of transgenic plants that exhibit enhanced stress tolerance. This review describes the DREB/ERF, MYB, NAC and WRKY TF and summarizes the studies that highlight their potential in engineering abiotic and biotic stress tolerance in transgenic plants.

Cloning, antibody production, expression and cellular localization of universal stress protein gene (USP1-GFP) in transgenic cotton

This study was aimed to clone the universal stress protein (GUSP1) gene isolated from Gossypium arboreum in E. coli expression vector pET30(a) and to raise the specific antibody in rabbit to devise a system that could be used for localization and expression of this gene under drought stress. The amplification of GUSP1 transgene revealed a fragment of 500 bp via PCR in genomic DNA of transgenic cotton plants and expression was confirmed through ELISA and Western blot by using the GUSP1 specific polyclonal antibodies. ELISA showed the expression of GUSP1 protein in roots, stem and leaves of transgenic plants at seedling, vegetative and mature plant developmental stages. Total protein isolated from drought stressed transgenic plants revealed a fragment of 47 kDa (GUSP1-GFP fusion protein) in Western blot which confirmed the expression of transgene. Confocal microscopy detected the GFP fluorescence as localization of GUSP1 in the midrib, guard cells of stomata, trichome and globular trichome of intact leaf of transgenic plants. The co-localization was observed within cytoplasm, palisade, spongy mesophyll, guard cells of stomata, vascular bundle, trichome and globular trichome of transgenic plants by using the GUSP1 specific primary antibodies and Alexa fluor conjugated secondary antibodies. This study of GUSP1 gene will advance the mechanism of abiotic stress tolerance in plants.

Post-translational modifications of Arabidopsis E3 SUMO ligase AtSIZ1 are controlled by environmental conditions.

Sumoylation regulates numerous cellular functions in plants as well as in other eukaryotic systems. However, the regulatory mechanisms controlling E3 small ubiquitin‐related modifier (SUMO) ligase are not well understood. Here, post‐translational modification of the Arabidopsis E3 SUMO ligase AtSIZ1 was shown to be specifically controlled by abiotic stresses. AtSIZ1 ubiquitination was induced by exposure to heat stress in transgenic plants overexpressing the E3 ubiquitin ligase COP1. In addition, AtSIZ1 ubiquitination was strongly enhanced in transgenic plants overexpressing SUMO isopeptidase ESD4 under heat stress. By contrast, drought stress induced sumoylation rather than ubiquitination of AtSIZ1 and sumoylated forms of AtSIZ1 accumulated in esd4 and cop1–4 mutants. Moreover, siz1 mutants were found to be tolerant to heat and drought stresses. Taken together, these results indicate that ubiquitination and sumoylation of AtSIZ1 in response to abiotic stresses depend on the activities of COP1 and ESD4 and that the activity and stability of AtSIZ1 can be specifically controlled by different abiotic stresses.

Diurnal and circadian regulation of salt tolerance in Arabidopsis

Most living organisms have a circadian clock, which coordinates their internal biological events with external environmental signals. Recent work showed that the Arabidopsis circadian clock regulates the plant’s responses to stresses such as drought, cold, pathogens, and wounding. However, the link between the circadian clock and the plant’s response to salinity, which retards plant growth and reduces crop yields, has not yet been investigated. In this study, we showed that tolerance to salinity stress is regulated by the diurnal cycle in Arabidopsis. The salt-induced expression of the salt- and drought-responsive transcription factor gene RD29A depends on the time of day and the transcription of the Na+/H+ antiporter gene SOS1 is under the control of the circadian clock. Furthermore, accumulation of SOS1 protein upon salt stress in transgenic plants that constitutively overexpress SOS1 (SOS1ox) appears to occur in a diurnal cycle. These findings suggest that during the salinity stress response, the expression of RD29A and SOS1 is modulated by diurnal cycles and the circadian clock, which allows the plant to anticipate and respond effectively to daytime transpiration-triggered dehydration, drought, and salinity stress.

Overexpression of the rice AKT1 potassium channel affects potassium nutrition and rice drought tolerance.

Potassium (K(+)) is the most important cationic nutrient for all living organisms and has roles in most aspects of plant physiology. To assess the impact of one of the main K(+) uptake components, the K(+) inward rectifying channel AKT1, we characterized both loss of function and overexpression of OsAKT1 in rice. In many conditions, AKT1 expression correlated with K(+) uptake and tissue K(+) levels. No salinity-related growth phenotype was observed for either loss or gain of function mutants. However, a correlation between AKT1 expression and root Na(+) when the external Na/K ratio was high suggests that there may be a role for AKT1 in Na(+) uptake in such conditions. In contrast to findings with Arabidopsis thaliana, we did not detect any change in growth of AKT1 loss of function mutants in the presence of NH4 (+) Nevertheless, NH4 (+)-dependent inhibition was detected during K(+) uptake assays in loss of function and wild type plants, depending on pre-growth conditions. The most prominent result of OsAKT1 overexpression was a reduction in sensitivity to osmotic/drought stress in transgenic plants: the data suggest that AKT1 overexpression improved rice osmotic and drought stress tolerance by increasing tissue levels of K(+), especially in the root.

Mulberry Transcription Factor MnDREB4A Confers Tolerance to Multiple Abiotic Stresses in Transgenic Tobacco.

The dehydration responsive element binding (DREB) transcription factors have been reported to be involved in stress responses. Most studies have focused on DREB genes in subgroups A-1 and A-2 in herbaceous plants, but there have been few reports on the functions of DREBs from the A-3–A-6 subgroups and in woody plants. Moreover, mulberry trees are ecologically and economically important perennial woody plants, but there has been little research on its stress physiology, biochemistry and molecular biology. In this study, a DREB gene from the mulberry tree, designated as MnDREB4A, classified into the A-4 subgroup by our previous study, was selected for further characterization. Our results showed that the MnDREB4A protein was localized to the nucleus where it activated transcription. The promoter of MnDREB4A can direct prominent expression downstream of the β-glucuronidase (GUS) gene under heat, cold, drought and salt stress, and GUS staining was deepest after 12 h of stress treatment. The MnDREB4A-overexpression transgenic tobacco showed the improved growth phenotype under untreated conditions, such as greener leaves, longer roots, and lower water loss and senescence rates. Overexpression of MnDREB4A in tobacco can significantly enhance tolerance to heat, cold, drought, and salt stresses in transgenic plants. The leaf discs and seedlings of transgenic plants reduced leaf wilting and senescence rates compared to the wild type plants under the different stress conditions. Further investigation showed that transgenic plants also had higher water contents and proline contents, and lower malondialdehyde contents under untreated condition and stress conditions. Our results indicate that the MnDREB4A protein plays an important role in plant stress tolerance.

An aquaporin gene from halophyte Sesuvium portulacastrum, SpAQP1, increases salt tolerance in transgenic tobacco.

SpAQP1 was strongly induced by salt in an ABA-independent way, promoted seed germination and root growth in transgenic tobaccos and increased salt tolerance by increasing the activities of antioxidative enzymes. Aquaporin (AQP) plays crucial roles in the responses of plant to abiotic stresses such as drought, salt and cold. Compared to glycophytes, halophytes often have excellent salt and drought tolerances. To uncover the molecular mechanism of halophyte Sesuvium portulacastrum tolerance to salt, in this study, an AQP gene, SpAQP1, from S. portulacastrum was isolated and characterized. The amino acid sequence of SpAQP1 shared high homology with that of plant plasma membrane intrinsic proteins (PIPs) and contained the distinct molecular features of PIPs. In the phylogenic tree, SpAQP1 was evidently classified as the PIP2 subfamily. SpAQP1 is expressed in roots, stems and leaves, and was significantly induced by NaCl treatment and inhibited by abscisic acid (ABA) treatment. When heterologously expressed in yeast and tobacco, SpAQP1 enhanced the salt tolerance of yeast strains and tobacco plants and promoted seed germination and root growth under salt stress in transgenic plants. The activity of antioxidative enzymes including superoxide dismutase, peroxidase and catalase was increased in transgenic plants overexpressing SpAQP1. Taken together, our studies suggested that SpAQP1 functioned in the responses of S. portulacastrum to salt stress and could increase salt tolerance by enhancing the antioxidative activity of plants.

Overexpression of lycopene ε-cyclase gene from lycium chinense confers tolerance to chilling stress in Arabidopsis thaliana

Lutein plays an important role in protecting the photosynthetic apparatus from photodamage and eliminating ROS to render normal physiological function of cells. As a rate-limiting step for lutein synthesis in plants, lycopene ε-cyclase catalyzes lycopene to δ-carotene. We cloned a lycopene ε-cyclase gene (Lcε-LYC) from Lycium chinense (L. chinense), a deciduous woody perennial halophyte growing in various environmental conditions. The Lcε-LYC gene has an ORF of 1569bp encoding a protein of 522 aa. The deduced amino acid sequence of Lcε-LYC gene has higher homology with LycEs in other plants, such as Nicotiana tabacum and Solanum tuberosum. When L. chinense was exposed to chilling stress, relative expression of Lcε-LYC increased. To study the protective role of Lcε-LYC against chilling stress, we overexpressed the Lcε-LYC gene in Arabidopsis thaliana. Lcε-LYC overexpression led to an increase of lutein accumulation in transgenic A. thaliana, and the content of lutein decreased when transgenics were under cold conditions. In addition, the transgenic plants under chilling stress displayed higher activities of superoxide dismutase (SOD) and peroxidase (POD) and less H2O2 and malondialdehyde (MDA) than the control. Moreover, the photosynthesis rate, photosystem II activity (Fv/fm), and Non-photochemical quenching (NPQ) also increased in the transgenetic plants. On the whole, overexpression of Lcε-LYC ameliorates photoinhibition and photooxidation, and decreases the sensitivity of photosynthesis to chilling stress in transgenic plants.

Overexpression of a Triticum aestivum Calreticulin gene (TaCRT1) Improves Salinity Tolerance in Tobacco.

Calreticulin (CRT) is a highly conserved and abundant multifunctional protein that is encoded by a small gene family and is often associated with abiotic/biotic stress responses in plants. However, the roles played by this protein in salt stress responses in wheat (Triticum aestivum) remain obscure. In this study, three TaCRT genes were identified in wheat and named TaCRT1, TaCRT2 and TaCRT3-1 based on their sequence characteristics and their high homology to other known CRT genes. Quantitative real-time PCR expression data revealed that these three genes exhibit different expression patterns in different tissues and are strongly induced under salt stress in wheat. The calcium-binding properties of the purified recombinant TaCRT1 protein were determined using a PIPES/Arsenazo III analysis. TaCRT1 gene overexpression in Nicotiana tabacum decreased salt stress damage in transgenic tobacco plants. Physiological measurements indicated that transgenic tobacco plants showed higher activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) than non-transgenic tobacco under normal growth conditions. Interestingly, overexpression of the entire TaCRT1 gene or of partial TaCRT1 segments resulted in significantly higher tolerance to salt stress in transgenic plants compared with their WT counterparts, thus revealing the essential role of the C-domain of TaCRT1 in countering salt stress in plants.

Overexpression of a novel cold-responsive transcript factor LcFIN1 from sheepgrass enhances tolerance to low temperature stress in transgenic plants.

As a perennial forage crop broadly distributed in eastern Eurasia, sheepgrass (Leymus chinensis (Trin.) Tzvel) is highly tolerant to low-temperature stress. Previous report indicates that sheepgrass is able to endure as low as -47.5 °C,allowing it to survive through the cold winter season. However, due to the lack of sufficient studies, the underlying mechanism towards the extraordinary low-temperature tolerance is unclear. Although the transcription profiling has provided insight into the transcriptome response to cold stress, more detailed studies are required to dissect the molecular mechanism regarding the excellent abiotic stress tolerance. In this work, we report a novel transcript factor LcFIN1 (L. chinensis freezing-induced 1) from sheepgrass. LcFIN1 showed no homology with other known genes and was rapidly and highly induced by cold stress, suggesting that LcFIN1 participates in the early response to cold stress. Consistently, ectopic expression of LcFIN1 significantly increased cold stress tolerance in the transgenic plants, as indicated by the higher survival rate, fresh weight and other stress-related indexes after a freezing treatment. Transcriptome analysis showed that numerous stress-related genes were differentially expressed in LcFIN1-overexpressing plants, suggesting that LcFIN1 may enhance plant abiotic stress tolerance by transcriptional regulation. Electrophoretic mobility shift assays and CHIP-qPCR showed that LcCBF1 can bind to the CRT/DRE cis-element located in the promoter region of LcFIN1, suggesting that LcFIN1 is directly regulated by LcCBF1. Taken together, our results suggest that LcFIN1 positively regulates plant adaptation response to cold stress and is a promising candidate gene to improve crop cold tolerance.

Chrysanthemum WRKY gene CmWRKY17 negatively regulates salt stress tolerance in transgenic chrysanthemum and Arabidopsis plants.

CmWRKY17 was induced by salinity in chrysanthemum, and it might negatively regulate salt stress in transgenic plants as a transcriptional repressor. WRKY transcription factors play roles as positive or negative regulators in response to various stresses in plants. In this study, CmWRKY17 was isolated from chrysanthemum (Chrysanthemum morifolium). The gene encodes a 227-amino acid protein and belongs to the group II WRKY family, but has an atypical WRKY domain with the sequence WKKYGEK. Our data indicated that CmWRKY17 was localized to the nucleus in onion epidermal cells. CmWRKY17 showed no transcriptional activation in yeast; furthermore, luminescence assay clearly suggested that CmWRKY17 functions as a transcriptional repressor. DNA-binding assay showed that CmWRKY17 can bind to W-box. The expression of CmWRKY17 was induced by salinity in chrysanthemum, and a higher expression level was observed in the stem and leaf compared with that in the root, disk florets, and ray florets. Overexpression of CmWRKY17 in chrysanthemum and Arabidopsis increased the sensitivity to salinity stress. The activities of superoxide dismutase and peroxidase and proline content in the leaf were significantly lower in transgenic chrysanthemum than those in the wild type under salinity stress, whereas electrical conductivity was increased in transgenic plants. Expression of the stress-related genes AtRD29, AtDREB2B, AtSOS1, AtSOS2, AtSOS3, and AtNHX1 was reduced in the CmWRKY17 transgenic Arabidopsis compared with that in the wild-type Col-0. Collectively, these data suggest that CmWRKY17 may increase the salinity sensitivity in plants as a transcriptional repressor.

Over-expression of bael quinolone synthase in tobacco improves plant vigor under favorable conditions, drought, or salt stress

Type III polyketide synthases (PKSs) catalyze the biosynthesis of various medicinally important secondary metabolites in plants, but their role in growth and stress response is unclear. Here, we overexpressed quinolone synthase (QNS) from bael in tobacco. QNS-overexpressing plants showed an overall increase in growth, photosynthetic efficiency and chlorophyll content compared to wild type plants. Second-generation (T2) transgenic plants grew to maturity, flowered early and set viable seeds under favorable conditions without yield penalty. An increased accumulation of flavonoids, phenols and alkaloids was associated with higher tolerance to drought and salinity stress in transgenic plants. Thus, bael QNS seems to function as a positive regulator of plant growth and stress response, and could be potentially used for engineering plants tolerant to abiotic stress.

Unique WSPA protein from terrestrial macroscopic cyanobacteria can confer resistance to osmotic stress in transgenic plants.

The terrestrial macroscopic cyanobacterium Nostoc commune exhibits remarkable resistance to desiccation stress. This species synthesizes abundant acidic water stress protein (WSPA) in cells upon desiccation and secretes it into the extracellular polysaccharide sheath upon rehydration. However, our knowledge about its cellular role in stress resistance is still rather limited. In this paper, we first revealed that WSPA also occurred in two other macroscopic cyanobacteria Nostoc flagelliforme and Nostoc sphaeroides, but it is more abundant in N. commune. The N. commune wspa1 gene was then heterologously expressed in Arabidopsis thaliana. Phenotypic observation found that WSPA1 conferred increased tolerance to osmotic stress in transgenic plants. The physiological indexes such as relative electrolyte leakage, malondialdehyde, proline accumulation and the maximal quantum efficiency of Photosystem II, were also improved in transgenic plants upon osmotic stress, compared to wild types. In addition, GFP fluorescence analysis of eGFP::wspa1 transgenic plant showed that WSPA1 was localized in the cytoplasm. Therefore, the role of WSPA revealed by this study mainly represented its intracellular function. In general, our research suggested that WSPA may act as a stress protein and involve cellular osmotic stress resistance.

A Gene Encoding Cold-Circadian Rhythm-RNA Binding-Like Protein (CCR-Like) from Upland Cotton (Gossypium hirsutum L.) Confers Tolerance to Abiotic Stresses in Transgenic Tobacco

Water-deficit is the major abiotic stress factor that limits the yield and quality of cotton produced around the world. We observed earlier that a CCL (CCR-like; cold-circadian rhythm-RNA binding like) gene has been differentially expressed during boll development in cotton under drought stress in the field. Isolation and functional characterization of GhCCL from upland cotton (Gossypium hirsutum L. cv. Bikaneri Narma) was carried out in the present study. We studied the GhCCL gene structure and organization and demonstrated for the first time that GhCCL may be involved in abiotic stress tolerance response in plants. RT-PCR analysis indicated that GhCCL is differentially regulated in cotton seedlings by abiotic stresses such as salt, mannitol, cold, heat, dehydration, wounding and jasmonic acid, salicylic acid, and hydrogen peroxide. In silico and subcellular localization analysis suggested that GhCCL is localized in the chloroplasts. Constitutive expression of GhCCL in tobacco (Nicotiana tabacum var. Petit Havana) conferred tolerance to water-deficit stress and salt stresses during seed germination on amended MS media. The transgenic plants showed better growth performance and increased fresh weight under long-term stress. The transgenic plants grown in the glass house tolerated water-deficit stress (by withholding water) and recovered upon rewatering (45 days) whereas WT plants did not survive. Characterization of the GhCCL promoter sequence by in silico analysis showed various light, stress, tissue specific, and hormone responsive cis-elements. The present study suggested that GhCCL positively regulates the response to abiotic stresses, especially water-deficit stress in transgenic plants and that the overexpression of GhCCL may enhance the stability of mRNA thereby conferring tolerance to abiotic stresses.

Cloning and characterisation of a pepper aquaporin, CaAQP, which reduces chilling stress in transgenic tobacco plants

Ubiquitous cell membrane proteins called aquaporins are members of major intrinsic proteins (MIPs), which control the specific transport of water molecules across cell membranes. A pepper aquaporin gene (CaAQP), which exhibits the structural features of tonoplast intrinsic proteins of the MIP subfamily, was isolated from the leaves of chilling-treated seedlings of pepper (Capsicum annuum L.) cv. P70. Assays indicated high levels of expression in young seeds, green fruits and flower buds and low levels of expression in the stems, leaves and roots of pepper. The expression patterns were strongly and rapidly induced by HgCl2, low temperature, abscisic acid, fluridone and osmotic stresses. The responsiveness of pepper seedlings pretreated with abscisic acid at low temperatures demonstrated up-regulation of CaAQP by chilling, which is potentially involved in ABA signalling. Our results indicated that overexpression of CaAQP decreased chilling stress in transgenic plants, likely by increasing the stomatal aperture under stress, increasing the rate of membrane damage during the recovery stage, thereby affecting the intercellular CO2 concentration with lower stomatal conductance and transpiration rates. VIGS of CaAQP in pepper plants caused significant growth retardation. These results suggested that CaAQP played a crucial role in the plant response to abiotic stresses.

The constitutive expression of a two transgene construct enhances the abiotic stress tolerance of chrysanthemum

Various abiotic stresses downgrade the quality and productivity of chrysanthemum. A construct carrying both CcSOS1 (from Chrysanthemum crassum) and CdICE1 (from Chrysanthemum dichrum) was constitutively expressed in the chrysanthemum variety ‘Jinba’. The transgenic plants were superior to the wild type (WT) ones with respect to their sensitivity to low temperature, drought and salinity, as measured by visible damage and plant survival. Salinity stressed transgenic plants accumulated more proline, and their level of superoxide dismutase and peroxidase activity was higher than in WT plants. At the physiological level, they suffered less loss of viable leaf area, maintained a lower leaf electrolyte conductivity and retained more chlorophyll (a+b). The ratio between the K+ and Na+ content was higher in the root, stem and median leaves of salinity stressed transgenic plants than in those of WT plants.