Nano-silver modifies the vase life of cut herbaceous peony (<Emphasis Type="Italic">Paeonia lactiflora</Emphasis> Pall.) flowers

Herbaceous peony (Paeonia lactiflora Pall.) is a popular high-grade cut flower because of higher ornamental value. However, its short flowering time severely restricts the production and application of cut P. lactiflora flowers. In this study, nano-silver (NS) was applied to prolong the vase life of cut P. lactiflora flowers. Under the NS treatment, related physiological indices including relative electrical conductivity (REC), malondialdehyde (MDA), superoxide anion free radical (O₂^·?), hydrogen peroxide (H₂O₂) and free proline contents, and protective enzyme activities including superoxide dismutase (SOD), peroxidase (POD) and ascorbic acid peroxidase (APX) all increased in cut P. lactiflora flowers except soluble protein. Meanwhile, NS treatment increased relative water uptake (RWU) and Ag⁺ distribution. Moreover, the observation of microstructures indicated that the stem-ends without NS treatment were blocked by microbes which were identified as Alternaria sp. and Phoma sp., and NS effectively inhibited their growth by antibacterial efficacy observation. Additionally, three aquaporin genes (AQPs) including two plasma membrane intrinsic protein genes (PlPIP1;2, PlPIP2;1) and one NOD26-like intrinsic protein gene (PlNIP) were isolated, PlPIP1;2, and PlPIP2;1 that were induced by NS treatment took common effects on maintaining the water balance of cut P. lactiflora flowers. Consequently, the vase life of cut P. lactiflora flowers was prolonged and flower fresh weight together with flower diameter was well kept because of these above factors. These results would provide a theoretical basis for prolonging the vase life and improving the ornamental quality of cut P. lactiflora flowers with NS application.     

The Stress of Suicide: Temporal and Spatial Expression of Putative Heat Shock Protein 70 Protect the Cells from Heat Injury in Wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis>)

Heat stress adversely affects growth, development, and yield of winter wheat (Triticum aestivum). Plants have, however, evolved mechanisms to adapt to such conditions mainly by the expression of stress-associated chaperones, the heat shock proteins (HSPs), for modulating the tolerance level. Here, we report cloning of cytosolic putative HSP70 of 1678 bp from a thermotolerant cultivar (C306) of wheat (T. aestivum). A BLASTn search showed maximum homology with the predicted HSP70 protein reported from Hordeum vulgare (accession no AK354795.1). In silico characterization showed the presence of a nucleotide-binding domain of the sugar kinase/HSP70/actin superfamily in the sequence. Putative HSP70 showed temporal and spatial variations in the expression under heat stress (HS). We observed the abundance of HSP70 protein, H₂O₂, proline, and guaiacol peroxidase activity during the seed-hardening stage under HS; accumulation was, however, higher in the thermotolerant C306 than in thermosusceptible HD2329 cultivar. A gradual decrease in cell membrane stability (CMS) and an increase in total antioxidant capacity (TAC) were observed in both the cultivars at the different stages of growth. The expression of HSP70 showed a negative correlation with CMS and a positive correlation with TAC under HS; changes were less pronounced in C306 than in HD2329 at all the stages of growth studied. HSP70 seems to play diverse roles associated with thermotolerance, and partially protect wheat from terminal HS. Being the important member of family of the HSPs, HSP70 needs to be studied in detail, to be used for developing climate-smart wheat crops, through genetic engineering/breeding approaches.     

Calcium chloride improves photosynthesis and water status in the C<Subscript>4</Subscript> succulent xerophyte <Emphasis Type="Italic">Haloxylon ammodendron</Emphasis> under water deficit

It is important to reveal the mechanism of plants coping with heat stress, which results in a severe retardation in crop growth and development. Although Synaptotagmin A (SYTA) regulates the cell endocytosis and the plasma membrane reparation of Arabidopsis, its roles in heat resistance are not well understood. In this study, we obtained the new finding that SYTA is related to the heat resistance of Arabidopsis. In the SYTA overexpression strains, the germination rate of the seeds and the survival rate of the seedlings improved after heat shock treatment, and their degree of membrane peroxidation was reduced. However, syta mutant showed the opposite results. Meanwhile, the expressions of some heat stress signal pathway genes were higher in SYTA overexpression strains than that in wild-type strains, and were lower in syta mutant strains. These results suggested that SYTA responded positively to heat shock and was involved in the heat stress signal pathway.     

Overexpression of <Emphasis Type="Italic">MuHSP70</Emphasis> gene from <Emphasis Type="Italic">Macrotyloma uniflorum</Emphasis> confers multiple abiotic stress tolerance in transgenic <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

A 70-KD heat shock protein (HSP70) is one of the most conserved chaperones. It is involved in de novo protein folding and prevents the aggregation of unfolded proteins under lethal environmental factors. The purpose of this study is to characterise a MuHSP70 from horsegram (Macrotyloma uniflorum) and elucidating its role in stress tolerance of plants. A MuHSP70 was cloned and characterised from a natural drought stress tolerant HPK4 variety of horsegram (M. uniflorum). For functional characterization, MuHSP70 was overexpressed in transgenic Arabidopsis. Overexpression of MuHSP70 was found to provide tolerance to the transgenic Arabidopsis against various stresses such as heat, cold, drought, salinity and oxidative stress. MuHSP70 transgenics were observed to maintain the shoot biomass, root length, relative water content, and chlorophyll content during exposure to multi-stresses relative to non-transgenic control. Transgenic lines have further shown the reduced levels of MDA, H₂O₂, and proteolytic activity. Together, these findings suggest that overexpression of MuHSP70 plays an important role in improving abiotic stress tolerance and could be a crucial candidate gene for exploration in crop improvement program.