Multitraits evaluation of a Solanum pennellii introgression tomato line challenged by combined abiotic stress

Effects of combined extreme cold and drought stress on growth, photosynthesis, and physiological characteristics of cool-season grasses

Abiotic stress is an important factor affecting turf establishment and limiting the sustainability of the turf industry. To alleviate the effects of combined cold and drought stress in cold- and drought-prone regions, it is essential to select and introduce turfgrass germplasms that are suitable for these conditions for successful turf establishment. Thus, we evaluated the effects of combined extreme cold and drought stress on the morphological, plant leaf functional, photosynthetic, and physiological and biochemical traits of 16 wild annual bluegrass (Poa annua) germplasms. We found that there were significant differences (P < 0.05) among different provenances, combined cold and drought stress, and the main interaction factors. Combined cold and drought stress altered the morphological characteristics of the 16 germplasms to varying degrees. Furthermore, combined cold and drought stress significantly reduced the net photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), instantaneous water use efficiency (WUE), chlorophyll content, chlorophyll fluorescence parameters, accumulated intercellular CO2 concentration (Ci), and relative electrical conductivity (REC) and malondialdehyde (MDA), proline (Pro), soluble protein (SP), soluble sugar (SS), superoxide anion (O2.-), hydrogen peroxide (H2O2), and hydroxyl radical (·OH) and other active oxygen, and increased the superoxide dismutase activity (SOD), peroxidase activity (POD), catalase activity (CAT), ascorbate peroxidase activity (APX) and glutathione reductase (GR) activities. Comprehensive evaluation using principal component analysis (PCA), membership function analysis, and clustered heatmaps indicated that the 'HZ' germplasm had stronger combined cold and drought tolerance, whereas the 'ZQ' germplasm was more sensitive to combined cold and drought, which was roughly consistent with the order of morphological damage symptoms. Therefore, it is recommended to use the 'HZ' germplasm for planting projects in cold- and drought-prone areas, while the 'ZQ' germplasm is more suitable for use under warmer and non-water-deficient conditions.

Intra- and inter-specific reproductive barriers in the tomato clade

Tomato (Solanum lycopersicum L.) domestication and later introduction into Europe resulted in a genetic bottleneck that reduced genetic variation. Crosses with other wild tomato species from the Lycopersicon clade can be used to increase genetic diversity and improve important agronomic traits such as stress tolerance. However, many species in the Lycopersicon clade have intraspecific and interspecific incompatibility, such as gametophytic self-incompatibility and unilateral incompatibility. In this review, we provide an overview of the known incompatibility barriers in Lycopersicon. We begin by addressing the general mechanisms self-incompatibility, as well as more specific mechanisms in the Rosaceae, Papaveraceae, and Solanaceae. Incompatibility in the Lycopersicon clade is discussed, including loss of self-incompatibility, species exhibiting only self-incompatibility and species presenting both self-compatibility and self-incompatibility. We summarize unilateral incompatibility in general and specifically in Lycopersicon, with details on the 'self-compatible x self-incompatible' rule, implications of self-incompatibility in unilateral incompatibility and self-incompatibility-independent pathways of unilateral incompatibility. Finally, we discuss advances in the understanding of compatibility barriers and their implications for tomato breeding.

BLZ8 activates a plastidial peroxiredoxin and a ferredoxin to protect Chlamydomonas reinhardtii against oxidative stress

Reactive oxygen species (ROS) cause damage to various cellular processes in almost all organisms, in particular photosynthetic organisms that depend on the electron transfer chain for CO2 fixation. However, the detoxifying process to mitigate ROS damage has not been studied intensively in microalgae. Here, we characterized the ROS detoxifying role of a bZIP transcription factor, BLZ8, in Chlamydomonas reinhardtii. To identify downstream targets of BLZ8, we carried out comparative genome-wide transcriptomic profiling of BLZ8 OX and its parental CC-4533 under oxidative stress conditions. Luciferase reporter activity assays and RT-qPCR were performed to test whether BLZ8 regulates downstream genes. We performed an in silico functional gene network analysis and an in vivo immunoprecipitation assay to identify the interaction between downstream targets of BLZ8. Comparative transcriptomic analysis and RT-qPCR revealed that overexpression of BLZ8 increased the expression levels of plastid peroxiredoxin1 (PRX1) and ferredoxin-5 (FDX5) under oxidative stress conditions. BLZ8 alone could activate the transcriptional activity of FDX5 and required bZIP2 to activate transcriptional activity of PRX1. Functional gene network analysis using FDX5 and PRX1 orthologs in A. thaliana suggested that these two genes were functionally associated. Indeed, our immunoprecipitation assay revealed the physical interaction between PRX1 and FDX5. Furthermore, the complemented strain, fdx5 (FDX5), recovered growth retardation of the fdx5 mutant under oxidative stress conditions, indicating that FDX5 contributes to oxidative stress tolerance. These results suggest that BLZ8 activates PRX1 and FDX5 expression, resulting in the detoxification of ROS to confer oxidative stress tolerance in microalgae.

Bacteriophage-mediated biosynthesis of MnO2NPs and MgONPs and their role in the protection of plants from bacterial pathogens

Introduction

Xanthomonas oryzae pv. oryzae (Xoo) is the plant pathogen of Bacterial Leaf Blight (BLB), which causes yield loss in rice.

Methods

In this study, the lysate of Xoo bacteriophage X3 was used to mediate the bio-synthesis of MgO and MnO₂. The physiochemical features of MgONPs and MnO₂NPs were observed via Ultraviolet - Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Transmission/Scanning electron microscopy (TEM/SEM), Energy dispersive spectrum (EDS), and Fourier-transform infrared spectrum (FTIR). The impact of nanoparticles on plant growth and bacterial leaf blight disease were evaluated. Chlorophyll fluorescence was used to determine whether the nanoparticles application were toxic to the plants.

Results

An absorption peak of 215 and 230 nm for MgO and MnO₂, respectively, confirmed nanoparticle formation via UV-Vis. The crystalline nature of the nanoparticles was detected by the analysis of XRD. Bacteriological tests indicated that MgONPs and MnO₂NPs sized 12.5 and 9.8 nm, respectively, had strong in vitro antibacterial effects on rice bacterial blight pathogen, Xoo. MnO₂NPs were found to have the most significant antagonist effect on nutrient agar plates, while MgONPs had the most significant impact on bacterial growth in nutrient broth and on cellular efflux. Furthermore, no toxicity to plants was observed for MgONPs and MnO₂NPs, indeed, MgONPs at 200 μg/mL significantly increased the quantum efficiency of PSII photochemistry on the model plant, Arabidopsis, in light (ΦPSII) compared to other interactions. Additionally, significant suppression of BLB was noted in rice seedlings amended with the synthesized MgONPs and MnO₂NPs. MnO₂NPs showed promotion of plant growth in the presence of Xoo compared to MgONPs.

Conclusion

An effective alternative for the biological production of MgONPs and MnO₂NPs was reported, which serves as an effective substitute to control plant bacterial disease with no phytotoxic effect.