Dataset Information

UV-B Physiological Changes Under Conditions of Distress and Eustress in Sweet Basil.

ABSTRACT: UV-B radiation has been previously reported to induce protective or deleterious effects on plants depending on the UV-B irradiation doses. To elucidate how these contrasting events are physiologically coordinated, we exposed sweet basil plants to two UV-B doses: low (8.5 kJ m-2 day-1, 30 min exposure) and high (68 kJ m-2 day-1, 4 h exposure), with the plants given both doses once continuously in a single day. Physiological tests during and after both UV-B exposures were performed by comparing the stress-induced damage and adverse effects on photosynthetic activity, the concentration and composition of photosynthetic and non-photosynthetic pigments, and stress-related hormones biosynthesis in basil plants. Our results showed that upon receiving a high UV-B dose, a severe inactivation of oxygen evolving complex (OEC) activity at the PSII donor side and irreversible PSII photodamage caused primarily by limitation of the acceptor side occurred, which overloaded protective mechanisms and finally led to the death of the plants. In contrast, low UV-B levels did not induce any signs of UV-B stress injuries. The OEC partial limitation and the inactivation of the electron transport chain allowed the activation of photoprotective mechanisms, avoiding irreversible damage to PSII. Overall results indicate the importance of a specific response mechanisms regulating photoprotection vs irreversible photoinhibition in basil that were modulated depending on the UV-B doses.

SUBMITTER: Mosadegh H

PROVIDER: S-EPMC6843199 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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UV-B Physiological Changes Under Conditions of Distress and Eustress in Sweet Basil.

Mosadegh Haana H Trivellini Alice A Lucchesini Mariella M Ferrante Antonio A Maggini Rita R Vernieri Paolo P Sodi Anna Mensuali AM

Plants (Basel, Switzerland) 20191004 10

UV-B radiation has been previously reported to induce protective or deleterious effects on plants depending on the UV-B irradiation doses. To elucidate how these contrasting events are physiologically coordinated, we exposed sweet basil plants to two UV-B doses: low (8.5 kJ m-2 day-1, 30 min exposure) and high (68 kJ m-2 day-1, 4 h exposure), with the plants given both doses once continuously in a single day. Physiological tests during and after both U ...[more]

PMID: 31590329

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Project description:UV-A radiation (320-400 nm) is an abiotic stressor that may be used to enhance the production of beneficial secondary metabolites in crops such as leafy vegetables. However, tradeoffs between enhanced phytochemical contents and overall growth/yield reductions have been reported. The responses varied depending on the UV-A intensity, spectral peak, exposure time, species, and varieties. We quantified the changes in growth, morphology, photosynthesis, and phenolic contents of sweet basil grown under a base red/blue/green LED light with four supplemental UV-A intensity treatments (0, 10, 20, and 30 W·m-2) in an indoor environment over 14 days. The objective was to determine whether UV-A radiation could be utilized to improve both yield and quality of high-value sweet basil in a controlled production environment. Biomass harvested at 14 days after treatment (DAT) was highest under mild-intensity UV-A treatment of 10 W·m-2 and lowest under high-intensity UV-A treatment of 30 W·m-2. The total leaf area and the number of leaves were significantly lower under the 30 W·m-2 treatment than under the 10 and 20 W·m-2 treatments at 14 DAT. The maximum quantum efficiency of photosystem II (PSII) for photochemistry (Fv/Fm ) showed a gradual decrease under the 20 and 30 W·m-2 treatments from 3 to 14 DAT, whereas Fv/Fm remained relatively constant under the 0 and 10 W·m-2 treatments over the entire 14 days. The leaf net photosynthesis rate showed a significant decrease of 17.4% in the 30 W·m-2 treatment compared to that in the 10 W·m-2 treatment at 14 DAT. Phenolic contents (PAL enzyme activity, total phenolic concentration, and antioxidant capacity) were the highest under the 20 W·m-2 treatment, followed by the 10, 30, and 0 W·m-2 treatments. Overall, our results indicate that the biomass production and accumulation of beneficial phenolic compounds in sweet basil varied depending on the intensity and duration of UV-A application. Mild UV-A radiation (10-20 W·m-2) can be a beneficial stressor to improve sweet basil yield and quality over relatively long-term cultivation.

Project description:Sweet basil (Ocimum basilicum) is an economically important herb and its global production is threatened by basil downy mildew caused by the obligate biotrophic oomycete Peronospora belbahrii. Effective tools are required for functional understanding of its genes involved in synthesis of valuable secondary metabolites in essential oil and disease resistance, and breeding for varieties with improved traits. Clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 gene editing technology has revolutionized crop breeding and functional genomics. The applicability and efficacy of this genomic tool in the allotetraploid sweet basil were tested by editing a potential susceptibility (S) gene ObDMR1, the basil homolog of Arabidopsis DMR1 (Downy Mildew Resistant 1) whose mutations conferred nearly complete resistance against Arabidopsis downy mildew pathogen, Hyaloperonospora arabidopsidis. Two single guide RNAs targeting two different sites of the ObDMR1 coding sequence were designed. A total of 56 transgenic lines were obtained via Agrobacterium-mediated stable transformation. Mutational analysis of 54 T0 transgenic lines identified 92.6% lines carrying mutations at target 1 site, while a very low mutation frequency was detected at target 2 site. Deep sequencing of six T0 lines revealed various mutations at target 1 site, with a complete knockout of all alleles in one line. ObDMR1 homozygous mutant plants with some being transgene free were identified from T1 segregating populations. T2 homozygous mutant plants with 1-bp frameshift mutations exhibited a dwarf phenotype at young seedling stage. In summary, this study established a highly efficient CRISPR/Cas9-mediated gene editing system for targeted mutagenesis in sweet basil. This system has the capacity to generate complete knockout mutants in this allotetraploid species at the first generation of transgenic plants and transgene-free homozygous mutants in the second generation. The establishment of this system is expected to accelerate basil functional genomics and breeding.

Dataset Information

UV-B Physiological Changes Under Conditions of Distress and Eustress in Sweet Basil.

Publications

UV-B Physiological Changes Under Conditions of Distress and Eustress in Sweet Basil.

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