Enhanced In Vitro Plant Morphogenesis of Tobacco: Unveiling Indoleamine-Modulated Adaptogenic Properties of Tulsi (Ocimum sanctum L.).

The medicinal plant tulsi (Ocimum sanctum L.) is acknowledged for its invigorating and healing properties that enhance resilience to stress in various human and animal models by modulating antioxidant compounds. While extensive research has documented these effects in humans, the adaptogenic potential of tulsi in stressful in vitro plant systems has not been explored. This study aimed to elucidate the adaptogenic properties of tulsi leaf extract on the in vitro regeneration of tobacco leaf explants through an investigation of the indoleamines at different developmental stages. Shoot regeneration from leaf explants on the medium supplemented with tulsi extract (20%) was compared to the control, and the differences in indoleamine compounds were analyzed using ultra-performance liquid chromatography. Treatment of the explants with the extract resulted in an almost two-fold increase in the number of regenerants after four weeks of culture, and 9% of the regenerants resembled somatic embryo-like structures. The occurrence of browning in the extract-treated explants stopped on day 10, shoots began to develop, and a significant concentration of tryptamine and N-acetyl-serotonin accumulated. A comparative analysis of indoleamine compounds in intact and cut tobacco leaves also revealed the pivotal role of melatonin and 2-hydroxymelatonin functioning as antioxidants during stress adaptation. This study demonstrates that tulsi is a potent adaptogen that is capable of modulating plant morphogenesis in vitro, paving the way for further investigations into the role of adaptogens in plant stress biology.

Salicylic and Jasmonic Acid Synergism during Black Knot Disease Progression in Plums.

Black knot (BK) is a deadly disease of European (Prunus domestica) and Japanese (Prunus salicina) plums caused by the hemibiotrophic fungus Apiosporina morbosa. Generally, phytopathogens hamper the balance of primary defense phytohormones, such as salicylic acid (SA)-jasmonic acid (JA) balance, for disease progression. Thus, we quantified the important phytohormone titers in tissues of susceptible and resistant genotypes belonging to European and Japanese plums at five different time points. Our previous results suggested that auxin-cytokinins interplay driven by A. morbosa appeared to be vital in disease progression by hampering the plant defense system. Here, we further show that such hampering of disease progression is likely mediated by perturbance in SA, JA, and, to some extent, gibberellic acid. The results further indicate that SA and JA in plant defense are not always necessarily antagonistic as most of the studies suggest but can be different, especially in woody perennials. Together, our results suggest that the changes in phytohormone levels, especially in terms of SA and JA content due to BK infection and progression in plums, could be used as phytohormonal markers in the identification of BK-resistant cultivars.

Hormonal Interplay Leading to Black Knot Disease Establishment and Progression in Plums.

Black Knot (BK) is a deadly disease of European (Prunus domestics) and Japanese (Prunus salicina) plums caused by the hemibiotrophic fungus Apiosporina morbosa. After infection, the appearance of warty black knots indicates a phytohormonal imbalance in infected tissues. Based on this hypothesis, we quantified phytohormones such as indole-3-acetic acid, tryptophan, indoleamines (N-acetylserotonin, serotonin, and melatonin), and cytokinins (zeatin, 6-benzyladenine, and 2-isopentenyladenine) in temporally collected tissues of susceptible and resistant genotypes belonging to European and Japanese plums during of BK progression. The results suggested auxin-cytokinins interplay driven by A. morbosa appears to be vital in disease progression by hampering the plant defense system. Taken together, our results indicate the possibility of using the phytohormone profile as a biomarker for BK resistance in plums.

Straw Mulch Induced Indoleamines Alleviate Reproductive Depression in Cold Sensitive Hazelnut Cultivars.

Climate change is forcing physiological changes, especially in temperate trees, in which the reproduction phase has been affected harshly, eventually resulting in poor performance. Erratic fluctuations during the flowering periods, predominantly in cold-sensitive, yet industry-desired (sourced), hazelnut cultivars have been causing at least a 10-fold decline in the nut yield. Indoleamines have been noted to provide protection during such abiotic stress conditions. In this study, we investigated the potential involvement of the indoleamine pathway in countering reproductive depression in cold-sensitive hazelnuts by blanketing the ground with wheat straw mulch. The female flower ratio; titers of tryptophan, serotonin, and melatonin; and indoleamine pathway gene regulation were the endpoints for assessing the effects of straw mulch. In the preceding year, we noted that the occurrence of phenological events through the modulation of indoleamines was necessitated via percolation of snowmelt into the rootzone. Otherwise, reproductive depression was noted, especially in harsh conditions, such as 'no snow' or when the rootzone was covered with a plastic sheet to disallow water percolation. When cold-sensitive hazelnut cultivars that were subjected to such deleterious treatments in the preceding years' experiments were treated with straw mulch, the female flower ratio was unaffected and remained on par with that of the cold-hardy locally adapted cultivars. Tryptophan accumulation improved in the (cold-sensitive) sourced cultivars treated with straw mulch and was available as serotonin to counter the cold stress. Lower titers of melatonin explained the slight improvement in female ratio in the sourced cultivars blanketed with straw mulch. ASMT gene regulation via straw mulch treatment emphasized its role in abiotic stress mitigation. A negative trend was noted when improved flowering was compared to the decreased expression of the ASMT gene. Horticultural changes, such as mulch, should provide mitigating solutions to relieve reproductive depression in cold-sensitive hazelnuts, alongside implications in other horticultural crops. The indoleamine toolkit (cellular markers) developed in this study provides insights into the mechanisms of cold sensitivity (abiotic stress) and plausible solutions, such as exogenous application of indoleamines, to propagate climate resilient plant materials with an enhanced capacity to mitigate abiotic stress conditions.

Indoleamines Impart Abiotic Stress Tolerance and Improve Reproductive Traits in Hazelnuts.

Hazelnuts have recently gathered tremendous attention due to the expansion of the confectionary industry. However, the sourced cultivars fail to perform in initial phase of cultivation as they enter bare survival mode due to changes in climatic zones, for example, Southern Ontario, where the climate is continental, as opposed to the milder climate in Europe and Turkey. Indoleamines have been shown to counter abiotic stress and modulate vegetative and reproductive development of plants. Here, we examined the effect of indoleamines on the flowering response of the dormant stem cuttings of sourced hazelnut cultivars in controlled environment chambers. The stem cuttings were exposed to sudden summer-like conditions (abiotic stress) and the female flower development was assessed in relation to endogenous indoleamine titers. The sourced cultivars responded well to serotonin treatment by producing more flowers compared to the controls or other treatments. The probability of buds resulting in female flowers was highest in the middle region of the stem cuttings. It is interesting to note that the tryptamine titers of the locally adapted, and N-acetyl serotonin titers of native hazelnut cultivars, provided the best explanation for adaptation to the stress environment. Titers of both compounds were compromised in the sourced cultivars which resorted mostly to serotonin concentrations to counter the stress. The indoleamines tool kit identified in this study could be deployed in assessing cultivars for stress adaptation attributes.

Preharvest Spray Hexanal Formulation Enhances Postharvest Quality in 'Honeycrisp' Apples by Regulating Phospholipase D and Calcium Sensor Proteins Genes.

'Honeycrisp' (Malus domestica Borkh.), a premium applecultivar, is highly susceptible to bitter pit and decline in quality during long-term storage. In order to enhance the quality, an aqueous composition containing hexanal was applied as a preharvest spray. The effects of hexanal were assessed on the treated fruit and compared with HarvistaTM (a sprayable 1-Methylcyclopropene based commercial formulation) applied and control fruit under both cold (2.5 °C; four months) and cold after room temperature storage (20 °C; 14 days) conditions. Color, firmness, and total soluble solids (TSS) did not show a significant change in response to any treatment at harvest, while abscisic acid (ABA) significantly reduced and tryptophan increased in response to hexanal, compared to HarvistaTM and control. The treatment effects on quality traits were observed during storage. Both hexanal and HarvistaTM sprayed apples had higher TSS under both cold and room temperature storage. In addition, both sprays enhanced firmness at room temperature storage. However, the effects of sprays on other quality traits showed a different pattern. Apples sprayed with hexanal had lower phospholipase D enzyme (PLD) activity, lower incidence of bitter pit, and decreased expression of MdPLDα1 compared to HarvistaTM and control. On the other hand, HarvistaTM treated fruit produced lower ethylene. Both sprays decreased the expression of MdPLDα4, MdCaM2, MdCaM4 and MdCML18 genes. Generally, PLD alpha has a direct role in promoting fruit senescence, whereas the calcium senor proteins (CaM/CMLs) may involve in fruit ripening process via calcium and ethylene interactions. Therefore, improved postharvest qualities, including the lower incidence of bitter pit in hexanal treated 'Honeycrisp', may be associated with lower membrane damage due to lower PLD enzyme activity and decreased expression of MdPLDα1 and MdPLDα4 genes throughout the storage period.

Laboratory studies of insecticide efficacy and resistance in Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) populations from British Columbia, Canada.

BACKGROUND: Spotted wing drosophila (SWD), Drosophila suzukii (Matsumura), control can be improved with better knowledge of insecticide efficacy, timing of sprays and rotations with registered products during the crop year. An efficacy bioassay was applied to study the dose response of adult laboratory-reared SWD collected from a cherry orchard in British Columbia (BC), Canada, to 11 insecticides. RESULTS: Age- and sex-specific toxicities with the most effective insecticide, malathion, determined that older male SWD were significantly more susceptible than females. The selection for polygenic resistance to malathion using repeated exposure to sublethal concentrations with both the original and an additional blueberry-collected population of laboratory-reared SWD determined no significant difference in susceptibility after 30 generations. CONCLUSION: Possible reasons reported in D. melanogaster studies where resistance did not occur after insecticide selection included avoidance and associated microbial complexes. The low level of malathion resistance observed in the selected SWD populations and a field-collected population is useful information in the development of insecticide resistance management programmes. © 2016 Her Majesty the Queen in Right of Canada Pest Management Science © 2016 Society of Chemical Industry.

Effect of low doses of precocene on reproduction and gene expression in green peach aphid.

Insect reproduction can be stimulated by exposure to sublethal doses of insecticide that kill the same insects at high doses. This bi-phasic dose response to a stressor is known as hormesis and has been demonstrated with many different insect-insecticide models. The specific mechanisms of the increased reproduction in insects following sublethal pesticide exposure are unknown, but may be related to juvenile hormone (JH), which has a major role in regulation of metamorphosis and reproductive development in insects. We tested the hypothesis that exposure to sublethal concentrations of precocene, an antagonist of JH, would not result in stimulated reproductive outputs in the green peach aphid, Myzus persicae, as can be demonstrated with many neurotoxic insecticides. We also measured JH titers and the expression of various developmental (FPPS I), stress response (Hsp60), and dispersal (OSD, TOL and ANT) genes in aphids following exposure to the same precocene treatments. We found that when aphid nymphs were treated with certain sublethal concentrations of precocene, 1.5- to 2-fold increased reproductive stimulation occurred when they became adults, but this effect subsided in the following generation. Precocene treatments to nymphs resulted in no measurable effects on JH levels in subsequent reproducing adults. Although we detected major effects on gene expression following some precocene treatments (e.g. 100- to 300-fold increased expression of some genes), there were no clear relationships between gene expression and reproductive responses for a given treatment.

Gene expression during imidacloprid-induced hormesis in green peach aphid.

Imidacloprid-induced hormesis in the form of stimulated reproduction has previously been reported in green peach aphid, Myzus persicae. Changes in gene expression accompanying this hormetic response have not been previously investigated. In this study, expression of stress response (Hsp60), dispersal (OSD, TOL and ANT), and developmental (FPPS I) genes were examined for two generations during imidacloprid-induced reproductive stimulation in M. persicae. Global DNA methylation was also measured to test the hypothesis that changes in gene expression are heritable. At hormetic concentrations, down-regulation of Hsp60 was followed by up-regulation of this gene in the subsequent generation. Likewise, expression of dispersal-related genes and FPPS I varied with concentration, life stage, and generation. These results indicate that reproductive hormesis in M. persicae is accompanied by a complex transgenerational pattern of up- and down-regulation of genes that likely reflects trade-offs in gene expression and related physiological processes during the phenotypic dose-response. Moreover, DNA methylation in second generation M. persicae occurred at higher doses than in first-generation aphids, suggesting that heritable adaptability to low doses of the stressor might have occurred.

Transgenerational shifts in reproduction hormesis in green peach aphid exposed to low concentrations of imidacloprid.

Hormesis is a biphasic phenomenon that in toxicology is characterized by low-dose stimulation and high-dose inhibition. It has been observed in a wide range of organisms in response to many chemical stressors, including insects exposed to pesticides, with potential repercussions for agriculture and pest management. To address questions related to the nature of the dose-response and potential consequences on biological fitness, we examined transgenerational hormesis in the green peach aphid, Myzus persicae, when exposed to sublethal concentrations of the insecticide imidacloprid. A hormetic response in the form of increased reproduction was consistently observed and a model previously developed to test for hormesis adequately fit some of our data. However, the nature of the dose-response differed within and across generations depending upon the duration and mode of exposure. Decreased reproduction in intermediate generations confirmed that fitness tradeoffs were a consequence of the hormetic response. However, recovery to levels of reproduction equal to that of controls in subsequent generations and significantly greater total reproduction after four generations suggested that biological fitness was increased by exposure to low concentrations of the insecticide, even when insects were continuously exposed to the stressor. This was especially evident in a greenhouse experiment where the instantaneous rate of population increase almost doubled and total aphid production more than quadrupled when aphids were exposed to potato plants systemically treated with low amounts of imidacloprid. Our results show that although fitness tradeoffs do occur with hormetic responses, this does not necessarily compromise overall biological fitness.