Rising atmospheric CO(2) levels can dilute the nitrogen (N) resource in plant tissue, which is disadvantageous to many herbivorous insects. Aphids appear to be an exception that warrants further study. The effects of elevated CO(2) (750 ppm vs. 390 ppm) were evaluated on N assimilation and transamination by two Medicago truncatula genotypes, a N-fixing-deficient mutant (dnf1) and its wild-type control (Jemalong), with and without pea aphid (Acyrthosiphon pisum) infestation. Elevated CO(2) increased population abundance and feeding efficiency of aphids fed on Jemalong, but reduced those on dnf1. Without aphid infestation, elevated CO(2) increased photosynthetic rate, chlorophyll content, nodule number, biomass, and pod number for Jemalong, but only increased pod number and chlorophyll content for dnf1. Furthermore, aphid infested Jemalong plants had enhanced activities of N assimilation-related enzymes (glutamine synthetase, Glutamate synthase) and transamination-related enzymes (glutamate oxalate transaminase, glutamine phenylpyruvate transaminase), which presumably increased amino acid concentration in leaves and phloem sap under elevated CO(2). In contrast, aphid infested dnf1 plants had decreased activities of N assimilation-related enzymes and transmination-related enzymes and amino acid concentrations under elevated CO(2). Furthermore, elevated CO(2) up-regulated expression of genes relevant to amino acid metabolism in bacteriocytes of aphids associated with Jemalong, but down-regulated those associated with dnf1. Our results suggest that pea aphids actively elicit host responses that promote amino acid metabolism in both the host plant and in its bacteriocytes to favor the population growth of the aphid under elevated CO(2).

Elevated CO2 compromises the resistance of leguminous plants against chewing insects, but little is known about whether elevated CO2 modifies the resistance against phloem-sucking insects or whether it has contrasting effects on the resistance of legumes that differ in biological nitrogen fixation. We tested the hypothesis that the physical and chemical resistance against aphids would be increased in Jemalong (a wild type of Medicago truncatula) but would be decreased in dnf1 (a mutant without biological nitrogen fixation) by elevated CO2. The non-glandular and glandular trichome density of Jemalong plants increased under elevated CO2, resulting in prolonged aphid probing. In contrast, dnf1 plants tended to decrease foliar trichome density under elevated CO2, resulting in less surface and epidermal resistance to aphids. Elevated CO2 enhanced the ineffective salicylic acid-dependent defence pathway but decreased the effective jasmonic acid/ethylene-dependent defence pathway in aphid-infested Jemalong plants. Therefore, aphid probing time decreased and the duration of phloem sap ingestion increased on Jemalong under elevated CO2, which, in turn, increased aphid growth rate. Overall, our results suggest that elevated CO2 decreases the chemical resistance of wild-type M. truncatula against aphids, and that the host's biological nitrogen fixation ability is central to this effect.

Background: Probiotics have been associated with the treatment of depression and anxiety. However, the results reported in the literature have been inconsistent, and no meta-analysis specifically reported probiotics used on participants with varying levels of emotional state. Methods: This meta-analysis aimed to study the effectiveness of probiotics on anxious or depressive symptomatology for participants under stress conditions or with a depressive or anxiety disorder diagnosis. Medline, PubMed, EMBASE, and the Cochrane Library were searched through December 2019 for randomized controlled trials (RCTs). The primary outcomes were depression and anxiety scores. Main inclusion criteria: RCTs of probiotics for participants with a mood or emotional disorder diagnosis or under stress situations; and all participants were adults (age ≥16 years); Assessed by the modified Jadad assessment scale found seven high-quality studies and three low-quality studies. Results: Ten clinical trials (n = 685 total participants) were included based on the inclusion and exclusion criteria. All studies were assessed as low or moderate risk of bias. The meta-analysis showed that probiotics could significantly reduce the depression scale for patients with anxiety and depression, and healthy participants under stress. However, there was no significant difference between the probiotics and placebo groups in the reduction of patient anxiety scores, even if they are depressive or anxious patients or healthy participants under stress. Subgroup analysis revealed that probiotics had significant effect on depressive symptoms just in patients with depression, and no significant change in anxiety in patients, and no improvement in participant performance under stress. Conclusions: Probiotics could alleviate depressive symptoms in patients with a depression diagnosis or depression scores also in anxiety disorder diagnosis, and suggesting that probiotics may be adjunct therapies for mood or emotional disorders. Chao et al. Probiotics on Depression or Anxiety Therefore, it is essential that probiotics could be more involved in the treatment of patients with depression in the future. The evidence of probiotics successfully treating depression is still insufficient, and more high-quality studies on patients with depression are still needed.