Changes in light quality alter physiological responses of soybean to thiamethoxam.

MAIN CONCLUSION: The interaction between neighboring weed-induced far-red enriched light and thiamethoxam can significantly alter soybean seedling morphology, nodulation, isoflavone levels, UV-absorbing phenolics, and carbon and nitrogen content. Neonicotinoid insecticides that are widely used on major crop plants can enhance plant growth and yield. Although the underlying mechanism of this enhanced growth and yield is not clear, recent studies suggest that neonicotinoids such as thiamethoxam (TMX) may exert their effects at least in part via signals that involve salicylic acid (SA) and jasmonic acid (JA). In the current research, effects of TMX on morphological and physiological responses of soybean have been compared under far-red-depleted (FR-D) and far-red-enriched (FR-E) light reflected by neighboring weeds. TMX significantly enhanced shoot and root growth but did not prevent stem elongation under FR-E light. Also, TMX did not prevent reductions in shoot carbon content and shoot carbon to nitrogen ratio under FR-E light. Despite similarities between these TMX effects in soybean and those known for SA and JA in other plant species, TMX significantly enhanced root-nodule numbers per plant and levels of root isoflavones malonyl-daidzin and malonyl-genistin under FR-E light only. These results suggest that the combined effect of FR-E light and TMX triggers a mechanism that operates concomitantly to enhance root isoflavones and nodulation in soybean.

Vineyard light manipulation and silicon enhance ethylene-induced anthocyanin accumulation in red table grapes.

Red color resulted from anthocyanin pigment, is an essential trait for premium table grape production. Anthocyanin biosynthesis occurs through the flavonoid pathway which includes several enzymatic reactions coded by different genes. The expression of these genes is regulated by different cultural practices, cultivars, environmental conditions, and plant hormones. Recently, we reported that the anthocyanin pathway is regulated by several factors such as light and antioxidant activity. Despite the advances in cultural practices, it is still challenging to produce table grapes with high coloration, especially under the current and expected global climate change in warmer areas such as California. In the current study, we deployed two approaches to improve the accumulation of red pigment in table grapes. The first approach involves improving the expression of critical genes involved in the anthocyanin pathway through hormonal treatments and light manipulation using a reflective ground cover (RGC). The second approach was to reduce the negative effect of heat stress through stimulation of the antioxidant pathway to help remove free radicals. Treatments included ethephon (ET) at 600 mg/L, silicon (Si) at 175 mg/L, and a commercial light-reflective white ground cover (RGC) alone and in various combinations. Treatments were conducted either with or without a combination of cluster-zone leaf removal at veraison (LR) on Flame seedless (Vitis vinifera L.). Data collected in 2019 and 2020 showed that the best treatment to improve berry coloration was using ET in combination with Si and RGC, applied at veraison. Adding the LR to this combination did not improve berry color any further, but rather caused a reduction in color development. RGC without conducting LR at veraison significantly increased the quantity of reflected blue and red lights as well as the red (R) to far-red (FR) ratio (R: FR) around clusters. Results were in accordance with the increase in gene expression of flavonoid-3-O-glucosyltransferase (UFGT), a key gene in the anthocyanin biosynthesis pathway, as well as Peroxidase dismutase (POD). Manipulating the light spectrum and application of silicon in combination with the ethephon treatment could be used in table grape vineyards to improve the ethylene-induced anthocyanin accumulation and coloration.

The Complexity of Modulating Anthocyanin Biosynthesis Pathway by Deficit Irrigation in Table Grapes.

Deficit irrigation (DI) is an irrigation scheduling technique that is used in grapes to improve red color development; however, results are not always satisfactory in table grapes. The red color in grapes is mainly due to the plant pigment anthocyanin. In the present study, the anthocyanin biosynthesis in Scarlet Royal grapes (Vitis vinifera L.) grown in the San Joaquin and Coachella Valleys, and subjected to two different DI strategies was investigated. The objective of this study was to identify potential regulatory factors that may lead to potential treatments to improve red color in table grapes, especially under warm climate conditions. In both locations, DI induced the expression of several genes involved in three major pathways that control the red color in table grapes: anthocyanin biosynthesis, hormone biosynthesis, and antioxidant system. DI at veraison induced anthocyanin accumulation and enhanced red color in berries at harvest time. However, anthocyanin accumulation was lower at the Coachella Valley compared to the San Joaquin Valley. The lower level of anthocyanin was associated with lower expression of critical genes involved in anthocyanin biosynthesis, such as flavonoid-3-O-glucosyltransferase (UFGT), myb-related regulatory gene (R2R3-MYB) (MYBA1), basic helix-loop-helix (bHLH) (MYCA1) and the tryptophan-aspartic acid repeat (WDR or WD40) proteins (WDR1). Further, gene expression analysis revealed the association of ABA biosynthesis gene 9-cis-epoxycarotenoid dioxygenase (NCED1), 1-aminocyclopropane-1-carboxylic acid oxidase (ACO3), and the gibberellic acid (GA) catabolic gene GA2 oxidase (GA2ox1) in the induction of anthocyanin biosynthesis. An increase in the chalcone synthase gene (CHS2) was observed in response to DI treatments in both sites. However, CHS2 expression was higher in Coachella Valley after ending the DI treatment, suggesting the involvement of environmental stress in elevating its transcripts. This data was also supported by the lower level of antioxidant gene expression and enzyme activities in the Coachella Valley compared to the San Joaquin Valley. The present data suggested that the lack of grape red coloration could partially be due to the lower level of antioxidant activities resulting in accelerated anthocyanin degradation and impaired anthocyanin biosynthesis. It seems that under challenging warmer conditions, several factors are required to optimize anthocyanin accumulation via DI, including an active antioxidant system, proper light perception, and hormonal balance.

Maize (Zea mays) seeds can detect above-ground weeds; thiamethoxam alters the view.

BACKGROUND: Far red light is known to penetrate soil and delay seed germination. Thiamethoxam as a seed treatment has been observed to enhance seed germination. No previous work has explored the effect of thiamethoxam on the physiological response of buried maize seed when germinating in the presence of above-ground weeds. We hypothesised that the changes in red:far red reflected from above-ground weeds would be detected by maize seed phytochrome and delay seed germination by decreasing the level of GA and increasing ABA. We further hypothesised that thiamethoxam would overcome this delay in germination. RESULTS: Thiamethoxam enhanced seed germination in the presence of above-ground weeds by increasing GA signalling and downregulating DELLA protein and ABA signalling genes. An increase in amylase activity and a degradation of starch were also observed. CONCLUSIONS: Far red reflected from the above-ground weeds was capable of penetrating below the soil surface and was detected by maize seed phytochrome. Thiamethoxam altered the effect of far red on seed germination by stimulating GA and inhibiting ABA synthesis. This is the first study to suggest that the mode of action of thiamethoxam involves both GA synthesis and ABA inhibition.

Thiamethoxam as a seed treatment alters the physiological response of maize (Zea mays) seedlings to neighbouring weeds.

BACKGROUND: Thiamethoxam is a broad-spectrum neonicotinoid insecticide that, when applied to seed, has been observed to enhance seedling vigour under environmental stress conditions. Stress created by the presence of neighbouring weeds is known to trigger the accumulation of hydrogen peroxide (H2 O2 ) in maize seedling tissue. No previous work has explored the effect of thiamethoxam as a seed treatment on the physiological response of maize seedlings emerging in the presence of neighbouring weeds. RESULTS: Thiamethoxam was found to enhance seedling vigour and to overcome the expression of typical shade avoidance characteristics in the presence of neighbouring weeds. These results were attributed to maintenance of the total phenolics content, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging activity and anthocyanin and lignin contents. These findings were also associated with the activation of scavenging genes, which reduced the accumulation of H2 O2 and the subsequent damage caused by lipid peroxidation in maize seedlings originating from treated seeds even when exposed to neighbouring weeds. CONCLUSIONS: These results suggest the possibility of exploring new chemistries and modes of action as novel seed treatments to upregulate free radical scavenging genes and to maintain the antioxidant system within plants. Such an approach may provide an opportunity to enhance crop competitiveness with weeds.

Control of anthocyanin biosynthesis pathway gene expression by eutypine, a toxin from Eutypa lata, in grape cell tissue cultures.

Eutypine, 4-hydroxy-3-(3-methyl-3-butene-1-ynyl) benzaldehyde, is a toxin produced by Eutypa lata, the causal agent of Eutypa dieback in grapevine. The effect of the toxin on anthocyanin synthesis has been investigated in Vitis vinifera cv. Gamay cell cultures. At concentrations higher than 200 micromol/L, eutypine reduced anthocyanin accumulation in cells. The reduction in anthocyanin accumulation was proportional to the eutypine concentrations and HPLC analysis showed that eutypine affected the levels of all anthocyanins. The effect of eutypine application on the expression of five genes of the anthocyanin biosynthesis pathway, including chalcone synthase (CHS), flavonone-3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), leucoanthocyanidin dioxygenase (LDOX), and UDP glucose-flavonoid 3-O-glucosyl transferase (UFGT) was determined. Expression of CHS, F3H, DFR and LDOXwas not affected by the addition of eutypine to grapevine cell cultures. In contrast, expression of the UFGT gene was dramatically inhibited by the toxin. These results suggest that in grapevine cell cultures, eutypine strongly affects anthocyanin accumulation by inhibiting UFGT gene expression. The mechanism of action of eutypine is discussed.

Similarities between the discovery and regulation of pharmaceuticals and pesticides: in support of a better understanding of the risks and benefits of each.

An argument is presented by which the role of pharmaceuticals and pesticides can both be viewed in terms of contributing to human health. Comparisons are made in terms of discovery and development, regulatory policies and environmental and human impacts. Both technologies target particular biological functions, and in many cases they target similar molecular sites of action. Pharmaceuticals and pesticides undergo a similar registration process; however, both can enter the environment where they can have adverse effects on non-target organisms and, if misused, will have detrimental effects on human health or the environment. It is suggested that the risks associated with the two technologies are similar. The rejection of pesticides by the general public is based primarily on personal value systems and the uncertainty of risk management. It is concluded that plant and animal health are vital to maintaining human health, and that pesticides used in food production are, as with pharmaceuticals, a vital tool used to maintain human health.