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Reduction of photosynthetic sensitivity in response to abiotic stress in tomato is mediated by a new generation plant activator.

Wargent JJ, Pickup DA, Paul ND, Roberts MR - BMC Plant Biol. (2013)

Bottom Line: Yield losses as a result of abiotic stress factors present a significant challenge for the future of global food production.Salinity treatment led to a maximal 47% reduction in net photosynthetic rate 8 d following NaCl treatment, yet in Alethea pre-treated seedlings, sensitivity to salinity stress was markedly reduced during the experimental period.Alethea affected the expression of genes related to biotic stress, ethylene signalling, cell wall synthesis, redox signalling and photosynthetic processes.

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ABSTRACT

Background: Yield losses as a result of abiotic stress factors present a significant challenge for the future of global food production. While breeding technologies provide potential to combat negative stress-mediated outcomes over time, interventions which act to prime plant tolerance to stress, via the use of phytohormone-based elicitors for example, could act as a valuable tool for crop protection. However, the translation of fundamental biology into functioning solution is often constrained by knowledge-gaps.

Results: Photosynthetic and transcriptomic responses were characterised in young tomato (Solanum lycopersicum L.) seedlings in response to pre-treatment with a new plant health activator technology, 'Alethea', followed by a subsequent 100 mM salinity stress. Alethea is a novel proprietary technology composed of three key constituent compounds; the hitherto unexplored compound potassium dihydrojasmonate, an analogue of jasmonic acid; sodium benzoate, a carboxylic acid precursor to salicylic acid, and the α-amino acid L-arginine. Salinity treatment led to a maximal 47% reduction in net photosynthetic rate 8 d following NaCl treatment, yet in Alethea pre-treated seedlings, sensitivity to salinity stress was markedly reduced during the experimental period. Microarray analysis of leaf transcriptional responses showed that while salinity stress and Alethea individually impacted on largely non-overlapping, distinct groups of genes, Alethea pre-treatment substantially modified the response to salinity. Alethea affected the expression of genes related to biotic stress, ethylene signalling, cell wall synthesis, redox signalling and photosynthetic processes. Since Alethea had clear effects on photosynthesis/chloroplastic function at the physiological and molecular levels, we also investigated the ability of Alethea to protect various crop species against methyl viologen, a potent generator of oxidative stress in chloroplasts. Alethea pre-treatment produced dramatic reductions in visible foliar necrosis caused by methyl viologen compared with non-primed controls.

Conclusions: 'Alethea' technology mediates positive recovery of abiotic stress-induced photosynthetic and foliar loss of performance, which is accompanied by altered transcriptional responses to stress.

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Effects of Alethea and salinity on proline and polyamine biosynthesis. Pathway diagram illustrating conversion of arginine and glutamate to ornithine and thence proline. Significant transcriptional effects of Alethea and salinity on genes encoding relevant enzymes (italics) are shown as red arrows for up-regulation and blue bars for down-regulation.
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Figure 8: Effects of Alethea and salinity on proline and polyamine biosynthesis. Pathway diagram illustrating conversion of arginine and glutamate to ornithine and thence proline. Significant transcriptional effects of Alethea and salinity on genes encoding relevant enzymes (italics) are shown as red arrows for up-regulation and blue bars for down-regulation.

Mentions: This mechanism would be expected to provide protection of photosynthesis under a range of abiotic stresses. This was confirmed using methyl viologen to generate chloroplast oxidative stress (Figure 6). Consistent with this, the ability of SA and JA to protect plants against salinity and other abiotic stresses has been suggested to result at least in part, from an up-regulation of antioxidative biochemistry [34,52-54]. Arginine (Arg), the third active ingredient in Alethea, has also been shown to activate antioxidant enzyme activity in tomato fruit, and exogenous application of Arg provided protection against chilling stress [55]. One explanation for the effect of Arg on antioxidant activity is its role in polyamine metabolism, where both Arg and its derivative, ornithine, are substrates for polyamine synthesis (Figure 8) [56]. Polyamines have been proposed to play important roles in abiotic stress tolerance, including via direct and indirect effects on antioxidants [57]. Ornithine also acts as a precursor for proline biosynthesis, which is also a component of drought and salinity tolerance. Our microarray analysis identified several changes in gene expression which point to a role for Alethea in the up-regulation of proline and perhaps also polyamine biosynthesis. Genes encoding arginase and acetylornithine deacetylase, enzymes for ornithine biosynthesis, were up-regulated by Alethea and salt respectively, implying increased ornithine biosynthesis, whilst proline oxidase was strongly down-regulated by salinity, consistent with an increase in proline accumulation; these events are summarised in Figure 8. Moreover, arginase gene expression has previously been shown to be responsive to both application of exogenous Arg and JA [54,56].


Reduction of photosynthetic sensitivity in response to abiotic stress in tomato is mediated by a new generation plant activator.

Wargent JJ, Pickup DA, Paul ND, Roberts MR - BMC Plant Biol. (2013)

Effects of Alethea and salinity on proline and polyamine biosynthesis. Pathway diagram illustrating conversion of arginine and glutamate to ornithine and thence proline. Significant transcriptional effects of Alethea and salinity on genes encoding relevant enzymes (italics) are shown as red arrows for up-regulation and blue bars for down-regulation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3733976&req=5

Figure 8: Effects of Alethea and salinity on proline and polyamine biosynthesis. Pathway diagram illustrating conversion of arginine and glutamate to ornithine and thence proline. Significant transcriptional effects of Alethea and salinity on genes encoding relevant enzymes (italics) are shown as red arrows for up-regulation and blue bars for down-regulation.
Mentions: This mechanism would be expected to provide protection of photosynthesis under a range of abiotic stresses. This was confirmed using methyl viologen to generate chloroplast oxidative stress (Figure 6). Consistent with this, the ability of SA and JA to protect plants against salinity and other abiotic stresses has been suggested to result at least in part, from an up-regulation of antioxidative biochemistry [34,52-54]. Arginine (Arg), the third active ingredient in Alethea, has also been shown to activate antioxidant enzyme activity in tomato fruit, and exogenous application of Arg provided protection against chilling stress [55]. One explanation for the effect of Arg on antioxidant activity is its role in polyamine metabolism, where both Arg and its derivative, ornithine, are substrates for polyamine synthesis (Figure 8) [56]. Polyamines have been proposed to play important roles in abiotic stress tolerance, including via direct and indirect effects on antioxidants [57]. Ornithine also acts as a precursor for proline biosynthesis, which is also a component of drought and salinity tolerance. Our microarray analysis identified several changes in gene expression which point to a role for Alethea in the up-regulation of proline and perhaps also polyamine biosynthesis. Genes encoding arginase and acetylornithine deacetylase, enzymes for ornithine biosynthesis, were up-regulated by Alethea and salt respectively, implying increased ornithine biosynthesis, whilst proline oxidase was strongly down-regulated by salinity, consistent with an increase in proline accumulation; these events are summarised in Figure 8. Moreover, arginase gene expression has previously been shown to be responsive to both application of exogenous Arg and JA [54,56].

Bottom Line: Yield losses as a result of abiotic stress factors present a significant challenge for the future of global food production.Salinity treatment led to a maximal 47% reduction in net photosynthetic rate 8 d following NaCl treatment, yet in Alethea pre-treated seedlings, sensitivity to salinity stress was markedly reduced during the experimental period.Alethea affected the expression of genes related to biotic stress, ethylene signalling, cell wall synthesis, redox signalling and photosynthetic processes.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Background: Yield losses as a result of abiotic stress factors present a significant challenge for the future of global food production. While breeding technologies provide potential to combat negative stress-mediated outcomes over time, interventions which act to prime plant tolerance to stress, via the use of phytohormone-based elicitors for example, could act as a valuable tool for crop protection. However, the translation of fundamental biology into functioning solution is often constrained by knowledge-gaps.

Results: Photosynthetic and transcriptomic responses were characterised in young tomato (Solanum lycopersicum L.) seedlings in response to pre-treatment with a new plant health activator technology, 'Alethea', followed by a subsequent 100 mM salinity stress. Alethea is a novel proprietary technology composed of three key constituent compounds; the hitherto unexplored compound potassium dihydrojasmonate, an analogue of jasmonic acid; sodium benzoate, a carboxylic acid precursor to salicylic acid, and the α-amino acid L-arginine. Salinity treatment led to a maximal 47% reduction in net photosynthetic rate 8 d following NaCl treatment, yet in Alethea pre-treated seedlings, sensitivity to salinity stress was markedly reduced during the experimental period. Microarray analysis of leaf transcriptional responses showed that while salinity stress and Alethea individually impacted on largely non-overlapping, distinct groups of genes, Alethea pre-treatment substantially modified the response to salinity. Alethea affected the expression of genes related to biotic stress, ethylene signalling, cell wall synthesis, redox signalling and photosynthetic processes. Since Alethea had clear effects on photosynthesis/chloroplastic function at the physiological and molecular levels, we also investigated the ability of Alethea to protect various crop species against methyl viologen, a potent generator of oxidative stress in chloroplasts. Alethea pre-treatment produced dramatic reductions in visible foliar necrosis caused by methyl viologen compared with non-primed controls.

Conclusions: 'Alethea' technology mediates positive recovery of abiotic stress-induced photosynthetic and foliar loss of performance, which is accompanied by altered transcriptional responses to stress.

Show MeSH
Related in: MedlinePlus