Granny Smith and Red Delicious are sensitive cultivars to the insurgence of physiological disorders during low temperature storage. The occurrence of necrosis of epidermal cells is described as superficial scald and causes major economic losses to apple growers worldwide. It can arise after prolonged periods of storage at low temperature during shelf life at room temperature. The most common strategies adopted to inhibit scald development in use combine storage in control atmosphere (CA) with treatments with the antioxidant diphenylamine (DPA), or with 1-methylcyclopropene (1-MCP), an inhibitor of ethylene perception. The application of an initial low oxygen stress (ILOS), followed by CA storage is another tool for scald prevention since the use of DPA has been banned in Europe for health concerns in 2011. The high costs of 1-MCP and the request from the organic market sector of a suitable alternative requires more research for ILOS optimisation. Aim of this work is to provide a deeper characterization of the molecular factors putatively associated with superficial scald development. For this purpose, molecular responses to treatment with the ethylene inhibitor 1-MCP, as well as to the application of low and ultra low oxygen storage and wounding were studied to identify factors that may explain the mechanism of action of these preventive treatments in scald prevention. Wounding was applied as a methodological tool with the aim to identify the putative connections between scald incidence and molecular wounding responses as it had been previously shown that wounding inhibits locally apple superficial scald formation. Additionally, the metabolic and molecular responses to low and extreme low oxygen have been characterised and compared with those induced by 1-MCP to highlight ethylene-dependent and ethylene-independent and hypoxia-specific responses. Transcriptional data obtained in the wounding experiment, suggest the existence of at two waves of transcriptional regulation taking place in response to wounding: an early one, most likely linked to the effects of mechanical damage and a later one, taking place after three months of storage, possibly as a consequence of wounding effects. Through the evaluation of the combined effects of wounding and time of storage on transcriptional dynamics it was hypnotized that the priming effect of wounding against scald development may rely on a signalling effect specifically evoked by wounding on ethylene, JA and ABA biosynthesis and signalling pathways. In the time-course experiments exposing apple fruits to different oxygen conditions (normoxia, 21% O2, Nox; hypoxia, 0.8% O2; and extreme hypoxia, 0.4% O2) it was possible to show that the hypoxic stress induced the expression of specific components of the ROP-GAP rheostat in apples skins, in parallel to the up-regulation of NADPH oxidase activity, group VII ERF members and hypoxia marker gene ADH. These events coincided with a general down-regulation of ethylene biosynthetic genes suggesting the existence of a reciprocal regulatory loop involving a negative effect exerted by hypoxia on ethylene responses and signalling proportional to the degree of the hypoxic stress, and, in turn, a repressive effect exerted by ethylene on hypoxic responses. Expression analysis in response to 1-MCP treatment showed that a large part of the hypoxia-dependent DEGs resulted to be significantly and co-ordinately up-regulated in hypoxic conditions and to be either slightly repressed or not regulated at all by 1-MCP treatment. It can be therefore hypothesised that hypoxia induces effects mediated ethylene biosynthesis repression inducing also a large number of hypoxia-specific and ethylene-independent processes. Ethylene and hypoxia were shown to share some regulatory processes acting in concert in the regulation of fermentative pathways, however hypoxia can directly interfere with ethylene’s action changing its signalling upstream of ethylene’s action.

Granny Smith and Red Delicious are sensitive cultivars to the insurgence of physiological disorders during low temperature storage. The occurrence of necrosis of epidermal cells is described as superficial scald and causes major economic losses to apple growers worldwide. It can arise after prolonged periods of storage at low temperature during shelf life at room temperature. The most common strategies adopted to inhibit scald development in use combine storage in control atmosphere (CA) with treatments with the antioxidant diphenylamine (DPA), or with 1-methylcyclopropene (1-MCP), an inhibitor of ethylene perception. The application of an initial low oxygen stress (ILOS), followed by CA storage is another tool for scald prevention since the use of DPA has been banned in Europe for health concerns in 2011. The high costs of 1-MCP and the request from the organic market sector of a suitable alternative requires more research for ILOS optimisation. Aim of this work is to provide a deeper characterization of the molecular factors putatively associated with superficial scald development. For this purpose, molecular responses to treatment with the ethylene inhibitor 1-MCP, as well as to the application of low and ultra low oxygen storage and wounding were studied to identify factors that may explain the mechanism of action of these preventive treatments in scald prevention. Wounding was applied as a methodological tool with the aim to identify the putative connections between scald incidence and molecular wounding responses as it had been previously shown that wounding inhibits locally apple superficial scald formation. Additionally, the metabolic and molecular responses to low and extreme low oxygen have been characterised and compared with those induced by 1-MCP to highlight ethylene-dependent and ethylene-independent and hypoxia-specific responses. Transcriptional data obtained in the wounding experiment, suggest the existence of at two waves of transcriptional regulation taking place in response to wounding: an early one, most likely linked to the effects of mechanical damage and a later one, taking place after three months of storage, possibly as a consequence of wounding effects. Through the evaluation of the combined effects of wounding and time of storage on transcriptional dynamics it was hypnotized that the priming effect of wounding against scald development may rely on a signalling effect specifically evoked by wounding on ethylene, JA and ABA biosynthesis and signalling pathways. In the time-course experiments exposing apple fruits to different oxygen conditions (normoxia, 21% O2, Nox; hypoxia, 0.8% O2; and extreme hypoxia, 0.4% O2) it was possible to show that the hypoxic stress induced the expression of specific components of the ROP-GAP rheostat in apples skins, in parallel to the up-regulation of NADPH oxidase activity, group VII ERF members and hypoxia marker gene ADH. These events coincided with a general down-regulation of ethylene biosynthetic genes suggesting the existence of a reciprocal regulatory loop involving a negative effect exerted by hypoxia on ethylene responses and signalling proportional to the degree of the hypoxic stress, and, in turn, a repressive effect exerted by ethylene on hypoxic responses. Expression analysis in response to 1-MCP treatment showed that a large part of the hypoxia-dependent DEGs resulted to be significantly and co-ordinately up-regulated in hypoxic conditions and to be either slightly repressed or not regulated at all by 1-MCP treatment. It can be therefore hypothesised that hypoxia induces effects mediated ethylene biosynthesis repression inducing also a large number of hypoxia-specific and ethylene-independent processes. Ethylene and hypoxia were shown to share some regulatory processes acting in concert in the regulation of fermentative pathways, however hypoxia can directly interfere with ethylene’s action changing its signalling upstream of ethylene’s action.

Apple Superficial Scald: Identification of physiological and molecular factors / Cainelli, Nadia. - (2022 Mar 30).

Apple Superficial Scald: Identification of physiological and molecular factors

CAINELLI, NADIA
2022

Abstract

Granny Smith and Red Delicious are sensitive cultivars to the insurgence of physiological disorders during low temperature storage. The occurrence of necrosis of epidermal cells is described as superficial scald and causes major economic losses to apple growers worldwide. It can arise after prolonged periods of storage at low temperature during shelf life at room temperature. The most common strategies adopted to inhibit scald development in use combine storage in control atmosphere (CA) with treatments with the antioxidant diphenylamine (DPA), or with 1-methylcyclopropene (1-MCP), an inhibitor of ethylene perception. The application of an initial low oxygen stress (ILOS), followed by CA storage is another tool for scald prevention since the use of DPA has been banned in Europe for health concerns in 2011. The high costs of 1-MCP and the request from the organic market sector of a suitable alternative requires more research for ILOS optimisation. Aim of this work is to provide a deeper characterization of the molecular factors putatively associated with superficial scald development. For this purpose, molecular responses to treatment with the ethylene inhibitor 1-MCP, as well as to the application of low and ultra low oxygen storage and wounding were studied to identify factors that may explain the mechanism of action of these preventive treatments in scald prevention. Wounding was applied as a methodological tool with the aim to identify the putative connections between scald incidence and molecular wounding responses as it had been previously shown that wounding inhibits locally apple superficial scald formation. Additionally, the metabolic and molecular responses to low and extreme low oxygen have been characterised and compared with those induced by 1-MCP to highlight ethylene-dependent and ethylene-independent and hypoxia-specific responses. Transcriptional data obtained in the wounding experiment, suggest the existence of at two waves of transcriptional regulation taking place in response to wounding: an early one, most likely linked to the effects of mechanical damage and a later one, taking place after three months of storage, possibly as a consequence of wounding effects. Through the evaluation of the combined effects of wounding and time of storage on transcriptional dynamics it was hypnotized that the priming effect of wounding against scald development may rely on a signalling effect specifically evoked by wounding on ethylene, JA and ABA biosynthesis and signalling pathways. In the time-course experiments exposing apple fruits to different oxygen conditions (normoxia, 21% O2, Nox; hypoxia, 0.8% O2; and extreme hypoxia, 0.4% O2) it was possible to show that the hypoxic stress induced the expression of specific components of the ROP-GAP rheostat in apples skins, in parallel to the up-regulation of NADPH oxidase activity, group VII ERF members and hypoxia marker gene ADH. These events coincided with a general down-regulation of ethylene biosynthetic genes suggesting the existence of a reciprocal regulatory loop involving a negative effect exerted by hypoxia on ethylene responses and signalling proportional to the degree of the hypoxic stress, and, in turn, a repressive effect exerted by ethylene on hypoxic responses. Expression analysis in response to 1-MCP treatment showed that a large part of the hypoxia-dependent DEGs resulted to be significantly and co-ordinately up-regulated in hypoxic conditions and to be either slightly repressed or not regulated at all by 1-MCP treatment. It can be therefore hypothesised that hypoxia induces effects mediated ethylene biosynthesis repression inducing also a large number of hypoxia-specific and ethylene-independent processes. Ethylene and hypoxia were shown to share some regulatory processes acting in concert in the regulation of fermentative pathways, however hypoxia can directly interfere with ethylene’s action changing its signalling upstream of ethylene’s action.
Apple Superficial Scald: Identification of physiological and molecular factors
30-mar-2022
Granny Smith and Red Delicious are sensitive cultivars to the insurgence of physiological disorders during low temperature storage. The occurrence of necrosis of epidermal cells is described as superficial scald and causes major economic losses to apple growers worldwide. It can arise after prolonged periods of storage at low temperature during shelf life at room temperature. The most common strategies adopted to inhibit scald development in use combine storage in control atmosphere (CA) with treatments with the antioxidant diphenylamine (DPA), or with 1-methylcyclopropene (1-MCP), an inhibitor of ethylene perception. The application of an initial low oxygen stress (ILOS), followed by CA storage is another tool for scald prevention since the use of DPA has been banned in Europe for health concerns in 2011. The high costs of 1-MCP and the request from the organic market sector of a suitable alternative requires more research for ILOS optimisation. Aim of this work is to provide a deeper characterization of the molecular factors putatively associated with superficial scald development. For this purpose, molecular responses to treatment with the ethylene inhibitor 1-MCP, as well as to the application of low and ultra low oxygen storage and wounding were studied to identify factors that may explain the mechanism of action of these preventive treatments in scald prevention. Wounding was applied as a methodological tool with the aim to identify the putative connections between scald incidence and molecular wounding responses as it had been previously shown that wounding inhibits locally apple superficial scald formation. Additionally, the metabolic and molecular responses to low and extreme low oxygen have been characterised and compared with those induced by 1-MCP to highlight ethylene-dependent and ethylene-independent and hypoxia-specific responses. Transcriptional data obtained in the wounding experiment, suggest the existence of at two waves of transcriptional regulation taking place in response to wounding: an early one, most likely linked to the effects of mechanical damage and a later one, taking place after three months of storage, possibly as a consequence of wounding effects. Through the evaluation of the combined effects of wounding and time of storage on transcriptional dynamics it was hypnotized that the priming effect of wounding against scald development may rely on a signalling effect specifically evoked by wounding on ethylene, JA and ABA biosynthesis and signalling pathways. In the time-course experiments exposing apple fruits to different oxygen conditions (normoxia, 21% O2, Nox; hypoxia, 0.8% O2; and extreme hypoxia, 0.4% O2) it was possible to show that the hypoxic stress induced the expression of specific components of the ROP-GAP rheostat in apples skins, in parallel to the up-regulation of NADPH oxidase activity, group VII ERF members and hypoxia marker gene ADH. These events coincided with a general down-regulation of ethylene biosynthetic genes suggesting the existence of a reciprocal regulatory loop involving a negative effect exerted by hypoxia on ethylene responses and signalling proportional to the degree of the hypoxic stress, and, in turn, a repressive effect exerted by ethylene on hypoxic responses. Expression analysis in response to 1-MCP treatment showed that a large part of the hypoxia-dependent DEGs resulted to be significantly and co-ordinately up-regulated in hypoxic conditions and to be either slightly repressed or not regulated at all by 1-MCP treatment. It can be therefore hypothesised that hypoxia induces effects mediated ethylene biosynthesis repression inducing also a large number of hypoxia-specific and ethylene-independent processes. Ethylene and hypoxia were shown to share some regulatory processes acting in concert in the regulation of fermentative pathways, however hypoxia can directly interfere with ethylene’s action changing its signalling upstream of ethylene’s action.
Apple Superficial Scald: Identification of physiological and molecular factors / Cainelli, Nadia. - (2022 Mar 30).
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