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Light regulation of chlorophyll and glycoalkaloid biosynthesis during tuber greening of potato S. tuberosum

Light regulation of chlorophyll and glycoalkaloid biosynthesis during tuber greening of potato S. tuberosum
Light regulation of chlorophyll and glycoalkaloid biosynthesis during tuber greening of potato S. tuberosum

Potato, S. tuberosum, is one of the most important global crops, but has high levels of waste due to tuber greening under light, which is associated with the accumulation of neurotoxic glycoalkaloids. However, unlike the situation in de-etiolating seedlings, the mechanisms underlying tuber greening are not well understood. Here, we have investigated the effect of monochromatic blue, red, and far-red light on the regulation of chlorophyll and glycoalkaloid accumulation in potato tubers. Blue and red wavelengths were effective for induction and accumulation of chlorophyll, carotenoids and the two major potato glycoalkaloids, α-solanine and α-chaconine, whereas none of these accumulated in darkness or under far-red light. Key genes in chlorophyll biosynthesis (HEMA1, encoding the rate-limiting enzyme glutamyl-tRNA reductase, GSA, CHLH and GUN4) and six genes (HMG1, SQS, CAS1, SSR2, SGT1 and SGT2) required for glycoalkaloid synthesis were also induced under white, blue, and red light but not in darkness or under far-red light. These data suggest a role for both cryptochrome and phytochrome photoreceptors in chlorophyll and glycoalkaloid accumulation. The contribution of phytochrome was further supported by the observation that far-red light could inhibit white light-induced chlorophyll and glycoalkaloid accumulation and associated gene expression. Transcriptomic analysis of tubers exposed to white, blue, and red light showed that light induction of photosynthesis and tetrapyrrole-related genes grouped into three distinct groups with one group showing a generally progressive induction by light at both 6 h and 24 h, a second group showing induction at 6 h in all light treatments, but induction only by red and white light at 24 h and a third showing just a very moderate light induction at 6 h which was reduced to the dark control level at 24 h. All glycoalkaloid synthesis genes showed a group one profile consistent with what was seen for the most light regulated chlorophyll synthesis genes. Our data provide a molecular framework for developing new approaches to reducing waste due to potato greening.

King Edward (KE), S. tuberosum, blue light, chlorophyll, glycoalkaloid, red/far-red light
1664-462X
1-19
Okamoto, Haruko
cea35380-7618-44c8-a268-47b0198cc7f9
Ducreux, Laurence J.M.
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Allwood, J. William
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Hedley, Pete E.
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Wright, Alison
158f7014-ab90-408e-94b1-49bcd2ca8ceb
Gururajan, Vidyanath
fdb24e28-238d-42f6-9677-42c5ce12ae06
Terry, Matthew J.
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Taylor, Mark A.
79d9666a-da02-41ca-b850-f1c7ac3d6846
Okamoto, Haruko
cea35380-7618-44c8-a268-47b0198cc7f9
Ducreux, Laurence J.M.
1c95923e-9440-4397-8476-c9ebbf201ff1
Allwood, J. William
d91bcba2-7973-4c65-a0ca-d5ba2c9dee55
Hedley, Pete E.
4cbbf36c-e468-4847-84ae-bb77655e41c8
Wright, Alison
158f7014-ab90-408e-94b1-49bcd2ca8ceb
Gururajan, Vidyanath
fdb24e28-238d-42f6-9677-42c5ce12ae06
Terry, Matthew J.
a8c2cd6b-8d35-4053-8d77-3841c2427c3b
Taylor, Mark A.
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Okamoto, Haruko, Ducreux, Laurence J.M., Allwood, J. William, Hedley, Pete E., Wright, Alison, Gururajan, Vidyanath, Terry, Matthew J. and Taylor, Mark A. (2020) Light regulation of chlorophyll and glycoalkaloid biosynthesis during tuber greening of potato S. tuberosum. Frontiers in Plant Science, 11, 1-19, [753]. (doi:10.3389/fpls.2020.00753).

Record type: Article

Abstract

Potato, S. tuberosum, is one of the most important global crops, but has high levels of waste due to tuber greening under light, which is associated with the accumulation of neurotoxic glycoalkaloids. However, unlike the situation in de-etiolating seedlings, the mechanisms underlying tuber greening are not well understood. Here, we have investigated the effect of monochromatic blue, red, and far-red light on the regulation of chlorophyll and glycoalkaloid accumulation in potato tubers. Blue and red wavelengths were effective for induction and accumulation of chlorophyll, carotenoids and the two major potato glycoalkaloids, α-solanine and α-chaconine, whereas none of these accumulated in darkness or under far-red light. Key genes in chlorophyll biosynthesis (HEMA1, encoding the rate-limiting enzyme glutamyl-tRNA reductase, GSA, CHLH and GUN4) and six genes (HMG1, SQS, CAS1, SSR2, SGT1 and SGT2) required for glycoalkaloid synthesis were also induced under white, blue, and red light but not in darkness or under far-red light. These data suggest a role for both cryptochrome and phytochrome photoreceptors in chlorophyll and glycoalkaloid accumulation. The contribution of phytochrome was further supported by the observation that far-red light could inhibit white light-induced chlorophyll and glycoalkaloid accumulation and associated gene expression. Transcriptomic analysis of tubers exposed to white, blue, and red light showed that light induction of photosynthesis and tetrapyrrole-related genes grouped into three distinct groups with one group showing a generally progressive induction by light at both 6 h and 24 h, a second group showing induction at 6 h in all light treatments, but induction only by red and white light at 24 h and a third showing just a very moderate light induction at 6 h which was reduced to the dark control level at 24 h. All glycoalkaloid synthesis genes showed a group one profile consistent with what was seen for the most light regulated chlorophyll synthesis genes. Our data provide a molecular framework for developing new approaches to reducing waste due to potato greening.

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fpls-11-00753 - Version of Record
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Accepted/In Press date: 12 May 2020
e-pub ahead of print date: 30 June 2020
Published date: 2020
Keywords: King Edward (KE), S. tuberosum, blue light, chlorophyll, glycoalkaloid, red/far-red light

Identifiers

Local EPrints ID: 443369
URI: http://eprints.soton.ac.uk/id/eprint/443369
ISSN: 1664-462X
PURE UUID: 901f3b25-c2d2-420a-9744-eff476c02ce2
ORCID for Matthew J. Terry: ORCID iD orcid.org/0000-0001-5002-2708

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Date deposited: 21 Aug 2020 16:31
Last modified: 26 Nov 2021 02:38

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Contributors

Author: Haruko Okamoto
Author: Laurence J.M. Ducreux
Author: J. William Allwood
Author: Pete E. Hedley
Author: Alison Wright
Author: Vidyanath Gururajan
Author: Mark A. Taylor

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