Decreased Protein Abundance of Lycopene β-Cyclase Contributes to Red Flesh in Domesticated Watermelon1
The gene ClLCYB contributes to the red flesh color of domesticated watermelon through decreased protein level to convert lycopene to β-carotene in the carotenogenesis pathway. Red-fleshed watermelons ( Citrullus lanatus ) that accumulate lycopene in their flesh cells have been selected and domestica...
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Published in | Plant physiology (Bethesda) Vol. 183; no. 3; pp. 1171 - 1183 |
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Main Authors | , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
American Society of Plant Biologists
22.04.2020
|
Online Access | Get full text |
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Summary: | The gene ClLCYB contributes to the red flesh color of domesticated watermelon through decreased protein level to convert lycopene to β-carotene in the carotenogenesis pathway.
Red-fleshed watermelons (
Citrullus lanatus
) that accumulate lycopene in their flesh cells have been selected and domesticated from their pale-fleshed ancestors. However, the molecular basis of this trait remains poorly understood. Using map-based cloning and transgenic analysis, we identified a lycopene β-cyclase (
ClLCYB
) gene that controls the flesh color of watermelon. Down-regulation of
ClLCYB
caused the flesh color to change from pale yellow to red, and
ClLCYB
overexpression in the red-fleshed line caused the flesh color to change to orange. Analysis of
ClLCYB
single-nucleotide polymorphisms using 211 watermelon accessions with different flesh colors revealed that two missense mutations between three haplotypes (
ClLCYB
red
,
ClLCYB
white
, and
ClLCYB
yellow
) were selected and largely fixed in domesticated watermelon. Proteins derived from these three
ClLCYB
haplotypes were localized in plastids to catalyze the conversion of lycopene to β-carotene and showed similar catalytic abilities. We revealed that ClLCYB protein abundance, instead of
ClLCYB
transcript level, was negatively correlated with lycopene accumulation. Different amounts of ClLCYB protein degradation among the
ClLCYB
haplotypes were found in ClLCYB transgenic Arabidopsis (
Arabidopsis thaliana
) lines. After treatment with the proteasome inhibitor MG132, the concentration of ClLCYB
red
increased noticeably compared with other ClLCYB proteins. These results indicate that natural missense mutations within
ClLCYB
influence ClLCYB protein abundance and have contributed to the development of red flesh color in domesticated watermelon. |
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Bibliography: | J.Z. performed most of the experiments and contributed to the writing; H.S. and S.G. performed most of the bioinformatics analysis; Y.R., M.L., and J.W. provided technical assistance to J.Z.; H.Z. and G.G. supervised the experiments; Y.X. managed the study. Senior author. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Yong Xu (xuyong@nercv.org). www.plantphysiol.org/cgi/doi/10.1104/pp.19.01409 |
ISSN: | 0032-0889 1532-2548 |
DOI: | 10.1104/pp.19.01409 |