אסיף מאגר המחקר החקלאי

Distinct mechanisms of the ORANGE protein in controlling carotenoid flux

Year:

2017

Source of publication :

Authors :

Volume :

173

Co-Authors:

Chayut, N., Department of Vegetable Research, Agricultural Research Organization, Newe Ya’ar Research Center, Ramat Yishay, Israel, Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
Yuan, H., Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, United States
Ohali, S., Department of Vegetable Research, Agricultural Research Organization, Newe Ya’ar Research Center, Ramat Yishay, Israel
Meir, A., Department of Vegetable Research, Agricultural Research Organization, Newe Ya’ar Research Center, Ramat Yishay, Israel
Sa’ar, U., Department of Vegetable Research, Agricultural Research Organization, Newe Ya’ar Research Center, Ramat Yishay, Israel
Tzuri, G., Department of Vegetable Research, Agricultural Research Organization, Newe Ya’ar Research Center, Ramat Yishay, Israel
Zheng, Y., Boyce Thompson Institute, Cornell University, Ithaca, NY, United States
Mazourek, M., Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, United States
Gepstein, S., Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
Zhou, X., Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, United States
Portnoy, V., Department of Vegetable Research, Agricultural Research Organization, Newe Ya’ar Research Center, Ramat Yishay, Israel
Lewinsohn, E., Department of Vegetable Research, Agricultural Research Organization, Newe Ya’ar Research Center, Ramat Yishay, Israel
Schaffer, A.A., Department of Vegetable Research, Agricultural Research Organization, Newe Ya’ar Research Center, Ramat Yishay, Israel, Department of Vegetable Research, Volcani Center, Agricultural Research Organization, Bet Dagan, Israel
Katzir, N., Department of Vegetable Research, Agricultural Research Organization, Newe Ya’ar Research Center, Ramat Yishay, Israel
Fei, Z., Boyce Thompson Institute, Cornell University, Ithaca, NY, United States, United States Department of Agriculture-Agricultural Research Service Robert W. Holley Center for Agriculture and Health, Ithaca, NY, United States
Welsch, R., Faculty of Biology II, University of Freiburg, Freiburg, Germany
Li, L., Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, United States, United States Department of Agriculture-Agricultural Research Service Robert W. Holley Center for Agriculture and Health, Ithaca, NY, United States
Burger, J., Department of Vegetable Research, Agricultural Research Organization, Newe Ya’ar Research Center, Ramat Yishay, Israel
Tadmor, Y., Department of Vegetable Research, Agricultural Research Organization, Newe Ya’ar Research Center, Ramat Yishay, Israel

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Abstract:

β-Carotene adds nutritious value and determines the color of many fruits, including melon (Cucumis melo). In melon mesocarp, β-carotene accumulation is governed by the Orange gene (CmOr) golden single-nucleotide polymorphism (SNP) through a yet to be discovered mechanism. In Arabidopsis (Arabidopsis thaliana), OR increases carotenoid levels by posttranscriptionally regulating phytoene synthase (PSY). Here, we identified a CmOr nonsense mutation (Cmor-lowb) that lowered fruit β-carotene levels with impaired chromoplast biogenesis. Cmor-lowb exerted a minimal effect on PSY transcripts but dramatically decreased PSY protein levels and enzymatic activity, leading to reduced carotenoid metabolic flux and accumulation. However, the golden SNP was discovered to not affect PSY protein levels and carotenoid metabolic flux in melon fruit, as shown by carotenoid and immunoblot analyses of selected melon genotypes and by using chemical pathway inhibitors. The high β-carotene accumulation in golden SNP melons was found to be due to a reduced further metabolism of β-carotene. This was revealed by genetic studies with double mutants including carotenoid isomerase (yofi), a carotenoid-isomerase nonsense mutant, which arrests the turnover of prolycopene. The yofi F2 segregants accumulated prolycopene independently of the golden SNP. Moreover, Cmor-lowb was found to inhibit chromoplast formation and chloroplast disintegration in fruits from 30 d after anthesis until ripening, suggesting that CmOr regulates the chloroplast-to-chromoplast transition. Taken together, our results demonstrate that CmOr is required to achieve PSY protein levels to maintain carotenoid biosynthesis metabolic flux but that the mechanism of the CmOr golden SNP involves an inhibited metabolism downstream of β-carotene to dramatically affect both carotenoid content and plastid fate. © 2017 American Society of Plant Biologists. All rights reserved.

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