An allele of ZmPORB2 encoding a protochlorophyllide oxidoreductase promotes tocopherol accumulation in both leaves and kernels of maize

Summary Phytol is one of the key precursors for tocopherol synthesis in plants, however, the underlying mechanisms concerning the accumulation of tocopherol remain poorly understood. In this study, qVE5, a major QTL affecting tocopherol accumulation in maize kernels was identified via a positional c...

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Published in:	The Plant journal : for cell and molecular biology 2019-10, Vol.100 (1), p.114-127
Main Authors:	Zhan, Wei, Liu, Jie, Pan, Qingchun, Wang, Hong, Yan, Shijuan, Li, Kun, Deng, Min, Li, Wenqiang, Liu, Nannan, Kong, Qian, Fernie, Alisdair R., Yan, Jianbing
Format:	Article
Language:	eng
Subjects:	5' Untranslated Regions Accumulation Association analysis Breeding Chlorophyll Chloroplasts Clonal deletion Cloning Corn Gene deletion Gene polymorphism Gene sequencing Insertion Kernels Leaves maize (Zea mays) Metabolism Metabolites Oxidoreductase Phytol Pollination Polymorphism Precursors Protochlorophyllide QTL mapping Quantitative trait loci Ribonucleic acid RNA Tocopherol Vitamin E ZmPORB2
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Summary:	Summary Phytol is one of the key precursors for tocopherol synthesis in plants, however, the underlying mechanisms concerning the accumulation of tocopherol remain poorly understood. In this study, qVE5, a major QTL affecting tocopherol accumulation in maize kernels was identified via a positional cloning approach. qVE5 encodes a protochlorophyllide oxidoreductase (ZmPORB2), which localizes to the chloroplast. Overexpression of ZmPORB2 increased tocopherol content in both leaves and kernels. Candidate gene association analysis identified a 5/8‐bp insertion/deletion (InDel058) in the 5′ untranslated region (UTR) as the causal polymorphism in affecting ZmPORB2 expression and being highly associated with tocopherol content. We showed that higher expression of ZmPORB2 correlated with more chlorophyll metabolites in the leaf following pollination. RNA‐sequencing and metabolic analysis in near isogenic lines (NILs) support that ZmPORB2 participates in chlorophyll metabolism enabling the production of phytol, an important precursor of tocopherol. We also found that the tocopherol content in the kernel is mainly determined by the maternal genotype, a fact that was further confirmed by in vitro culture experiments. Finally, a PCR‐based marker based on Indel058 was developed in order to facilitate the high tocopherol (vitamin E) maize breeding. Significance Statement Known as vitamin E, tocopherol is a lipid‐soluble antioxidant required for plant growth and human health. In this study, characterization of ZmPORB2 involved in chlorophyll metabolism revealed that this gene affects tocopherol content in maize by the maternal genotype and has applicable potential in breeding.
ISSN:	0960-7412 1365-313X