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

Abstract

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.

RETRACTED ARTICLE: Light Harvesting-like Protein 3 Interacts with Phytoene Synthase and Is Necessary for Carotenoid and Chlorophyll Biosynthesis in Rice

“…The repressed protein abundances of PORB and GGR enzymes lead to lower levels of chlorophyll contents and subsequently caused yellow leaf phenotype in several studies (Kimura et al 2018;Li et al 2019;Buhr et al 2017;Liu et al 2015). On the other hand, overexpression of PORB produces more chlorophyll metabolites in plant leaves (Zhan et al 2019) and overexpression of GGR also generates more contents of chlorophylls in tomato leaves (Liu et al 2015). The chlorophyll contents are reduced in oslil3 mutant that is in accordance with the lower accumulation levels of PORB and GGR protein in this mutant.…”

Benefiting others and self: Production of vitamins in plants

“…The development of next‐generation sequencing technologies and genome editing technology such as clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR‐associated protein 9 (Cas9) strategy (Chen et al, 2019) have largely accelerated crop genetic improvement. Efforts have been done to elevate crop yield by knocking out repressors, such as grain number ( OsGn1a) , grain size ( OsGS3 ), grain weight ( OsGW5 , TaGW2 ), panicle size ( OsDEP1 ), and tiller number ( OsAAP3 ) (Li et al, 2016a; Liu et al, 2017; Lu et al, 2018; Zhang et al, 2018), and to enhance plant resistance to biotic stresses, such as powdery mildew in wheat and tomato (Wang et al, 2014; Nekrasov et al, 2017), and blast (Wang et al, 2016) and bacterial blight (Zhou et al, 2015) in rice. In addition, CRISPR/Cas9 has been used to improve quality of crops, such as rice with high‐amylose and resistant starch (Sun et al, 2017), Camelina sativa (Jiang et al, 2017; Morineau et al, 2017) and Brassica napus (Okuzaki et al, 2018) with high oleic acid oil, tomato with enhanced lycopene (Li et al, 2018d) or γ‐aminobutyric acid (GABA) content (Nonaka et al, 2017; Li et al, 2018b), and potato (hairy roots) with less toxic steroidal glycoalkaloids (Nakayasu et al, 2018).…”

“…An alternative pathway of phosphorylation of free phytol to (phytyl-P) and phytyl-PP has been described (Ischebeck et al, 2006;Valentin et al, 2006). Free phytol derives from chlorophyll degradation (Schelbert et al, 2009;Zhan et al, 2019). Afterward, kinases phosphorylate phytol to phytyl monophosphate and phytyl-PP.…”

“…This links phytol release from chlorophyll with tocopherol production, and deepens our knowledge about vitamin E synthesis ( Figure 2B). Recently, Zhan et al, (2019) found that an allele of ZmPORB2 participates in chlorophyll metabolism, enabling the production of phytol, which promotes tocopherol accumulation in both the leaves and kernels of maize. In addition, a geranylgeranyl reductase (OsGGR2) was identified, which is responsible for the formation either of phytyl-PP from GGDP or of chlorophyll from geranylgeranyl chlorophyll, thus determining tocotrienol/tocopherol production (Kimura et al, 2018).…”

Identification of quantitative trait loci for increased α-tocopherol biosynthesis in wild soybean using a high-density genetic map

“…As well as those in tocopherol biosynthesis pathways, novel genes also exhibit an association with contents of γ-Toc, δ-Toc, and total Toc, including two genes for protochlorophyllide reductase in chlorophyll biosynthesis and a gene for long-chain acyl-coenzyme A synthase in the fatty acid pathway of maize [40, 41]. Recently, a candidate gene association analysis showed that a 5/8-bp insertion/deletion in promoter region of ZmPORB2 encoding a protochlorophyllide oxidoreductase is related to total tocopherol content in maize [50].…”