RESUMO
Carotenoids perform a broad range of important functions in humans; therefore, carotenoid biofortification of maize (Zea mays L.), one of the most highly produced cereal crops worldwide, would have a global impact on human health. PLASTID TERMINAL OXIDASE (PTOX) genes play an important role in carotenoid metabolism; however, the possible function of PTOX in carotenoid biosynthesis in maize has not yet been explored. In this study, we characterized the maize PTOX locus by forward- and reverse-genetic analyses. While most higher plant species possess a single copy of the PTOX gene, maize carries two tandemly duplicated copies. Characterization of mutants revealed that disruption of either copy resulted in a carotenoid-deficient phenotype. We identified mutations in the PTOX genes as being causal of the classic maize mutant, albescent1. Remarkably, overexpression of ZmPTOX1 significantly improved the content of carotenoids, especially ß-carotene (provitamin A), which was increased by ~threefold, in maize kernels. Overall, our study shows that maize PTOX locus plays an important role in carotenoid biosynthesis in maize kernels and suggests that fine-tuning the expression of this gene could improve the nutritional value of cereal grains.
Assuntos
Oxirredutases , Zea mays , Humanos , Oxirredutases/genética , Oxirredutases/metabolismo , Zea mays/genética , Zea mays/metabolismo , Carotenoides/metabolismo , beta Caroteno/metabolismo , Grão Comestível/genética , Grão Comestível/metabolismo , Plastídeos/genética , Plastídeos/metabolismoRESUMO
Since its 2015 update, MaizeGDB, the Maize Genetics and Genomics database, has expanded to support the sequenced genomes of many maize inbred lines in addition to the B73 reference genome assembly. Curation and development efforts have targeted high quality datasets and tools to support maize trait analysis, germplasm analysis, genetic studies, and breeding. MaizeGDB hosts a wide range of data including recent support of new data types including genome metadata, RNA-seq, proteomics, synteny, and large-scale diversity. To improve access and visualization of data types several new tools have been implemented to: access large-scale maize diversity data (SNPversity), download and compare gene expression data (qTeller), visualize pedigree data (Pedigree Viewer), link genes with phenotype images (MaizeDIG), and enable flexible user-specified queries to the MaizeGDB database (MaizeMine). MaizeGDB also continues to be the community hub for maize research, coordinating activities and providing technical support to the maize research community. Here we report the changes MaizeGDB has made within the last three years to keep pace with recent software and research advances, as well as the pan-genomic landscape that cheaper and better sequencing technologies have made possible. MaizeGDB is accessible online at https://www.maizegdb.org.
Assuntos
Biologia Computacional/métodos , Bases de Dados Genéticas , Genoma de Planta/genética , Genômica/métodos , Zea mays/genética , Regulação da Expressão Gênica de Plantas , Variação Genética , Armazenamento e Recuperação da Informação/métodos , Internet , Polimorfismo de Nucleotídeo Único , Proteômica/métodos , Interface Usuário-Computador , Zea mays/metabolismoRESUMO
Maize white seedling 3 (w3) has been used to study carotenoid deficiency for almost 100 years, although the molecular basis of the mutation has remained unknown. Here we show that the w3 phenotype is caused by disruption of the maize gene for homogentisate solanesyl transferase (HST), which catalyzes the first and committed step in plastoquinone-9 (PQ-9) biosynthesis in the plastid. The resulting PQ-9 deficiency prohibits photosynthetic electron transfer and eliminates PQ-9 as an oxidant in the enzymatic desaturation of phytoene during carotenoid synthesis. As a result, light-grown w3 seedlings are albino, deficient in colored carotenoids and accumulate high levels of phytoene. However, despite the absence of PQ-9 for phytoene desaturation, dark-grown w3 seedlings can produce abscisic acid (ABA) and homozygous w3 kernels accumulate sufficient carotenoids to generate ABA needed for seed maturation. The presence of ABA and low levels of carotenoids in w3 nulls indicates that phytoene desaturase is able to use an alternate oxidant cofactor, albeit less efficiently than PQ-9. The observation that tocopherols and tocotrienols are modestly affected in w3 embryos and unaffected in w3 endosperm indicates that, unlike leaves, grain tissues deficient in PQ-9 are not subject to severe photo-oxidative stress. In addition to identifying the molecular basis for the maize w3 mutant, we: (1) show that low levels of phytoene desaturation can occur in w3 seedlings in the absence of PQ-9; and (2) demonstrate that PQ-9 and carotenoids are not required for vitamin E accumulation.
Assuntos
Alquil e Aril Transferases/metabolismo , Proteínas de Plantas/metabolismo , Plastoquinona/metabolismo , Tocoferóis/metabolismo , Zea mays/metabolismo , Ácido Abscísico/metabolismo , Alquil e Aril Transferases/genética , Carotenoides/genética , Carotenoides/metabolismo , Mutação , Oxirredutases/genética , Oxirredutases/metabolismo , Fenótipo , Fotossíntese , Filogenia , Folhas de Planta/genética , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Plastídeos/genética , Plastídeos/metabolismo , Sementes/genética , Sementes/metabolismo , Vitamina E/genética , Vitamina E/metabolismo , Zea mays/genéticaRESUMO
The maize (Zea mays) opaque5 (o5) locus was shown to encode the monogalactosyldiacylglycerol synthase MGD1. Null and point mutations of o5 that affect the vitreous nature of mature endosperm engendered an allelic series of lines with stepwise reductions in gene function. C(18:3)/C(18:2) galactolipid abundance in seedling leaves was reduced proportionally, without significant effects on total galactolipid content. This alteration in polar lipid composition disrupted the organization of thylakoid membranes into granal stacks. Total galactolipid abundance in endosperm was strongly reduced in o5(-) mutants, causing developmental defects and changes in starch production such that the normal simple granules were replaced with compound granules separated by amyloplast membrane. Complete loss of MGD1 function in a null mutant caused kernel lethality owing to failure in both endosperm and embryo development. The data demonstrate that low-abundance galactolipids with five double bonds serve functions in plastid membranes that are not replaced by the predominant species with six double bonds. Furthermore, the data identify a function of amyloplast membranes in the development of starch granules. Finally, the specific changes in lipid composition suggest that MGD1 can distinguish the constituency of acyl groups on its diacylglycerol substrate based upon the degree of desaturation.
Assuntos
Cloroplastos/metabolismo , Galactolipídeos , Galactosiltransferases/metabolismo , Proteínas de Plantas/metabolismo , Plastídeos/metabolismo , Zea mays/química , Zea mays/enzimologia , Alelos , Amilopectina/química , Amilopectina/metabolismo , Cloroplastos/química , Cloroplastos/ultraestrutura , Endosperma/química , Endosperma/metabolismo , Galactolipídeos/química , Galactolipídeos/metabolismo , Galactosiltransferases/genética , Dados de Sequência Molecular , Mutação , Filogenia , Folhas de Planta/química , Folhas de Planta/genética , Folhas de Planta/metabolismo , Proteínas de Plantas/classificação , Proteínas de Plantas/genética , Plastídeos/química , Plastídeos/ultraestrutura , Plântula/anatomia & histologia , Plântula/genética , Plântula/metabolismo , Amido/biossíntese , Zea mays/anatomia & histologia , Zea mays/fisiologiaRESUMO
We describe a family of 3 dominant r1 haplotype-specific enhancers of aleurone color in Zea mays. Stable alleles of the 3 enhancement of r1 loci (enr1, enr2, and enr3) intensify aleurone color conferred by certain pale and near-colorless r1 haplotypes. In addition, unstable alleles of enr1 act on the same set of r1 haplotypes, producing spotted kernels. Components of this instability cross react with the Fcu system of instability. Two of the enr loci are linked with one another but none of the 3 are linked with r1. The r1 haplotypes affected by enr alleles overlap those affected by the inr family of r1 haplotype-specific inhibitors of aleurone color, suggesting a possible interaction.
Assuntos
Cor , Genes de Plantas , Haplótipos , Pigmentação/genética , Zea mays/genética , Mapeamento Cromossômico , Cromossomos de Plantas , Cruzamentos Genéticos , Elementos de DNA Transponíveis/fisiologia , Epistasia Genética , Ligação Genética , Modelos Biológicos , Mutagênese Insercional/genética , Mutagênese Insercional/fisiologia , Plantas Geneticamente Modificadas , Locos de Características Quantitativas/genéticaRESUMO
The Spotted-dilute controlling element system in maize involves an autonomous Spotting factor (Spf), and a receptor at the r1 locus haplotype R1-r(spotted dilute2). Its relationship with other maize transposable element systems is poorly characterized. Through development of a genetic tester that carries receptors for both the Spotted-dilute and the En/Spm controlling element systems, we determined that both receptors respond equally to Spf and En/Spm and that Spf is therefore a member of the En/Spm family of controlling elements.