High-resolution association mapping with libraries of immortalized lines from ancestral landraces.

Association mapping with immortalized lines of landraces offers several advantages including a high mapping resolution, as demonstrated here in maize by identifying the causal variants underlying QTL for oil content and the metabolite allantoin. Landraces are traditional varieties of crops that present a valuable yet largely untapped reservoir of genetic variation to meet future challenges of agriculture. Here, we performed association mapping in a panel comprising 358 immortalized maize lines from six European Flint landraces.

Engineering of benzoxazinoid biosynthesis in Arabidopsis thaliana: Metabolic and physiological challenges.

Plant specialised metabolites constitute a layer of chemical defence. Classes of the defence compounds are often restricted to a certain taxon of plants, e.g.

A promiscuous beta-glucosidase is involved in benzoxazinoid deglycosylation in Lamium galeobdolon.

In the plant kingdom beta-glucosidases (BGLUs) of the glycosidase hydrolase family 1 have essential function in primary metabolism and are particularly employed in secondary metabolism. They are essential for activation in two-component defence systems based on stabilisation of reactive compounds by glycosylation. Based on de novo assembly we isolated and functionally characterised BGLUs expressed in leaves of Lamium galeobdolon (LgGLUs).

Prolonged expression of the BX1 signature enzyme is associated with a recombination hotspot in the benzoxazinoid gene cluster in Zea mays.

Benzoxazinoids represent preformed protective and allelopathic compounds. The main benzoxazinoid in maize (Zea mays L.) is 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA).

Deducing hybrid performance from parental metabolic profiles of young primary roots of maize by using a multivariate diallel approach.

Heterosis, the greater vigor of hybrids compared to their parents, has been exploited in maize breeding for more than 100 years to produce ever better performing elite hybrids of increased yield. Despite extensive research, the underlying mechanisms shaping the extent of heterosis are not well understood, rendering the process of selecting an optimal set of parental lines tedious. This study is based on a dataset consisting of 112 metabolite levels in young roots of four parental maize inbred lines and their corresponding twelve hybrids, along with the roots' biomass as a heterotic trait.

Chloroplast-localized 6-phosphogluconate dehydrogenase is critical for maize endosperm starch accumulation.

Plants have duplicate versions of the oxidative pentose phosphate pathway (oxPPP) enzymes with a subset localized to the chloroplast. The chloroplast oxPPP provides NADPH and pentose sugars for multiple metabolic pathways. This study identified two loss-of-function alleles of the Zea mays (maize) chloroplast-localized oxPPP enzyme 6-phosphogluconate dehydrogenase (6PGDH).

Comparative analysis of benzoxazinoid biosynthesis in monocots and dicots: independent recruitment of stabilization and activation functions.

Benzoxazinoids represent preformed protective and allelophatic compounds that are found in a multitude of species of the family Poaceae (Gramineae) and occur sporadically in single species of phylogenetically unrelated dicots. Stabilization by glucosylation and activation by hydrolysis is essential for the function of these plant defense compounds. We isolated and functionally characterized from the dicot larkspur (Consolida orientalis) the benzoxazinoid-specific UDP-glucosyltransferase and β-glucosidase that catalyze the enzymatic functions required to avoid autotoxicity and allow activation upon challenge by herbivore and pathogen attack.

Corn hybrids display lower metabolite variability and complex metabolite inheritance patterns.

We conducted a comparative analysis of the root metabolome of six parental maize inbred lines and their 14 corresponding hybrids showing fresh weight heterosis. We demonstrated that the metabolic profiles not only exhibit distinct features for each hybrid line compared with its parental lines, but also separate reciprocal hybrids. Reconstructed metabolic networks, based on robust correlations between metabolic profiles, display a higher network density in most hybrids as compared with the corresponding inbred lines.

Impact of natural genetic variation on the transcriptome of autotetraploid Arabidopsis thaliana.

Polyploidy, the presence of more than two complete sets of chromosomes in an organism, has significantly shaped the genomes of angiosperms during evolution. Two forms of polyploidy are often considered: allopolyploidy, which originates from interspecies hybrids, and autopolyploidy, which originates from intraspecies genome duplication events. Besides affecting genome organization, polyploidy generates other genetic effects.

Plants contain two distinct classes of functional tryptophan synthase beta proteins.

Tryptophan synthase beta-subunits (TSBs) catalyze the last step in tryptophan biosynthesis, i.e. the condensation of indole and serine yielding tryptophan.

Heterotic patterns of sugar and amino acid components in developing maize kernels.

Heterosis is the superior performance of hybrids over their inbred parents. Despite its importance, little is known about the genetic and molecular basis of this phenomenon. Heterosis has been extensively exploited in plant breeding, particularly in maize (Zea mays, L.

Restoring a maize root signal that attracts insect-killing nematodes to control a major pest.

When attacked by herbivorous insects, plants emit volatile compounds that attract natural enemies of the insects. It has been proposed that these volatile signals can be manipulated to improve crop protection. Here, we demonstrate the full potential of this strategy by restoring the emission of a specific belowground signal emitted by insect-damaged maize roots.

Benzoxazinoid biosynthesis, a model for evolution of secondary metabolic pathways in plants.

Benzoxazinoids are secondary metabolites that are effective in defence and allelopathy. They are synthesised in two subfamilies of the Poaceae and sporadically found in single species of the dicots. The biosynthesis is fully elucidated in maize; here the genes encoding the enzymes of the pathway are in physical proximity.

A large number of tetraploid Arabidopsis thaliana lines, generated by a rapid strategy, reveal high stability of neo-tetraploids during consecutive generations.

Arabidopsis thaliana has, in conjunction with A. arenosa, developed into a system for the molecular analysis of alloplolyploidy. However, there are very few Arabidopsis lines available to study autopolyploidy.

Benzoxazinoid biosynthesis in dicot plants.

Benzoxazinoids are common defence compounds of the grasses and are sporadically found in single species of two unrelated orders of the dicots. In the three dicotyledonous species Aphelandra squarrosa, Consolida orientalis and Lamium galeobdolon the main benzoxazinoid aglucon is 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one (DIBOA). While benzoxazinoids in Aphelandra squarrosa are restricted to the root, in Consolida orientalis and Lamium galeobdolon DIBOA is found in all above ground organs of the adult plant in concentrations as high as in the seedling of maize.

Characterisation of the tryptophan synthase alpha subunit in maize.

Background: In bacteria, such as Salmonella typhimurium, tryptophan is synthesized from indole-3-glycerole phosphate (IGP) by a tryptophan synthase alphabetabetaalpha heterotetramer. Plants have evolved multiple alpha (TSA) and beta (TSB) homologs, which have probably diverged in biological function and their ability of subunit interaction. There is some evidence for a tryptophan synthase (TS) complex in Arabidopsis.

Elucidation of the final reactions of DIMBOA-glucoside biosynthesis in maize: characterization of Bx6 and Bx7.

Benzoxazinoids were identified in the early 1960s as secondary metabolites of the grasses that function as natural pesticides and exhibit allelopathic properties. Benzoxazinoids are synthesized in seedlings and stored as glucosides (glcs); the main aglucone moieties are 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one (DIBOA) and 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA). The genes of DIBOA-glc biosynthesis have previously been isolated and the enzymatic functions characterized.

Maize nitrilases have a dual role in auxin homeostasis and beta-cyanoalanine hydrolysis.

The auxin indole-3-acetic acid (IAA), which is essential for plant growth and development, is suggested to be synthesized via several redundant pathways. In maize (Zea mays), the nitrilase ZmNIT2 is expressed in auxin-synthesizing tissues and efficiently hydrolyses indole-3-acetonitrile to IAA. Zmnit2 transposon insertion mutants were compromised in root growth in young seedlings and sensitivity to indole-3-acetonitrile, and accumulated lower quantities of IAA conjugates in kernels and root tips, suggesting a substantial contribution of ZmNIT2 to total IAA biosynthesis in maize.

Robustness of central carbohydrate metabolism in developing maize kernels.

The central carbohydrate metabolism provides the precursors for the syntheses of various storage products in seeds. While the underlying biochemical map is well established, little is known about the organization and flexibility of carbohydrate metabolic fluxes in the face of changing biosynthetic demands or other perturbations. This question was addressed in developing kernels of maize (Zea mays L.

Changes in flux pattern of the central carbohydrate metabolism during kernel development in maize.

Developing kernels of the inbred maize line W22 were grown in sterile culture and supplied with a mixture of [U-13C6]glucose and unlabeled glucose during three consecutive intervals (11-18, 18-25, or 25-32 days after pollination) within the linear phase of starch formation. At the end of each labeling period, glucose was prepared from starch and analyzed by 13C isotope ratio mass spectrometry and high-resolution (13)C NMR spectroscopy. The abundances of individual glucose isotopologs were calculated by computational deconvolution of the NMR data.

On the structural basis of the catalytic mechanism and the regulation of the alpha subunit of tryptophan synthase from Salmonella typhimurium and BX1 from maize, two evolutionarily related enzymes.

Indole is a reaction intermediate in at least two biosynthetic pathways in maize seedlings. In the primary metabolism, the alpha-subunit (TSA) of the bifunctional tryptophan synthase (TRPS) catalyzes the cleavage of indole 3-glycerol phosphate (IGP) to indole and d-glyceraldehyde 3-phosphate (G3P). Subsequently, indole diffuses through the connecting tunnel to the beta-active site where it is condensed with serine to form tryptophan and water.

Evolution of the indole alkaloid biosynthesis in the genus Hordeum: distribution of gramine and DIBOA and isolation of the benzoxazinoid biosynthesis genes from Hordeum lechleri.

Two indole alkaloids with defense related functions are synthesized in the genus Hordeum of the Triticeae. Gramine (3(dimethyl-amino-methyl)-indole) is found in H. spontaneum and in some varieties of H.

Release of the benzoxazinoids defense molecules during lateral- and crown root emergence in Zea mays.

We observed the release of the benzoxazinoids defense molecules on the surface of the primary root and the coleoptilar node in Zea mays during the emergence of lateral- and crown-roots, respectively. At later stages of crown root and lateral root development, benzoxazinoids around the emerged roots were no longer observed. Specific mutants revealed that the developmental status of the emerged roots was not important for the release of benzoxazinoids, but the breakage of the epidermis by emerging roots was.

Transcriptional activation of Igl, the gene for indole formation in Zea mays: a structure-activity study with elicitor-active N-acyl glutamines from insects.

The indole-3-glycerol phosphate lyase Igl is the structural gene of volatile indole biosynthesis in the tritrophic interaction in maize. The gene is activated on transcriptional level with the same kinetics and to the same level by the fatty acid-amino acid conjugates (FAC's) volicitin (17S)-(N-(17-hydroxylinolenoyl)-L-glutamine) and N-linolenoyl-L-glutamine. Both conjugates are present in the regurgitates of herbivorous caterpillars.