Magnesium and calcium overaccumulate in the leaves of a schengen3 mutant of Brassica rapa.

Magnesium (Mg) and calcium (Ca) are essential mineral nutrients poorly supplied in many human food systems. In grazing livestock, Mg and Ca deficiencies are costly welfare issues. Here, we report a Brassica rapa loss-of-function schengen3 (sgn3) mutant, braA.sgn3.a-1, which accumulates twice as much Mg and a third more Ca in its leaves. We mapped braA.sgn3.a to a single recessive locus using a forward ionomic screen of chemically mutagenized lines with subsequent backcrossing and linked-read sequencing of second back-crossed, second filial generation (BC2F2) segregants. Confocal imaging revealed a disrupted root endodermal diffusion barrier, consistent with SGN3 encoding a receptor-like kinase required for normal formation of Casparian strips, as reported in thale cress (Arabidopsis thaliana). Analysis of the spatial distribution of elements showed elevated extracellular Mg concentrations in leaves of braA.sgn3.a-1, hypothesized to result from preferential export of excessive Mg from cells to ensure suitable cellular concentrations. This work confirms a conserved role of SGN3 in controlling nutrient homeostasis in B. rapa, and reveals mechanisms by which plants are able to deal with perturbed shoot element concentrations resulting from a "leaky" root endodermal barrier. Characterization of variation in leaf Mg and Ca accumulation across a mutagenized population of B. rapa shows promise for using such populations in breeding programs to increase edible concentrations of essential human and animal nutrients.

Accelerating root system phenotyping of seedlings through a computer-assisted processing pipeline.

BACKGROUND: There are numerous systems and techniques to measure the growth of plant roots. However, phenotyping large numbers of plant roots for breeding and genetic analyses remains challenging. One major difficulty is to achieve high throughput and resolution at a reasonable cost per plant sample. Here we describe a cost-effective root phenotyping pipeline, on which we perform time and accuracy benchmarking to identify bottlenecks in such pipelines and strategies for their acceleration. RESULTS: Our root phenotyping pipeline was assembled with custom software and low cost material and equipment. Results show that sample preparation and handling of samples during screening are the most time consuming task in root phenotyping. Algorithms can be used to speed up the extraction of root traits from image data, but when applied to large numbers of images, there is a trade-off between time of processing the data and errors contained in the database. CONCLUSIONS: Scaling-up root phenotyping to large numbers of genotypes will require not only automation of sample preparation and sample handling, but also efficient algorithms for error detection for more reliable replacement of manual interventions.

Genetic variants associated with the root system architecture of oilseed rape (Brassica napus L.) under contrasting phosphate supply.

Breeding crops with ideal root system architecture for efficient absorption of phosphorus is an important strategy to reduce the use of phosphate fertilizers. To investigate genetic variants leading to changes in root system architecture, 405 oilseed rape cultivars were genotyped with a 60K Brassica Infinium SNP array in low and high P environments. A total of 285 single-nucleotide polymorphisms were associated with root system architecture traits at varying phosphorus levels. Nine single-nucleotide polymorphisms corroborate a previous linkage analysis of root system architecture quantitative trait loci in the BnaTNDH population. One peak single-nucleotide polymorphism region on A3 was associated with all root system architecture traits and co-localized with a quantitative trait locus for primary root length at low phosphorus. Two more single-nucleotide polymorphism peaks on A5 for root dry weight at low phosphorus were detected in both growth systems and co-localized with a quantitative trait locus for the same trait. The candidate genes identified on A3 form a haplotype 'BnA3Hap', that will be important for understanding the phosphorus/root system interaction and for the incorporation into Brassica napus breeding programs.

QTL meta-analysis of root traits in Brassica napus under contrasting phosphorus supply in two growth systems.

A high-density SNP-based genetic linkage map was constructed and integrated with a previous map in the Tapidor x Ningyou7 (TNDH) Brassica napus population, giving a new map with a total of 2041 molecular markers and an average marker density which increased from 0.39 to 0.97 (0.82 SNP bin) per cM. Root and shoot traits were screened under low and 'normal' phosphate (Pi) supply using a 'pouch and wick' system, and had been screened previously in an agar based system. The P-efficient parent Ningyou7 had a shorter primary root length (PRL), greater lateral root density (LRD) and a greater shoot biomass than the P-inefficient parent Tapidor under both treatments and growth systems. Quantitative trait loci (QTL) analysis identified a total of 131 QTL, and QTL meta-analysis found four integrated QTL across the growth systems. Integration reduced the confidence interval by ~41%. QTL for root and shoot biomass were co-located on chromosome A3 and for lateral root emergence were co-located on chromosomes A4/C4 and C8/C9. There was a major QTL for LRD on chromosome C9 explaining ~18% of the phenotypic variation. QTL underlying an increased LRD may be a useful breeding target for P uptake efficiency in Brassica.

IR study of cross-strand coupling in a beta-hairpin peptide using isotopic labels.

Model beta-hairpin peptides can be used to develop understanding of fundamental elements of beta-sheet secondary structure formation and stability. We have studied two 13C-labeled variants of a beta-hairpin peptide modified from a design originally proposed by Gellman: Arg-Tyr-Val-Glu-Val-Aib-Gly-Lys-Lys-Ile-Leu-Gln. (In this peptide, the two italicized residues form a beta-turn, while 13C-labels are on the amide C=O of Val3, Lys8 in HBG-L and Val3, Ile10 in HBG-S.) Both these peptides are labeled on opposite strands of the hairpin, but differ in the labeling pattern. One (HBG-L) forms a large (14-atom) H-bonded ring of labeled C=Os, while the other (HBG-S) forms a small (10-atom) H-bonded ring. These impact the amide I infrared spectra, with HBG-L having a 13C frequency and intensity higher than that of HBG-S, in good agreement with our spectral simulations based on quantum mechanically derived force fields. The thermal behavior of both peptides yields a broad thermal transition and lacks an isosbestic point. The 13C band for HBG-L has the largest intensity change with temperature, distinct from the 12C change and the HBG-S 13C change.

Eating attitudes in English secondary school students: influences of ethnicity, gender, mood, and social class.

OBJECTIVE: To examine the effects of ethnicity, gender, socioeconomic position, self-esteem, and emotion on eating attitudes in adolescents. METHOD: Questionnaire survey of 722 students in two English schools, using Eating Attitude Test-26 (EAT), Rosenberg Self-Esteem Scale, and Angold vMood and Feeling instruments. RESULTS: EAT scores were significantly higher for Asians and Muslims and for mixed-race subjects than for White or African Caribbean subjects (p =.003). Adjusted odds ratios for having a very high EAT score (>20) were 2.4 (95% confidence interval [CI] 1.0-6.0) in Asians and Muslims and 2.9 (95% CI 1.3-18.6) in mixed-race subjects, compared with White subjects. Having only one parent employed was also independently associated with a very high EAT score, compared with having both parents employed. Similar associations were found for a moderately high EAT score (>10) and for a combination of low self-esteem and high EAT score. Low self-esteem and depressed mood were independently associated with a high EAT score. DISCUSSION: Ethnicity, socioeconomic position, self-esteem, and depression, but not gender, were independently associated with eating attitudes. Effects of cultural and socioeconomic stresses on eating disorders may be mediated through depressed mood and low self-esteem.