Comparative mapping of quantitative trait loci involved in heterosis for seedling and yield traits in oilseed rape (Brassica napus L.)

Little is known about the genetic control of heterosis in the complex polyploid crop species oilseed rape (Brassica napus L.). In this study, two large doubled-haploid (DH) mapping populations and two corresponding sets of backcrossed test hybrids (THs) were analysed in controlled greenhouse experiments and extensive field trials for seedling biomass and yield performance traits, respectively. Genetic maps from the two populations, aligned with the help of common simple sequence repeat markers, were used to localise and compare quantitative trait loci (QTL) related to the expression of heterosis for seedling developmental traits, plant height at flowering, thousand seed mass, seeds per silique, siliques per unit area and seed yield. QTL were mapped using data from the respective DH populations, their corresponding TH populations and from mid-parent heterosis (MPH) data, allowing additive and dominance effects along with digenic epistatic interactions to be estimated. A number of genome regions containing numerous heterosis-related QTL involved in different traits and at different developmental stages were identified at corresponding map positions in the two populations. The co-localisation of per se QTL from the DH population datasets with heterosis-related QTL from the MPH data could indicate regulatory loci that may also contribute to fixed heterosis in the highly duplicated B. napus genome. Given the key role of epistatic interactions in the expression of heterosis in oilseed rape, these QTL hotspots might harbour genes involved in regulation of heterosis (including fixed heterosis) for different traits throughout the plant life cycle, including a significant overall influence on heterosis for seed yield

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Magnetic Circular Dichroism Spectroscopy of Metalloproteins

Metals and metal clusters in proteins typically serve as important structural/functional motifs. Because of this reason, there is a wide range of techniques that specifically probe the structure and energy levels of metals in metalloproteins. One technique, magnetic circular dichroism (MCD) spectroscopy, is the focus of this chapter. MCD spectroscopy monitors the circular dichroism spectrum induced by a magnetic field and is an effective way of obtaining electronic and structural information of paramagnetic metal ions or clusters. The basic methodology of this technique is discussed along with examples of how MCD spectroscopy can be used to elucidate typical metal clusters in proteins. Special emphasis is placed on iron-sulfur (FeS) clusters

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