Abstract
Iron bioavailability varies dramatically between soil types across the globe. This has given rise to high levels of natural variation in plant iron responses, allowing members of even a ...single species to thrive across a wide range of soil types. In recent years we have seen the use of genome-wide association analysis to identify natural variants underlying plant responses to changes in iron availability in both Arabidopsis and important crop species. These studies have provided insights into which genes have been important in shaping local adaptation to iron availability in different plant species and have allowed the discovery of novel regulators and mechanisms, not previously identified using mutagenesis approaches. Furthermore, these studies have allowed the identification of markers that can be used to accelerate breeding of future elite varieties with increased resilience to iron stress and improved nutritional quality. The studies highlighted here show that, in addition to studying plant responses to iron alone, it is important to consider these responses within the context of plant nutrition more broadly and to also consider iron regulation in relation to additional traits of agronomic importance such as yield and disease resistance.
Exploring natural variation is a powerful approach to understanding plant responses to iron availability and has allowed the discovery of novel genetic regulators and mechanisms that have shaped plant adaptation.
Background and aims
Tobacco and nicotine marketplaces have diversified over the past decade, including with the introduction of heated tobacco products (HTPs), such as the brand IQOS. HTPs typically ...heat tobacco to generate an aerosol that is inhaled. HTP nomenclature is lacking, and how HTP users define and identify themselves remains understudied. Research in this area is important because language can construct identity, and identity can shape behaviour. This study aimed to explore users' language choice when describing IQOS use, and how language relates to user identity.
Methods
Qualitative interviews in London, United Kingdom, with 30 adult current and former IQOS users. Analyses were guided by Iterative Categorization.
Results
Overall, participants expressed confusion and a lack of suitable terminology for how to describe IQOS use. Verbs such as heating and IQOSing were rarely endorsed. Most often, participants reverted to smoking when describing IQOS use and commonly referred to HEETS (tobacco sticks) as cigarettes. Yet the lack of combustion, electronic device, cleaner experience and perceived reductions in health risks led some to frame IQOS as distinct from smoking. Vaping was generally considered inappropriate for describing IQOS use. Participants also manipulated language to suit their circumstances and manage their identity, whereas some IQOS users embraced the terms smoking and smoker, most were eager to distinguish between using IQOS and being labelled a smoker because of the associated negative connotations and to align with perceptions of IQOS use as a better, less harmful behaviour. Instead, when describing their identity, IQOS users more willingly identified as vapers, or ex‐smokers, or created new identities (e.g. HEET user).
Conclusions
People who use or have used IQOS (a brand of heated tobacco product) are ambiguous about IQOS terminology. Participants in this study commonly referred to IQOS use as smoking for lack of a more suitable term, but also resisted being labelled as smokers, a choice that may influence smoking cessation. Clear terminology must be used in surveys and by healthcare professionals when asking about cigarette smoking and e‐cigarette and heated tobacco product use.
The current approach to reducing the tendency for wheat grown under high fertilizer conditions to collapse (lodge) under the weight of its grain is based on reducing stem height via the introduction ...of Rht genes. However, these reduce the yield of straw (itself an important commodity) and introduce other undesirable characteristics. Identification of alternative height-control loci is therefore of key interest. In addition, the improvement of stem mechanical strength provides a further way through which lodging can be reduced.
To investigate the prospects for genetic alternatives to Rht, we assessed variation for plant height and stem strength properties in a training genetic diversity panel of 100 wheat accessions fixed for Rht. Using mRNAseq data derived from RNA purified from leaves, functional genotypes were developed for the panel comprising 42,066 Single Nucleotide Polymorphism (SNP) markers and 94,060 Gene Expression Markers (GEMs). In the first application in wheat of the recently-developed method of Associative Transcriptomics, we identified associations between trait variation and both SNPs and GEMs. Analysis of marker-trait associations revealed candidates for the causative genes underlying the trait variation, implicating xylan acetylation and the COP9 signalosome as contributing to stem strength and auxin in the control of the observed variation for plant height. Predictive capabilities of key markers for stem strength were validated using a test genetic diversity panel of 30 further wheat accessions.
This work illustrates the power of Associative Transcriptomics for the exploration of complex traits of high agronomic importance in wheat. The careful selection of genotypes included in the analysis, allowed for high resolution mapping of novel trait-controlling loci in this staple crop. The use of Gene Expression markers coupled with the more traditional sequence-based markers, provides the power required to understand the biological context of the marker-trait associations observed. This not only adds to the wealth of knowledge that we strive to accumulate regarding gene function and plant adaptation, but also provides breeders with the information required to make more informed decisions regarding the potential consequences of incorporating the use of particular markers into future breeding programmes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Core Ideas
Efficiency in genomic selection is not particularly based on detailed genotype profiling facilitated by maximum marker density.
Extensive genome‐wide linkage disequilibrium is a common ...characteristic of breeding pools in many crop species.
Every quantitative trait locus across the genome can be captured by one or a few representative markers.
Fewer representative markers selected in respect of linkage disequilibrium (LD) can capture the association between a genomic region and a phenotypic trait.
Low‐density marker sets enable genomic prediction accuracies in breeding populations with strong LD comparable to those achieved with high‐density genotyping.
Genomic selection (GS) has revolutionized breeding for quantitative traits in plants, offering potential to optimize resource allocation in breeding programs and increase genetic gain per unit of time. Modern high‐density single nucleotide polymorphism (SNP) arrays comprising up to several hundred thousand markers provide a user‐friendly technology to characterize the genetic constitution of whole populations and for implementing GS in breeding programs. However, GS does not build upon detailed genotype profiling facilitated by maximum marker density. With extensive genome‐wide linkage disequilibrium (LD) being a common characteristic of breeding pools, fewer representative markers from available high‐density genotyping platforms could be sufficient to capture the association between a genomic region and a phenotypic trait. To examine the effects of reduced marker density on genomic prediction accuracy, we collected data on three traits across 2 yr in a panel of 203 homozygous Chinese semiwinter rapeseed (Brassica napus L.) inbred lines, broadly encompassing allelic variability in the Asian B. napus genepool. We investigated two approaches to selecting subsets of markers: a trait‐dependent strategy based on genome‐wide association study (GWAS) significance thresholds and a trait‐independent method to detect representative tag SNPs. Prediction accuracies were evaluated using cross‐validation with ridge‐regression best linear unbiased predictions (rrBLUP). With semiwinter rapeseed as a model species, we demonstrate that low‐density marker sets comprising a few hundred to a few thousand markers enable high prediction accuracies in breeding populations with strong LD comparable to those achieved with high‐density arrays. Our results are valuable for facilitating routine application of cost‐efficient GS in breeding programs.
The same species of plant can exhibit very diverse sizes and shapes of organs that are genetically determined. Characterising genetic variation underlying this morphological diversity is an important ...objective in evolutionary studies and it also helps identify the functions of genes influencing plant growth and development. Extensive screens of mutagenised Arabidopsis populations have identified multiple genes and mechanisms affecting organ size and shape, but relatively few studies have exploited the rich diversity of natural populations to identify genes involved in growth control.
We screened a relatively well characterised collection of Arabidopsis thaliana accessions for variation in petal size. Association analyses identified sequence and gene expression variation on chromosome 4 that made a substantial contribution to differences in petal area. Variation in the expression of a previously uncharacterised gene At4g16850 (named as KSK) had a substantial role on variation in organ size by influencing cell size. Over-expression of KSK led to larger petals with larger cells and promoted the formation of stamenoid features. The expression of auxin-responsive genes known to limit cell growth was reduced in response to KSK over-expression. ANT expression was also reduced in KSK over-expression lines, consistent with altered floral identities. Auxin responses were reduced in KSK over-expressing cells, consistent with changes in auxin-responsive gene expression. KSK may therefore influence auxin responses during petal development.
Understanding how genetic variation influences plant growth is important for both evolutionary and mechanistic studies. We used natural populations of Arabidopsis thaliana to identify sequence variation in a promoter region of Arabidopsis accessions that mediated differences in the expression of a previously uncharacterised membrane protein. This variation contributed to altered auxin responses and cell size during petal growth.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Lodging continues to be a major cause of yield loss in important crop species such as
Brassica napus.
Understanding the genetic regulation of lodging resistance is therefore of key interest to ...breeders worldwide. Current strategies aimed at minimising lodging risk involve the incorporation of dwarfing genes or the application of plant growth regulators. However, despite these efforts, lodging continues to be a persistent problem and it is therefore of high interest that novel, complimentary strategies for lodging control are implemented. One approach would be to focus on understanding the genetic properties underlying stem mechanical strength. With this in mind, we screened a training genetic diversity panel of
B
.
napus
accession for variation in stem mechanical strength and related traits. Using Associative Transcriptomics, we identified molecular markers for a suite of valuable traits. Using an independent test genetic diversity panel, we show that the methods employed are robust for identification of predictive markers. Furthermore, based on conserved synteny with
Arabidopsis thaliana
, we are able to provide a biological context to the marker associations detected and provide evidence for a role in pectin methylesterification in contributing to stem mechanical strength in
Brassicaceae.
Wheat straw is an attractive substrate for second generation ethanol production because it will complement and augment wheat production rather than competing with food production. However, like other ...sources of lignocellulosic biomass, even from a single species, it is heterogeneous in nature due to the different tissues and cell types, and this has implications for saccharification efficiency. The aim of this study has been to use Fourier transform infrared (FTIR) spectroscopy and Partial least squares (PLS) modelling to rapidly screen wheat cultivars for the levels of component tissues, the carbohydrate composition and lignin content, and the levels of simple cross-linking phenolics such as ferulic and diferulic acids.
FTIR spectroscopy and PLS modelling was used to analyze the tissue and chemical composition of wheat straw biomass. Predictive models were developed to evaluate the variability in the concentrations of the cell wall sugars, cell wall phenolics and acid-insoluble lignin. Models for the main sugars, phenolics and lignin were validated and then used to evaluate the variation in total biomass composition across 90 cultivars of wheat grown over two seasons.
Whilst carbohydrate and lignin components varied across the varieties, this mainly reflected differences in the ratios of the component tissues rather than differences in the composition of those tissues. Further analysis indicated that on a mol% basis, relative levels of sugars within the tissues varied to only a small degree. There were no clear associations between simple phenolics and tissues. The results provide a basis for improving biomass quality for biofuels production through selection of cultivars with appropriate tissue ratios.
PDF
