The Genetic Basis of Composite Spike Form in Barley and 'Miracle-Wheat'

Inflorescences of the tribe Triticeae, which includes wheat (Triticum sp. L.) and barley (Hordeum vulgare L.) are characterized by sessile spikelets directly borne on the main axis, thus forming a branchless spike. 'Compositum-Barley' and tetraploid 'Miracle-Wheat' (T. turgidum convar. compositum (L.f.) Filat.) display noncanonical spike-branching in which spikelets are replaced by lateral branch-like structures resembling small-sized secondary spikes. As a result of this branch formation 'Miracle-Wheat' produces significantly more grains per spike, leading to higher spike yield. In this study, we first isolated the gene underlying spike-branching in 'Compositum-Barley,' i.e., compositum 2 (com2). Moreover, we found that COM2 is orthologous to the branched head(t) (bh(t)) locus regulating spike branching in tetraploid 'Miracle-Wheat.' Both genes possess orthologs with similar functions in maize BRANCHED SILKLESS 1 (BD1) and rice FRIZZY PANICLE/BRANCHED FLORETLESS 1 (FZP/BFL1) encoding AP2/ERF transcription factors. Sequence analysis of the bh(t) locus in a collection of mutant and wild-type tetraploid wheat accessions revealed that a single amino acid substitution in the DNA-binding domain gave rise to the domestication of 'Miracle-Wheat.' mRNA in situ hybridization, microarray experiments, and independent qRT-PCR validation analyses revealed that the branch repression pathway in barley is governed through the spike architecture gene Six-rowed spike 4 regulating COM2 expression, while HvIDS1 (barley ortholog of maize INDETERMINATE SPIKELET 1) is a putative downstream target of COM2. These findings presented here provide new insights into the genetic basis of spike architecture in Triticeae, and have disclosed new targets for genetic manipulations aiming at boosting wheat's yield potential.

Selection of candidate genes for grape proanthocyanidin pathway by an integrative approach

Proanthocyanidins (PA) play a major role in plant protection against biotic and abiotic stresses. Moreover these molecules are known to be beneficial for human health and are responsible for astringency of foods and beverages such as wine and thus have a great impact on the final quality of the product. Genes playing a role in the PA pathway are only partially known. The amount of available transcriptomic and genetic data to select candidate genes without a priori knowledge from orthologous function increases every day. However, the methods used so far generate so many candidate genes that it is impossible to validate all of them. In this study, we used an integrative strategy based on different screening methods to select a reduced list of candidate genes. We have crossed results from different screening methods including QTL mapping and three transcriptomic studies to select 20 candidate genes, located in QTL intervals and fulfilling at least two transcriptomic screenings. This list includes three glucosyltransferases, already suspected to have a role in the PA biosynthetic pathway. Among the 17 remaining genes, we selected three genes to perform further analysis by association genetic studies. For each of these genes, we found a polymorphism linked to PA variation. The three genes (VvMybC2-L1, VvGAT-like and VvCob-like), not previously known to play a role in PA synthesis, are promising candidates for further molecular physiology studies.

Mixed model association scans of multi-environmental trial data reveal major loci controlling yield and yield related traits in Hordeum vulgare in Mediterranean environments

An association panel consisting of 185 accessions representative of the barley germplasm cultivated in the Mediterranean basin was used to localise quantitative trait loci (QTL) controlling grain yield and yield related traits. The germplasm set was genotyped with 1,536 SNP markers and tested for associations with phenotypic data gathered over 2 years for a total of 24 year × location combinations under a broad range of environmental conditions. Analysis of multi-environmental trial (MET) data by fitting a mixed model with kinship estimates detected from two to seven QTL for the major components of yield including 1000 kernel weight, grains per spike and spikes per m(2), as well as heading date, harvest index and plant height. Several of the associations involved SNPs tightly linked to known major genes determining spike morphology in barley (vrs1 and int-c). Similarly, the largest QTL for heading date co-locates with SNPs linked with eam6, a major locus for heading date in barley for autumn sown conditions. Co-localization of several QTL related to yield components traits suggest that major developmental loci may be linked to most of the associations. This study highlights the potential of association genetics to identify genetic variants controlling complex traits.

Genetic dissection of barley morphology and development

Since the early 20th century, barley (Hordeum vulgare) has been a model for investigating the effects of physical and chemical mutagens and for exploring the potential of mutation breeding in crop improvement. As a consequence, extensive and well-characterized collections of morphological and developmental mutants have been assembled that represent a valuable resource for exploring a wide range of complex and fundamental biological processes. We constructed a collection of 881 backcrossed lines containing mutant alleles that induce a majority of the morphological and developmental variation described in this species. After genotyping these lines with up to 3,072 single nucleotide polymorphisms, comparison to their recurrent parent defined the genetic location of 426 mutant alleles to chromosomal segments, each representing on average <3% of the barley genetic map. We show how the gene content in these segments can be predicted through conservation of synteny with model cereal genomes, providing a route to rapid gene identification.

Making the most of 'omics' for crop breeding

Adoption of new breeding technologies is likely to underpin future gains in crop productivity. The rapid advances in 'omics' technologies provide an opportunity to generate new datasets for crop species. Integration of genome and functional omics data with genetic and phenotypic information is leading to the identification of genes and pathways responsible for important agronomic phenotypes. In addition, high-throughput genotyping technologies enable the screening of large germplasm collections to identify novel alleles from diverse sources, thus offering a major expansion in the variation available for breeding. In this review, we discuss these advances, which have opened the door to new techniques for construction and screening of breeding populations, to increase ultimately the efficiency of selection and accelerate the rates of genetic gain.

Recent achievements and trends in experimental plant biology

Between 21 and 25 September 2009, Krakow hosted the 4th Conference of the Polish Society of Experimental Plant Biology, co-organized with the Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, and supported by the Biochemical Society. The aim of the conference was to present and discuss the most important topics in different disciplines of plant experimental science as well as to facilitate the interaction and co-operation between scientists. To achieve this goal, about 30 top specialists in various areas of plant biology were invited to give plenary lectures in the following sessions: Plant structure and development; Plant-microbial interactions; Mitochondria and chloroplasts in cell metabolism; Stress tolerance in plants; Structural and functional organization of plant genomes; Mutants in developmental and metabolic studies; Secondary metabolites as pharmaceutics and nutraceutics; Plant membranes; and Integrating plant functions via signalling molecules: molecular mechanisms. Some of the main problems highlighted in the plenary lectures are briefly summarized in the present paper. Two poster sessions enabled a discussion of over 200 posters presented. The conference had an international character, its official language was English, and among the more than 350 participants, about 60 were from abroad. Several plenary lectures were prepared as short review papers and they are published in this issue of Biochemical Society Transactions.