De novo transcriptome assemblies of C and C non-model grass species reveal key differences in leaf development.

Background: C photosynthesis is a mechanism that plants have evolved to reduce the rate of photorespiration during the carbon fixation process. The C pathway allows plants to adapt to high temperatures and light while more efficiently using resources, such as water and nitrogen. Despite decades of studies, the evolution of the C pathway from a C ancestor remains a biological enigma.

Demonstration of local adaptation in maize landraces by reciprocal transplantation.

Populations are locally adapted when they exhibit higher fitness than foreign populations in their native habitat. Maize landrace adaptations to highland and lowland conditions are of interest to researchers and breeders. To determine the prevalence and strength of local adaptation in maize landraces, we performed a reciprocal transplant experiment across an elevational gradient in Mexico.

Meeting in the Middle: Lessons and Opportunities from Studying C-C Intermediates.

The discovery of C-C intermediate species nearly 50 years ago opened up a new avenue for studying the evolution of photosynthetic pathways. Intermediate species exhibit anatomical, biochemical, and physiological traits that range from C to C. A key feature of C-C intermediates that utilize C photosynthesis is the improvement in photosynthetic efficiency compared with C species.

The genetic architecture of leaf stable carbon isotope composition in Zea mays and the effect of transpiration efficiency on leaf elemental accumulation.

With increased demand on freshwater resources for agriculture, it is imperative that more water-use efficient crops are developed. Leaf stable carbon isotope composition, δ13C, is a proxy for transpiration efficiency and a possible tool for breeders, but the underlying mechanisms effecting δ13C in C4 plants are not known. It has been suggested that differences in specific leaf area (SLA), which potentially reflects variation in internal CO2 diffusion, can impact leaf δ13C.

Genomic Prediction of Yield Traits in Single-Cross Hybrid Rice ( L.).

Hybrid rice varieties can outyield the best inbred varieties by 15 - 30% with appropriate management. However, hybrid rice requires more inputs and management than inbred rice to realize a yield advantage in high-yielding environments. The development of stress-tolerant hybrid rice with lowered input requirements could increase hybrid rice yield relative to production costs.

Heterosis and Hybrid Crop Breeding: A Multidisciplinary Review.

Although hybrid crop varieties are among the most popular agricultural innovations, the rationale for hybrid crop breeding is sometimes misunderstood. Hybrid breeding is slower and more resource-intensive than inbred breeding, but it allows systematic improvement of a population by recurrent selection and exploitation of heterosis simultaneously. Inbred parental lines can identically reproduce both themselves and their F progeny indefinitely, whereas outbred lines cannot, so uniform outbred lines must be bred indirectly through their inbred parents to harness heterosis.

Leaf Angle eXtractor: A high-throughput image processing framework for leaf angle measurements in maize and sorghum.

Premise: Maize yields have significantly increased over the past half-century owing to advances in breeding and agronomic practices. Plants have been grown in increasingly higher densities due to changes in plant architecture resulting in plants with more upright leaves, which allows more efficient light interception for photosynthesis. Natural variation for leaf angle has been identified in maize and sorghum using multiple mapping populations.

Insights from transcriptome profiling on the non-photosynthetic and stomatal signaling response of maize carbonic anhydrase mutants to low CO.

Background: Carbonic anhydrase (CA) catalyzes the hydration of CO in the first biochemical step of C photosynthesis, and has been considered a potentially rate-limiting step when CO availability within a leaf is low. Previous work in Zea mays (maize) with a double knockout of the two highest-expressed β-CA genes, CA1 and CA2, reduced total leaf CA activity to less than 3% of wild-type. Surprisingly, this did not limit photosynthesis in maize at ambient or higher COconcentrations.

Leaf stable carbon isotope composition reflects transpiration efficiency in Zea mays.

The increasing demand for food production and predicted climate change scenarios highlight the need for improvements in crop sustainability. The efficient use of water will become increasingly important for rain-fed agricultural crops even in fertile regions that have historically received ample precipitation. Improvements in water-use efficiency in Zea mays have been limited, and warrant a renewed effort aided by molecular breeding approaches.

Carbonic Anhydrase Mutants in Have Altered Stomatal Responses to Environmental Signals.

Stomata regulate transpirational water loss and CO uptake for photosynthesis in response to changing environmental conditions. Research investigating stomatal movement has mostly been conducted in C eudicot species, which have very different CO requirements for photosynthesis relative to C grasses. Carbonic anhydrase (CA) catalyzes the hydration of CO, and its activity has been linked to stomatal aperture regulation in eudicots.

Biochemical and transcriptomic analysis of maize diversity to elucidate drivers of leaf carbon isotope composition.

Carbon isotope discrimination is used to study CO2 diffusion, substrate availability for photosynthesis, and leaf biochemistry, but the intraspecific drivers of leaf carbon isotope composition (δ13C) in C4 species are not well understood. In this study, the role of photosynthetic enzymes and post-photosynthetic fractionation on δ13C (‰) was explored across diverse maize inbred lines. A significant 1.

Selection During Maize Domestication Targeted a Gene Network Controlling Plant and Inflorescence Architecture.

Selection during evolution, whether natural or artificial, acts through the phenotype. For multifaceted phenotypes such as plant and inflorescence architecture, the underlying genetic architecture is comprised of a complex network of interacting genes rather than single genes that act independently to determine the trait. As such, selection acts on entire gene networks.

The draft genome of the C panicoid grass species Dichanthelium oligosanthes.

Background: Comparisons between C and C grasses often utilize C species from the subfamilies Ehrhartoideae or Pooideae and C species from the subfamily Panicoideae, two clades that diverged over 50 million years ago. The divergence of the C panicoid grass Dichanthelium oligosanthes from the independent C lineages represented by Setaria viridis and Sorghum bicolor occurred approximately 15 million years ago, which is significantly more recent than members of the Bambusoideae, Ehrhartoideae, and Pooideae subfamilies. D.

A Gene for Genetic Background in Zea mays: Fine-Mapping enhancer of teosinte branched1.2 to a YABBY Class Transcription Factor.

The effects of an allelic substitution at a gene often depend critically on genetic background, i.e., the genotypes at other genes in the genome.

Cross species selection scans identify components of C4 photosynthesis in the grasses.

C photosynthesis is perhaps one of the best examples of convergent adaptive evolution with over 25 independent origins in the grasses (Poaceae) alone. The availability of high quality grass genome sequences presents new opportunities to explore the mechanisms underlying this complex trait using evolutionary biology-based approaches. In this study, we performed genome-wide cross-species selection scans in C lineages to facilitate discovery of C genes.

Evidence That the Origin of Naked Kernels During Maize Domestication Was Caused by a Single Amino Acid Substitution in tga1.

teosinte glume architecture1 (tga1), a member of the SBP-box gene family of transcriptional regulators, has been identified as the gene conferring naked kernels in maize vs. encased kernels in its wild progenitor, teosinte. However, the identity of the causative polymorphism within tga1 that produces these different phenotypes has remained unknown.

Comparative analyses of C₄ and C₃ photosynthesis in developing leaves of maize and rice.

C₄ and C₃ photosynthesis differ in the efficiency with which they consume water and nitrogen. Engineering traits of the more efficient C₄ photosynthesis into C₃ crops could substantially increase crop yields in hot, arid conditions. To identify differences between C₄ and C₃ photosynthetic mechanisms, we profiled metabolites and gene expression in the developing leaves of Zea mays (maize), a C₄ plant, and Oryza sativa (rice), a C₃ plant, using a statistical method named the unified developmental model (UDM).

A Limited Role for Carbonic Anhydrase in C4 Photosynthesis as Revealed by a ca1ca2 Double Mutant in Maize.

Carbonic anhydrase (CA) catalyzes the first biochemical step of the carbon-concentrating mechanism of C plants, and in C monocots it has been suggested that CA activity is near limiting for photosynthesis. Here, we test this hypothesis through the characterization of transposon-induced mutant alleles of Ca1 and Ca2 in maize (Zea mays). These two isoforms account for more than 85% of the CA transcript pool.

Evidence for a natural allelic series at the maize domestication locus teosinte branched1.

Despite numerous quantitative trait loci and association mapping studies, our understanding of the extent to which natural allelic series contribute to the variation for complex traits is limited. In this study, we investigate the occurrence of a natural allelic series for complex traits at the teosinte branched1 (tb1) gene in natural populations of teosinte (Zea mays ssp. parviglumis, Z.

Identification of a functional transposon insertion in the maize domestication gene tb1.

Genetic diversity created by transposable elements is an important source of functional variation upon which selection acts during evolution. Transposable elements are associated with adaptation to temperate climates in Drosophila, a SINE element is associated with the domestication of small dog breeds from the gray wolf and there is evidence that transposable elements were targets of selection during human evolution. Although the list of examples of transposable elements associated with host gene function continues to grow, proof that transposable elements are causative and not just correlated with functional variation is limited.

Do large effect QTL fractionate? A case study at the maize domestication QTL teosinte branched1.

Quantitative trait loci (QTL) mapping is a valuable tool for studying the genetic architecture of trait variation. Despite the large number of QTL studies reported in the literature, the identified QTL are rarely mapped to the underlying genes and it is usually unclear whether a QTL corresponds to one or multiple linked genes. Similarly, when QTL for several traits colocalize, it is usually unclear whether this is due to the pleiotropic action of a single gene or multiple linked genes, each affecting one trait.