About 12,000 years ago in the Near East, humans began the transition from hunter-gathering to agriculture-based societies. Barley was a founder crop in this process, and the most important steps in its domestication were mutations in two adjacent, dominant, and complementary genes, through which grains were retained on the inflorescence at maturity, enabling effective harvesting. Independent recessive mutations in each of these genes caused cell wall thickening in a highly specific grain "disarticulation zone," converting the brittle floral axis (the rachis) of the wild-type into a tough, non-brittle form that promoted grain retention. By tracing the evolutionary history of allelic variation in both genes, we conclude that spatially and temporally independent selections of germplasm with a non-brittle rachis were made during the domestication of barley by farmers in the southern and northern regions of the Levant, actions that made a major contribution to the emergence of early agrarian societies.

Dps, the nonspecific DNA-binding protein from starved cells, is the most abundant protein in stationaryphase Escherichia coli. Dps homologs are found throughout the bacteria and in at least one archaeal species. Dps has been shown to protect cells from oxidative stress during exponential-phase growth. During stationary phase, Dps organizes the chromosome into a highly ordered, stable nucleoprotein complex called the biocrystal. We show here that Dps is required for long-term stationary-phase viability under competitive conditions and that dps mutants have altered lag phases compared to wild-type cells. We also show that during stationary phase Dps protects the cell not only from oxidative stress but also from UV and gamma irradiation, iron and copper toxicity, thermal stress, and acid and base shock. The protective roles of Dps are most likely achieved through a combination of functions associated with the protein-DNA binding and chromosome compaction, metal chelation, ferroxidase activity, and regulation of gene expression.Dps, the DNA-binding protein from starved cells, is among the most abundant proteins in stationary-phase Escherichia coli. As cells transition from exponential-phase growth to stationary phase, Dps is induced in an RpoS-dependent manner, reaching up to 200,000 molecules per cell (2). Dps is also regulated by OxyR and 70 in response to oxidative stress during exponential phase (3). The protein has nonspecific DNA-binding activity, affects the expression of at least three dozen genes, and plays a role in various stress responses, including protection from oxidative damage (2, 18). The protein's active form is a hollow, spherical, dodecamer with an outer diameter of ϳ90 Å and an interior core diameter of ϳ45 Å (2, 27). During stationary phase, Dps binds the chromosome, forming a highly ordered and stable nucleoprotein complex called a biocrystal. This biocrystalline form is distinct from the exponential-phase configuration of the nucleoid and is unique to stationary-phase cells (12,19,27). Biocrystal formation contributes to the ability of Dps to affect gene expression and protects chromosomal DNA. Dps shows significant structural homology to the ferritins, a highly conserved family of proteins found in virtually all organisms, and possesses ferroxidase activity and the ability to sequester iron (15). This iron-binding activity very likely plays a significant role in the ability of Dps to protect the chromosome from oxidative damage.For E. coli, most studies of Dps have focused on its role in oxidative damage protection, particularly against peroxides, during exponential phase (2, 18). Here we expand the repertoire of potential stressors to include long-term stationaryphase incubation under conditions of nutrient stress and competition, the presence of oxidizing agents and heavy metals, thermal stress, ionizing and UV radiation, and extremes of pH. Our working hypothesis is that this multifunctional protein is involved in many cellular processes and probably functions via several different mecha...

The cleistogamous flower sheds its pollen before opening, forcing plants with this habit to be almost entirely autogamous. Cleistogamy also provides a means of escape from cereal head blight infection and minimizes pollen-mediated gene flow. The lodicule in cleistogamous barley is atrophied. We have isolated cleistogamy 1 (Cly1) by positional cloning and show that it encodes a transcription factor containing two AP2 domains and a putative microRNA miR172 targeting site, which is an ortholog of Arabidopsis thaliana AP2. The expression of Cly1 was concentrated within the lodicule primordia. We established a perfect association between a synonymous nucleotide substitution at the miR172 targeting site and cleistogamy. Cleavage of mRNA directed by miR172 was detectable only in a noncleistogamous background. We conclude that the miR172-derived down-regulation of Cly1 promotes the development of the lodicules, thereby ensuring noncleistogamy, although the single nucleotide change at the miR172 targeting site results in the failure of the lodicules to develop properly, producing the cleistogamous phenotype.closed flowering | miR172 | AP2 | cly1 | lodicule

Key messageGenome-wide association study (GWAS) on 923 maize lines and validation in bi-parental populations identified significant genomic regions for kernel-Zinc and-Iron in maize.AbstractBio-fortification of maize with elevated Zinc (Zn) and Iron (Fe) holds considerable promise for alleviating under-nutrition among the world’s poor. Bio-fortification through molecular breeding could be an economical strategy for developing nutritious maize, and hence in this study, we adopted GWAS to identify markers associated with high kernel-Zn and Fe in maize and subsequently validated marker-trait associations in independent bi-parental populations. For GWAS, we evaluated a diverse maize association mapping panel of 923 inbred lines across three environments and detected trait associations using high-density Single nucleotide polymorphism (SNPs) obtained through genotyping-by-sequencing. Phenotyping trials of the GWAS panel showed high heritability and moderate correlation between kernel-Zn and Fe concentrations. GWAS revealed a total of 46 SNPs (Zn-20 and Fe-26) significantly associated (P ≤ 5.03 × 10−05) with kernel-Zn and Fe concentrations with some of these associated SNPs located within previously reported QTL intervals for these traits. Three double-haploid (DH) populations were developed using lines identified from the panel that were contrasting for these micronutrients. The DH populations were phenotyped at two environments and were used for validating significant SNPs (P ≤ 1 × 10−03) based on single marker QTL analysis. Based on this analysis, 11 (Zn) and 11 (Fe) SNPs were found to have significant effect on the trait variance (P ≤ 0.01, R2 ≥ 0.05) in at least one bi-parental population. These findings are being pursued in the kernel-Zn and Fe breeding program, and could hold great value in functional analysis and possible cloning of high-value genes for these traits in maize.Electronic supplementary materialThe online version of this article (10.1007/s00122-018-3089-3) contains supplementary material, which is available to authorized users.

Maize is a major source of food security and economic development in sub-Saharan Africa (SSA), Latin America, and the Caribbean, and is among the top three cereal crops in Asia. Yet, maize is deficient in certain essential amino acids, vitamins, and minerals. Biofortified maize cultivars enriched with essential minerals and vitamins could be particularly impactful in rural areas with limited access to diversified diet, dietary supplements, and fortified foods. Significant progress has been made in developing, testing, and deploying maize cultivars biofortified with quality protein maize (QPM), provitamin A, and kernel zinc. In this review, we outline the status and prospects of developing nutritionally enriched maize by successfully harnessing conventional and molecular marker-assisted breeding, highlighting the need for intensification of efforts to create greater impacts on malnutrition in maize-consuming populations, especially in the low-and middle-income countries. Molecular marker-assisted selection methods are particularly useful for improving nutritional traits since conventional breeding methods are relatively constrained by the cost and throughput of nutritional trait phenotyping.