Association mapping is a powerful approach for dissecting the genetic architecture of complex quantitative traits using high-density SNP markers in maize. Here, we expanded our association panel size from 368 to 513 inbred lines with 0.5 million high quality SNPs using a two-step data-imputation method which combines identity by descent (IBD) based projection and k-nearest neighbor (KNN) algorithm. Genome-wide association studies (GWAS) were carried out for 17 agronomic traits with a panel of 513 inbred lines applying both mixed linear model (MLM) and a new method, the Anderson-Darling (A-D) test. Ten loci for five traits were identified using the MLM method at the Bonferroni-corrected threshold −log10 (P) >5.74 (α = 1). Many loci ranging from one to 34 loci (107 loci for plant height) were identified for 17 traits using the A-D test at the Bonferroni-corrected threshold −log10 (P) >7.05 (α = 0.05) using 556809 SNPs. Many known loci and new candidate loci were only observed by the A-D test, a few of which were also detected in independent linkage analysis. This study indicates that combining IBD based projection and KNN algorithm is an efficient imputation method for inferring large missing genotype segments. In addition, we showed that the A-D test is a useful complement for GWAS analysis of complex quantitative traits. Especially for traits with abnormal phenotype distribution, controlled by moderate effect loci or rare variations, the A-D test balances false positives and statistical power. The candidate SNPs and associated genes also provide a rich resource for maize genetics and breeding.

Low-threshold two-photon-pumped (TPP) perovskite microcavity lasers are achieved in crystal perovskite 1D or 2D microstructures fabricated through a liquid-phase self-assembly method assisted by two distinct surfactant soft templates. The lasing actions from the perovskite materials exhibit a shape-dependent microcavity effect, which is subsequently utilized for the modulation of the lasing modes and for the achievement of two-photon-pumped single-mode perovskite microlasers.

Most mycolic acid-containing actinobacteria and some proteobacteria use steroids as growth substrates, but the catabolism of the last two steroid rings has yet to be elucidated. In Mycobacterium tuberculosis, this pathway includes virulence determinants and has been proposed to be encoded by the KstR2-regulated genes, which include a predicted coenzyme A (CoA) transferase gene (ipdAB) and an acyl-CoA reductase gene (ipdC). In the presence of cholesterol, ΔipdC and ΔipdAB mutants of either M. tuberculosis or Rhodococcus jostii strain RHA1 accumulated previously undescribed metabolites: 3aα-H-4α(carboxyl-CoA)-5-hydroxy-7aβ-methylhexahydro-1-indanone (5-OH HIC-CoA) and (R)-2-(2-carboxyethyl)-3-methyl-6-oxocyclohex-1-ene-1-carboxyl-CoA (COCHEA-CoA), respectively. A ΔfadE32 mutant of Mycobacterium smegmatis accumulated 4-methyl-5-oxo-octanedioic acid (MOODA). Incubation of synthetic 5-OH HIC-CoA with purified IpdF, IpdC, and enoyl-CoA hydratase 20 (EchA20), a crotonase superfamily member, yielded COCHEA-CoA and, upon further incubation with IpdAB and a CoA thiolase, yielded MOODA-CoA. Based on these studies, we propose a pathway for the final steps of steroid catabolism in which the 5-member ring is hydrolyzed by EchA20, followed by hydrolysis of the 6-member ring by IpdAB. Metabolites accumulated by ΔipdF and ΔechA20 mutants support the model. The conservation of these genes in known steroid-degrading bacteria suggests that the pathway is shared. This pathway further predicts that cholesterol catabolism yields four propionyl-CoAs, four acetyl-CoAs, one pyruvate, and one succinyl-CoA. Finally, a ΔipdAB M. tuberculosis mutant did not survive in macrophages and displayed severely depleted CoASH levels that correlated with a cholesterol-dependent toxicity. Our results together with the developed tools provide a basis for further elucidating bacterial steroid catabolism and virulence determinants in M. tuberculosis.

Few data are available on population genetic structure in nematode species, and little of the available data allows direct comparison of the genetic structures of species having di erent life cycles. Here we use mtDNA sequence data to describe the genetic structure of a heterorhabditid nematode, and compare results to published data on other nematode species. Heterorhabditis marelatus is a parasite of soil-dwelling insects. Its life cycle and local ecology should result in small e ective population sizes and restricted gene¯ow. As predicted, H. marelatus shows much lower mtDNA diversity within populations and over the species as a whole, and has a much more strongly subdivided population structure, than parasites of mobile vertebrate hosts. From data such as these we can begin to generalize about the e ects of life cycle variation on genetic structure in di erent nematode species.Keywords: e ective size, gene¯ow, Heterorhabditis, mitochondrial DNA, ND4. IntroductionWe still know little about the population genetic structure of most parasite species, the exceptions being mostly species of medical or agricultural importance (e.g. Lymbery et al., 1990; Tibayrenc et al., 1991;Day et al., 1992; Anderson et al., 1995; Blouin et al., 1995; Dybdahl & Lively, 1996; Babiker & Walliker, 1997; Blair et al., 1997). This oversight is surprising because data on genetic structure are necessary for understanding important evolutionary processes such as adaptation to host defences, host-race formation, speciation, and the evolution of resistance to drugs or vaccines. Nematodes in particular are a grossly understudied taxon. Even though nematodes are one of the most speciesrich, ecologically diverse and economically important taxa, we have information on genetic structure for only a handful of nematode species, and almost all of these are human or agricultural parasites (recently reviewed in Anderson et al., 1998). Virtually nothing is known of the genetic structure of any free-living nematode species (including Caenorhabditis elegans). Thus, more comparative studies on genetic structure in nematode species are clearly needed. Indeed, Hughes et al. (1997) speci®cally called for more data on nematodes in their recent review of patterns of population di erentiation in di erent taxa. Parasitic nematodes display a wide variety of life cycles and life histories. For example, they parasitize almost all groups of plants and animals, and occur in virtually every marine, terrestrial and freshwater habitat. Their breeding system can be obligately or facultatively amphimictic (two distinct sexes), parthenogenetic or hermaphroditic. They range from highly host-speci®c to undiscriminating, and vary in the presence or absence of free-living stages and intermediate hosts. How this diversity of life cycles in¯uences genetic structure in di erent nematode species is unknown. We currently have too few comparative data from which to make any but the simplest predictions.What is needed are comparative studies of the genetic structure of nematode s...

Salt stress triggers the overdose accumulation of reactive oxygen species (ROS) in crop plants, leading to severe oxidative damage to living tissues. MicroRNAs (miRNAs) act as master regulators orchestrating the stress responsive regulatory networks as well as salt tolerance. However, the fundamental roles of miRNAs in modulating salt tolerance in cereal crops, especially in salt-triggered ROS scavenging remain largely unknown. Through small RNA sequencing, a salt-responsive miRNA, miR172 was identified in rice. Further, by generating the miR172-overexpression or MIR172 gene loss-of-function mutant lines, the biological significance of miR172 and its downstream signaling pathways related to salt tolerance were defined. We demonstrated that miR172 is a positive regulator of salt tolerance in both rice and wheat. More interestingly, miR172a and miR172b, but not miR172c or miR172d are involved in salt stress response, emphasizing the functional differentiation within miR172 family members. Further evidence uncovers a novel miR172/IDS1 regulatory module that functions as a crucial molecular rheostat in maintaining ROS homeostasis during salt stress, mainly through balancing the expression of a group of ROS-scavenging genes. Our findings establish a direct molecular link between miRNAs and detoxification response in cereal crops for improving salt tolerance.

Janus/gradient actuating materials have become promising candidates for actuating devices. The fabrication of functional Janus gradient actuators remains a challenge. This paper presents a facile fabrication of a hydrophilic/hydrophobic Janus inverse opal actuator via gradient infiltration. The Janus characteristics of the fabricated actuator were attributed to gradient infiltration along the thickness of the film caused by the gradient light intensity and the distinct polymerization behavior of ionic liquids and methyl methacrylate in the methanol system. The Janus film demonstrated directional bending upon water vapor adsorption, with a bending angle approaching 1440° in 4 s, accompanied by structure color/optic signal alteration. The actuating behaviors were effectively modulated by changing the composition of the film and the solvent system. Promising applications of this Janus solvent actuator were demonstrated in two sets of tests: driving an engine and lifting cargo. This work provides insight into the design and fabrication of multifunctional humidity-actuating materials.

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After being domesticated from teosinte, cultivated maize ( Zea mays ssp. mays ) spread worldwide and now is one of the most important staple crops. Due to its tremendous phenotypic and genotypic diversity, maize also becomes to be one of the most widely used model plant species for fundamental research, with many important discoveries reported by maize researchers. Here, we provide an overview of the history of maize domestication and key genes controlling major domestication-related traits, review the currently available resources for functional genomics studies in maize, and discuss the functions of most of the maize genes that have been positionally cloned and can be used for crop improvement. Finally, we provide some perspectives on future directions regarding functional genomics research and the breeding of maize and other crops.