BackgroundMicroRNAs (miRNAs) are a new class of endogenous small RNAs that play essential regulatory roles in plant growth, development and stress response. Extensive studies of miRNAs have been performed in model plants such as rice, Arabidopsis thaliana and other plants. However, the number of miRNAs discovered in maize is relatively low and little is known about miRNAs involved in the very early stage during seed germination.ResultsIn this study, a small RNA library from maize seed 24 hours after imbibition was sequenced by the Solexa technology. A total of 11,338,273 reads were obtained. 1,047,447 total reads representing 431 unique sRNAs matched to known maize miRNAs. Further analysis confirmed the authenticity of 115 known miRNAs belonging to 24 miRNA families and the discovery of 167 novel miRNAs in maize. Both the known and the novel miRNAs were confirmed by sequencing of a second small RNA library constructed the same way as the one used in the first sequencing. We also found 10 miRNAs that had not been reported in maize, but had been reported in other plant species. All novel sequences had not been earlier described in other plant species. In addition, seven miRNA* sequences were also obtained. Putative targets for 106 novel miRNAs were successfully predicted. Our results indicated that miRNA-mediated gene expression regulation is present in maize imbibed seed.ConclusionsThis study led to the confirmation of the authenticity of 115 known miRNAs and the discovery of 167 novel miRNAs in maize. Identification of novel miRNAs resulted in significant enrichment of the repertoire of maize miRNAs and provided insights into miRNA regulation of genes expressed in imbibed seed.

Seed germination plays a pivotal role during the life cycle of plants. As dry seeds imbibe water, the resumption of energy metabolism and cellular repair occur and miRNA-mediated gene expression regulation is involved in the reactivation events. This research was aimed at understanding the role of miRNA in the molecular control during seed imbibition process. Small RNA libraries constructed from dry and imbibed maize seed embryos were sequenced using the Illumina platform. Twenty-four conserved miRNA families were identified in both libraries. Sixteen of them showed significant expression differences between dry and imbibed seeds. Twelve miRNA families, miR156, miR159, miR164, miR166, miR167, miR168, miR169, miR172, miR319, miR393, miR394 and miR397, were significantly down-regulated; while four families, miR398, miR408, miR528 and miR529, were significantly up-regulated in imbibed seeds compared to that in dry seeds. Furthermore, putative novel maize miRNAs and their target genes were predicted. Target gene GO analysis was performed for novel miRNAs that were sequenced more than 50 times in the normalized libraries. The result showed that carbohydrate catabolic related genes were specifically enriched in the dry seed, while in imbibed seed target gene enrichment covered a broad range of functional categories including genes in amino acid biosynthesis, isomerase activity, ligase activity and others. The sequencing results were partially validated by quantitative RT-PCR for both conserved and novel miRNAs and the predicted target genes. Our data suggested that diverse and complex miRNAs are involved in the seed imbibition process. That miRNA are involved in plant hormone regulation may play important roles during the dry-imbibed seed transition.

Cross-incompatibility genes known as gametophyte factors (ga) are numerous in maize. Many popcorn strains carry these genes and cannot be fertilized by pollen of dent and flint maize strains although the reciprocal crosses are successful. A Chinese popcorn strain SDGa25 carries the strongest allele of Ga1 (Ga1-S) and the majority of Chinese dent and flint maize germplasm are incompatible with SDGa25. The incompatibility is due to pollen tube growth obstruction 2 h after pollination. The pollen tube is arrested in the silk segment 5.5 cm distal to the pollination area and never reaches the ovule. The Ga1-S carried by SDGa25 behaves as a single dominant gene. This gene was mapped between markers SD3 on BAC AC200747 0.827 cM apart on the telomere side and SD12 on BAC AC204382 0.709 cM apart on the centromere side. The genetic region mapped spanning the Ga1-S locus was estimated to be 1.5 cM in length and the physical distance is 2,056,343 bp on ctg156 based on the B73 RefGen_v2 sequence. Gametophyte factors influence gene flow direction and the strongest Ga1-S allele is useful for isolating one category of commercial varieties from another. The eight tightly linked markers to Ga1-S developed in this study would greatly improve marker-assisted introgression efficiency and the fine mapping would facilitate the isolation of the Ga1-S.

Salinity is a major abiotic stress that limits plant productivity and quality throughout the world. Roots are the sites of salt uptake. To better understand salt stress responses in maize, we performed a comparative proteomic analysis of seedling roots from the salt-tolerant genotype F63 and the salt-sensitive genotype F35 under 160 mM NaCl treatment for 2 days. Under salinity conditions, the shoot fresh weight and relative water content were significantly higher in F63 than in F35, while the osmotic potential was significantly lower and the reduction of the K+/Na+ ratio was significantly less pronounced in F63 than in F35. Using an iTRAQ approach, twenty-eight proteins showed more than 2.0- fold changes in abundance and were regarded as salt-responsive proteins. Among them, twenty-two were specifically regulated in F63 but remained constant in F35. These proteins were mainly involved in signal processing, water conservation, protein synthesis and biotic cross-tolerance, and could be the major contributors to the tolerant genotype of F63. Functional analysis of a salt-responsive protein was performed in yeast as a case study to confirm the salt-related functions of detected proteins. Taken together, the results of this study may be helpful for further elucidating salt tolerance mechanisms in maize.

873 RESEARCHM aize (Zea mays L.) is a cross-pollinating crop and the level of cross-fertilization among maize plants of neighboring fields is very high due to a heavy volume of pollen produced by the maize plant and factors such as wind and insects that facilitate pollen traveling. Many field experiments have been performed to study the cross-fertilization rate of maize (Henry et al. ABSTRACTPhenotyping of a mapping population is usually the bottleneck that limits the size of the mapping population and mapping resolution. A homogeneous population mapping approach was used for mapping maize (Zea mays L.) gametophytic factor 1 (ga1) that could completely eliminate phenotyping during the mapping process. The strong allele of maize ga1 (Ga1-S), from popcorn inbred line SDGa25, showed a 100% cross-incompatibility with the majority of Chinese dent and flint maize. A homogeneous mapping population was developed by crossing an (SDGa25/Jing66) F 1 male back to an SDGa25 female. During the pollination process, pollen grains of ga1 were completely excluded from fertilization, and a homogeneous BC 1 F 1 (SDGa25//SDGa25/Jing66) population was created in which only the Ga1-S/Ga1-S genotype existed, making phenotyping unnecessary. A total of 2245 individuals of this population were genotyped with SD9 and SD12 markers and 20 recombinants were identified. The Ga1-S locus was quickly delineated to a 100 Kb region between markers dCS1 and insertion deletion ID7 at position 9,491,422 and 9,591,946 bp based on the B73 RefGen_v2 sequence. By markerassisted selection, Ga1-S was introgressed into parental lines of an elite white waxy maize hybrid by six generations of backcrossing and one generation of selfing. The homozygous Ga1-S/Ga1-S hybrid showed full cross-incompatibility to ga1 maize. The Ga1-S allele could be used as a biological reproductive barrier in reducing crosspollination between different types of maize such as waxy and non-waxy, genetically modified (GM) and non-GM maize.

Sex-determining region Y-box 2 (SOX2), as a subunit of transcription and reprogramming factor, plays a critical role in the development and progression of many malignancies, including lung cancer through gene amplification. In the present study, we aimed to quantify the levels of serum SOX2 DNA, analyze its diagnostic value and compare it with existing clinical parameters in lung cancer, and purpose to provide a novel tumor marker for lung cancer. Serum DNA was extracted from 94 lung cancer patients, 10 benign lung diseases, and 30 healthy volunteers, and then the levels of SOX2 DNA were quantified using real-time fluorescent quantitative polymerase chain reaction (FQ-PCR). The data were analyzed by statistical software SPSS14.0. The present results show that serum SOX2 DNA level in lung cancer group was higher compared to the levels in benign lung diseases group (u = 102.0, p < 0.001) or healthy group (u = 140.0, p < 0.001), and it was closely associated with TNM stage, histopathological type, and tumor size (p = 0.031, p = 0.012, and p = 0.010, respectively). However, serum SOX2 DNA levels of lung cancer patients were not associated with age, gender, smoking status, lymph node metastasis, or tumor differentiation (p > 0.05). ROC curve showed a sensitivity of 78.9% and a specificity of 82.5% for the ability of serum SOX2 DNA to detect lung cancer at the cutoff value of 1,078.3 copies/ul. Furthermore, we assessed the associations of serum SOX2 levels with clinical existing lung tumor markers, such as squamous cell carcinoma antigen, cytokeratin fragment 21-1, and neuron-specific enolase. The sensitivity was increased from 24.9, 66.1, and 39.1 to 84.2, 92.8, and 87.5%, respectively, by the combination of serum SOX2 DNA. Taken together, quantification of serum SOX2 DNA by FQ-PCR may serve as a novel accessory diagnostic tool for the clinical screening and detection of lung cancer.

ObjectiveAlthough many works have been done, the objectively measured diagnostic biomarkers are not available. Thus, we conducted this study to identify potential biomarkers for objectively diagnosing depression and explore the role of gut microbiota in the onset of depression.MethodsMajor depressive disorder (MDD) patients (n=56) and demographic data-matched healthy controls (HCs) (n=56) were included in this study. The gut microbiota in fecal samples and inflammation-related factors in serum were measured. Both univariate and multivariate statistical analyses were performed to identify the differential gut microbiota and inflammation-related factors.ResultsFinally, 46 differential operational taxonomic units (OTUs) (60.9% OTUs belonging to Firmicutes) and ten differential inflammation-related factors were identified. Correlation analysis showed that there were significant correlations between 14 differential OTUs (9 OTUs belonging to Firmicutes and 5 OTUs belonging to family Lachnospiraceae under Firmicutes) and seven differential inflammation-related factors. Meanwhile, 14 differential OTUs (9 OTUs belonging to Firmicutes and 5 OTUs belonging to family Lachnospiraceae under Firmicutes) and five differential inflammation-related factors (adiponectin, apolipoprotein A1, alpha 1-antitrypsin, neutrophilicgranulocyte count/white blood cell count and basophil count) were significantly correlated to depression severity. A panel consisting of these five differential inflammation-related factors could effectively diagnose MDD patients from HCs.ConclusionsOur results suggested that Firmicutes, especially family Lachnospiraceae, might play a role in the onset of depression via affecting the inflammation levels of host, and these five differential inflammation-related factors could be potential biomarkers for objectively diagnosing MDD.

By using the self-developed dynamic visualization photographic setup, this article investigated some major factors affecting the spray and combustion process of diesel engine fueled by biodiesel. The experimental results show: With the increase of biodiesel percentage, fuel injection advances slightly, the ignition delay becomes shorter and the duration of combustion lengthens. Engine speed has little effect on the spray. However, the combustion rate is increased and the burning time becomes shorter with the increase of engine speed, although the duration of combustion in terms of crank angle increases. With the increase of needle opening pressure, both the spray cone angle and the spray penetration of biodiesel increases, the atomization of spray improves, the ignition delay and the duration of combustion becomes shorter, the peak pressure increases