Characterization Of 'Fuzzy Tassel' Male Sterility Defects Implicates Novel MiRNA-Regulated Pathways In Maize Stamen Development

The maize 'fuzzy tassel' ('fzt') mutant is caused by a mutation in 'dicer-like1' and has broad developmental defects. 'dicer-like1' encodes a key enzyme for microRNA (miRNA) biogenesis and many miRNAs are reduced in 'fzt' plants. 'fzt' plants have reduced stature compared to normal siblings and make shorter, narrower leaves. 'fzt' also has striking inflorescence defects; the inflorescence meristem is fasciated, and other meristem types in the inflorescence are indeterminate. In addition, 'fzt' is male and female sterile. To further investigate the 'fzt' stamen defects, we compared development of 'fzt' and normal siblings stamens in fixed, sectioned tissue. Early stamen development in 'fzt' was indistinguishable from normal siblings. However, later in development, 'fzt' stamens arrested after microspores became vacuolated but before dehiscence. At maturity, some 'fzt' stamens contained pollen that appeared morphologically normal, but most of the pollen was dead based on Alexander staining. Normal pollen is tricellular at maturity; 'fzt' pollen was a mixture of uni-, bi-, and tri- cellular pollen, indicating pollen development was arrested at multiple developmental stages. Pollen in normal siblings is loaded with starch before dehiscence. 'fzt' pollen, however, failed to accumulate starch, suggesting pollen that developed to late stages arrested before maturity. I hypothesize that misexpression of specific miRNA targets underlies the 'fzt' stamen defects. The GAMYBs are regulated by miR159 and have key roles in stamen development in other species, and misexpression of the GAMYBs might contribute to male sterility in 'fzt'. 'ZmMyb74' and 'ZmMyb138' encode GAMYBs that are regulated by miR159. I obtained a transposon insertion allele in 'ZmMyb138' ('ZmMyb138-m1::Mu1') and two insertion alleles in 'ZmMyb74' ('ZmMyb74-m1::Mu1'; 'ZmMyb74-m2::Mu1'). Single mutants in both genes are phenotypically normal, suggesting these genes might function redundantly. I am generating ZmMyb138 ZmMyb74 double mutants for further analysis. Better characterization of the phenotype and molecular interactions of the GAMYBs has the potential for improving maize breeding systems in industry in a similar fashion to patented male sterile alleles that allow selectivity in hybrid corn breeding.M.S

Magnetic Field Measurement with Ground State Alignment

Observational studies of magnetic fields are crucial. We introduce a process "ground state alignment" as a new way to determine the magnetic field direction in diffuse medium. The alignment is due to anisotropic radiation impinging on the atom/ion. The consequence of the process is the polarization of spectral lines resulting from scattering and absorption from aligned atomic/ionic species with fine or hyperfine structure. The magnetic field induces precession and realign the atom/ion and therefore the polarization of the emitted or absorbed radiation reflects the direction of the magnetic field. The atoms get aligned at their low levels and, as the life-time of the atoms/ions we deal with is long, the alignment induced by anisotropic radiation is susceptible to extremely weak magnetic fields ($1{\rm G}\gtrsim B\gtrsim 10^{-15}$G). In fact, the effects of atomic/ionic alignment were studied in the laboratory decades ago, mostly in relation to the maser research. Recently, the atomic effect has been already detected in observations from circumstellar medium and this is a harbinger of future extensive magnetic field studies. A unique feature of the atomic realignment is that they can reveal the 3D orientation of magnetic field. In this article, we shall review the basic physical processes involved in atomic realignment. We shall also discuss its applications to interplanetary, circumstellar and interstellar magnetic fields. In addition, our research reveals that the polarization of the radiation arising from the transitions between fine and hyperfine states of the ground level can provide a unique diagnostics of magnetic fields in the Epoch of Reionization.Comment: 30 pages, 12 figures, chapter in Lecture Notes in Physics "Magnetic Fields in Diffuse Media". arXiv admin note: substantial text overlap with arXiv:1203.557

Natural images from the birthplace of the human eye

Here we introduce a database of calibrated natural images publicly available through an easy-to-use web interface. Using a Nikon D70 digital SLR camera, we acquired about 5000 six-megapixel images of Okavango Delta of Botswana, a tropical savanna habitat similar to where the human eye is thought to have evolved. Some sequences of images were captured unsystematically while following a baboon troop, while others were designed to vary a single parameter such as aperture, object distance, time of day or position on the horizon. Images are available in the raw RGB format and in grayscale. Images are also available in units relevant to the physiology of human cone photoreceptors, where pixel values represent the expected number of photoisomerizations per second for cones sensitive to long (L), medium (M) and short (S) wavelengths. This database is distributed under a Creative Commons Attribution-Noncommercial Unported license to facilitate research in computer vision, psychophysics of perception, and visual neuroscience.Comment: Submitted to PLoS ON

Identification of a Circadian Clock-Controlled Neural Pathway in the Rabbit Retina

Background: Although the circadian clock in the mammalian retina regulates many physiological processes in the retina, it is not known whether and how the clock controls the neuronal pathways involved in visual processing. Methodology/Principal Findings: By recording the light responses of rabbit axonless (A-type) horizontal cells under darkadapted conditions in both the day and night, we found that rod input to these cells was substantially increased at night under control conditions and following selective blockade of dopamine D2, but not D1, receptors during the day, so that the horizontal cells responded to very dim light at night but not in the day. Using neurobiotin tracer labeling, we also found that the extent of tracer coupling between rabbit rods and cones was more extensive during the night, compared to the day, and more extensive in the day following D 2 receptor blockade. Because A-type horizontal cells make synaptic contact exclusively with cones, these observations indicate that the circadian clock in the mammalian retina substantially increases rod input to A-type horizontal cells at night by enhancing rod-cone coupling. Moreover, the clock-induced increase in D2 receptor activation during the day decreases rod-cone coupling so that rod input to A-type horizontal cells is minimal. Conclusions/Significance: Considered together, these results identify the rod-cone gap junction as a key site in mammals through which the retinal clock, using dopamine activation of D2 receptors, controls signal flow in the day and night fro

Institutional and Individual Factors Affecting Scientists\u27 Data-Sharing Behaviors: A Multilevel Analysis

The objective of this research was to investigate the institutional and individual factors that influence scientists\u27 data-sharing behaviors across different scientific disciplines. Two theoretical perspectives, institutional theory, and theory of planned behavior, were employed in developing a research model that showed the complementary nature of the institutional and individual factors influencing scientists\u27 data-sharing behaviors. This research used a survey method to examine to what extent those institutional and individual factors influence scientists\u27 data-sharing behaviors in a range of scientific disciplines. A national survey (with 1,317 scientists in 43 disciplines) showed that regulative pressure by journals, normative pressure at a discipline level, and perceived career benefit and scholarly altruism at an individual level had significant positive relationships with data-sharing behaviors, and that perceived effort had a significant negative relationship. Regulative pressure by funding agencies and the availability of data repositories at a discipline level and perceived career risk at an individual level were not found to have any significant relationships with data-sharing behaviors

Analysis of the Maize dicer-like1 Mutant, fuzzy tassel, Implicates MicroRNAs in Anther Maturation and Dehiscence

Sexual reproduction in plants requires development of haploid gametophytes from somatic tissues. Pollen is the male gametophyte and develops within the stamen; defects in the somatic tissues of the stamen and in the male gametophyte itself can result in male sterility. The maize fuzzy tassel (fzt) mutant has a mutation in dicer-like1 (dcl1), which encodes a key enzyme required for microRNA (miRNA) biogenesis. Many miRNAs are reduced in fzt, and fzt mutants exhibit a broad range of developmental defects, including male sterility. To gain further insight into the roles of miRNAs in maize stamen development, we conducted a detailed analysis of the male sterility defects in fzt mutants. Early development was normal in fzt mutant anthers, however fzt anthers arrested in late stages of anther maturation and did not dehisce. A minority of locules in fzt anthers also exhibited anther wall defects. At maturity, very little pollen in fzt anthers was viable or able to germinate. Normal pollen is tricellular at maturity; pollen from fzt anthers included a mixture of unicellular, bicellular, and tricellular pollen. Pollen from normal anthers is loaded with starch before dehiscence, however pollen from fzt anthers failed to accumulate starch. Our results indicate an absolute requirement for miRNAs in the final stages of anther and pollen maturation in maize. Anther wall defects also suggest that miRNAs have key roles earlier in anther development. We discuss candidate miRNAs and pathways that might underlie fzt anther defects, and also note that male sterility in fzt resembles water deficit-induced male sterility, highlighting a possible link between development and stress responses in plants.ECU Open Access Publishing Support Fun

Large-Scale Controls of the Surface Water Balance Over Land-Insights From a Systematic Review and Meta-Analysis

The long-term surface water balance over land is described by the partitioning of precipitation (P) into runoff and evapotranspiration (ET), and is commonly characterized by the ratio ET/P. The ratio between potential evapotranspiration (PET) and P is explicitly considered to be the primary control of ET/P within the Budyko framework, whereas all other controls are often integrated into a single parameter, ω. Although the joint effect of these additional controlling factors of ET/P can be significant, a detailed understanding of them is yet to be achieved. This study therefore introduces a new global dataset for the long-term mean partitioning of P into ET and runoff in 2733 catchments, which is based on in-situ observations and assembled from a systematic examination of peer-reviewed studies. A total of 26 controls of ET/P that are proposed in the literature are assessed using the new dataset. Results reveal that: (i) factors controlling ET/P vary between regions with different climate types; (ii) controls other than PET/P explain at least 35% of the ET/P variance in all regions, and up to ∼90% in arid climates; (iii) among these, climate factors and catchment slope dominate over other landscape characteristics; and (iv) despite the high attention that vegetation-related indices receive as controls of ET/P, they are found to play a minor and often non-significant role. Overall, this study provides a comprehensive picture on factors controlling the partitioning of P, with valuable insights for model development, watershed management, and the assessment of water resources around the globe

The short term effects of straight leg raise neurodynamic treatment on pressure pain and vibration thresholds in individuals with spinally referred leg pain

Limited research exists for the effects of neurodynamic treatment techniques. Understanding short term physiological outcomes could help to better understand immediate benefits or harm of treatment. Objectives To assess the short-term effects of a straight leg raise (SLR) tensioner on pressure pain thresholds (PPT) and vibration thresholds (VT), and establish if additional factors influence outcome in individuals with spinally referred leg pain. Design Experimental, repeated measures. Methods Sixty seven participants (mean age (SD) 52.9 (13.3), 33 female) with spinally referred leg pain were divided into 3 sub-groups: somatic referred pain, radicular pain and radiculopathy. Individuals were assessed for central sensitisation (CS) and completed 5 disability and psychosocial questionnaires. PPT and VT were measured pre and post a 3 x 1 minute SLR tensioner intervention. Results No significant differences (p>0.05) were found between the 3 groups for either outcome measure, or after treatment. Slight improvements in VT were seen in the radiculopathy group after treatment, but were not significant. Only 2 participants were identified with CS. Disability and psychological factors were not significantly different at baseline between the 3 sub-groups, and did not correlate with the outcome measures. Conclusions No beneficial effects of treatment were found, but the trend for a decrease in VT indicated that even in individuals with radiculopathy, no detrimental changes to nerve function occurred. Psychosocial factors and levels of disability did not influence short term outcome of SLR treatment

Design of a Trichromatic Cone Array

Cones with peak sensitivity to light at long (L), medium (M) and short (S) wavelengths are unequal in number on the human retina: S cones are rare (<10%) while increasing in fraction from center to periphery, and the L/M cone proportions are highly variable between individuals. What optical properties of the eye, and statistical properties of natural scenes, might drive this organization? We found that the spatial-chromatic structure of natural scenes was largely symmetric between the L, M and S sensitivity bands. Given this symmetry, short wavelength attenuation by ocular media gave L/M cones a modest signal-to-noise advantage, which was amplified, especially in the denser central retina, by long-wavelength accommodation of the lens. Meanwhile, total information represented by the cone mosaic remained relatively insensitive to L/M proportions. Thus, the observed cone array design along with a long-wavelength accommodated lens provides a selective advantage: it is maximally informative