TIR-NBS-LRR genes are rare in monocots: evidence from diverse monocot orders

Background: Plant resistance (R) gene products recognize pathogen effector molecules. Many R genes code for proteins containing nucleotide binding site (NBS) and C-terminal leucine-rich repeat (LRR) domains. NBS-LRR proteins can be divided into two groups, TIR-NBS-LRR and non-TIR-NBS-LRR, based on the structure of the N-terminal domain. Although both classes are clearly present in gymnosperms and eudicots, only non-TIR sequences have been found consistently in monocots. Since most studies in monocots have been limited to agriculturally important grasses, it is difficult to draw conclusions. The purpose of our study was to look for evidence of these sequences in additional monocot orders. Findings: Using degenerate PCR, we amplified NBS sequences from four monocot species (C. blanda, D. marginata, S. trifasciata, and Spathiphyllum sp.), a gymnosperm (C. revoluta) and a eudicot (C. canephora). We successfully amplified TIR-NBS-LRR sequences from dicot and gymnosperm DNA, but not from monocot DNA. Using databases, we obtained NBS sequences from additional monocots, magnoliids and basal angiosperms. TIR-type sequences were not present in monocot or magnoliid sequences, but were present in the basal angiosperms. Phylogenetic analysis supported a single TIR clade and multiple non-TIR clades. Conclusion: We were unable to find monocot TIR-NBS-LRR sequences by PCR amplification or database searches. In contrast to previous studies, our results represent five monocot orders (Poales, Zingiberales, Arecales, Asparagales, and Alismatales). Our results establish the presence of TIR-NBS-LRR sequences in basal angiosperms and suggest that although these sequences were present in early land plants, they have been reduced significantly in monocots and magnoliids

TIR-NBS-LRR genes are rare in monocots: evidence from diverse monocot orders

Background: Plant resistance (R) gene products recognize pathogen effector molecules. Many R genes code for proteins containing nucleotide binding site (NBS) and C-terminal leucine-rich repeat (LRR) domains. NBS-LRR proteins can be divided into two groups, TIR-NBS-LRR and non-TIR-NBS-LRR, based on the structure of the N-terminal domain. Although both classes are clearly present in gymnosperms and eudicots, only non-TIR sequences have been found consistently in monocots. Since most studies in monocots have been limited to agriculturally important grasses, it is difficult to draw conclusions. The purpose of our study was to look for evidence of these sequences in additional monocot orders. Findings: Using degenerate PCR, we amplified NBS sequences from four monocot species (C. blanda, D. marginata, S. trifasciata, and Spathiphyllum sp.), a gymnosperm (C. revoluta) and a eudicot (C. canephora). We successfully amplified TIR-NBS-LRR sequences from dicot and gymnosperm DNA, but not from monocot DNA. Using databases, we obtained NBS sequences from additional monocots, magnoliids and basal angiosperms. TIR-type sequences were not present in monocot or magnoliid sequences, but were present in the basal angiosperms. Phylogenetic analysis supported a single TIR clade and multiple non-TIR clades. Conclusion: We were unable to find monocot TIR-NBS-LRR sequences by PCR amplification or database searches. In contrast to previous studies, our results represent five monocot orders (Poales, Zingiberales, Arecales, Asparagales, and Alismatales). Our results establish the presence of TIR-NBS-LRR sequences in basal angiosperms and suggest that although these sequences were present in early land plants, they have been reduced significantly in monocots and magnoliids

Is there reduction in disease and predispersal seed predation at the border of a host plant’s range? - field and herbarium studies of Carex blanda

1. Small, isolated populations at species’ borders have been postulated to be less likely to have specialist pathogens and predators. Field and herbarium surveys were thus used to determine if two pathogens (a smut and a rust) and a predispersal seed predator were less common at the western range limit of the forest sedge Carex blanda in Kansas, USA. 2. Host plant size, reproduction, and density did not decline at the western border of the range. In fact, plants at two western sites had unusually large size and seed production. 3. Host populations at the edge of the range were more likely to be disease-free or lack the predispersal seed predator. Where the smut, seed predator, and rust were found, the proportion of infected or infested plants was not related to longitude, latitude, or percent forest cover. 4. More of the peripheral populations lacked the smut than the rust, as expected given the more localised nature of smut spore dispersal and the limited period when smut infection can occur. 5. In the adjacent, more highly forested state of Missouri, there were no geographic patterns in the incidence of the smut or seed predator in herbarium data. 6. The smut and rust increased in frequency over the 129 year span of herbarium collections. 7. Although field and herbarium distributional data were not identical (for example, smut infection was found much farther west in the field than in the herbarium data), the qualitative agreement between the two datasets suggests herbarium data can be used more broadly for studies of natural enemy distributions. 8. Limited dispersal by pathogens and seed predators is probably the reason why small, isolated western populations were less likely to have natural enemies. Peripheral host populations may thus have different ecological and evolutionary trajectories compared to more central populations. This conclusion, as well as the considerable variation among peripheral populations, is relevant to geographical studies of coevolution and to research on climatic effects on plants inhabiting ecotonal regions.National Science Foundation grant (NSF DEB0128810 to H.M.A, and REU supplement for S. P.); University of Kansas General Research Fund Grant (2301547-003); Educational Opportunity Award from University of Kansas Student Senate for S.P

E-Commerce and the Undergraduate MIS Curricula: an Exploratory Study

Undergraduate MIS curricula should reflect the popularity of e-commerce technologies in business practices. The study analyzes current trends of incorporating e-commerce content and skills into the undergraduate MIS curricula of AACSB accredited business schools. A definite trend to incorporate e-commerce knowledge and skills into the elective component of undergraduate MIS programs was found. Problems identified and possible solutions are discussed

Mammalian soil disturbance, plant cover, and soil nitrogen in a prairie restoration

Small mammal disturbances in tallgrass prairies are known to influence a variety of ecosystem properties, including plant establishment, plant diversity, and soil nutrient dynamics. We explored direct and indirect effects of mammalian soil disturbance on a newly established grassland restoration site. In 2016–2017, we measured variation in small mammal soil disturbance, plant cover, and total inorganic nitrogen, all within the same plots. Within our site, interior plots had greater disturbance than plots located near site edges. On average, plots with high soil disturbance in 2016 had high disturbance in 2017, and disturbance in the first year was greater than in the second year. Soil disturbance was associated with an overall decline in grass cover and an increase in forb cover (especially Asteraceae). However, there were no associations between soil disturbance and either inorganic nitrogen or plant species richness/diversity on the new restoration site. Our study supports the important link between prairie plant communities and small mammal soil disturbance, potentially creating heterogeneity that is important for tallgrass prairie restoration and conservation

Assessing the Influence of Temporal Autocorrelations on the Population Dynamics of a Disturbance Specialist Plant Population in a Random Environment

Biological populations are strongly influenced by random variations in their environment, which are often autocorrelated in time. For disturbance specialist plant populations, the frequency and intensity of environmental stochasticity (via disturbances) can drive the qualitative nature of their population dynamics. In this article, we extended our earlier model to explore the effect of temporally autocorrelated disturbances on population persistence. In our earlier work, we only assumed disturbances were independent and identically distributed in time. We proved that the plant seed bank population converges in distribution, and we showed that the mean and variance in seed bank population size were both increasing functions of the autocorrelation coefficient for all parameter values considered, but the interplay between increasing population size and increasing variability caused interesting relationships between quasi-extinction probability and autocorrelation. For example, for populations with low seed survival, fecundity, and disturbance frequency, increasingly positive autocorrelated disturbances decreased quasi-extinction probability. Higher disturbance frequency coupled with low seed survival and fecundity caused a nonmontone relationship between autocorrelation and quasi-extinction, where increasingly positive autocorrelations eventually caused an increase in quasi-extinction probability. For higher seed survival, fecundity, and/ or disturbance frequency, quasi-extinction probability was generally a monotonically increasing function of the autocorrelation coefficient

Differential Hox expression in murine embryonic stem cell models of normal and malignant hematopoiesis

The Hox family are master transcriptional regulators of developmental processes, including hematopoiesis. The Hox regulators, caudal homeobox factors (Cdx1-4), and Meis1, along with several individual Hox proteins, are implicated in stem cell expansion during embryonic development, with gene dosage playing a significant role in the overall function of the integrated Hox network. To investigate the role of this network in normal and aberrant, early hematopoiesis, we employed an in vitro embryonic stem cell differentiation system, which recapitulates mouse developmental hematopoiesis. Expression profiles of Hox, Pbx1, and Meis1 genes were quantified at distinct stages during the hematopoietic differentiation process and compared with the effects of expressing the leukemic oncogene Tel/PDGFR;2. During normal differentiation the Hoxa cluster, Pbx1 and Meis1 predominated, with a marked reduction in the majority of Hox genes (27/39) and Meis1 occurring during hematopoietic commitment. Only the posterior Hoxa cluster genes (a9, a10, a11, and a13) maintained or increased expression at the hematopoietic colony stage. Cdx4, Meis1, and a subset of Hox genes, including a7 and a9, were differentially expressed after short-term oncogenic (Tel/PDGFR;2) induction. Whereas Hoxa4-10, b1, b2, b4, and b9 were upregulated during oncogenic driven myelomonocytic differentiation. Heterodimers between Hoxa7/Hoxa9, Meis1, and Pbx have previously been implicated in regulating target genes involved in hematopoietic stem cell (HSC) expansion and leukemic progression. These results provide direct evidence that transcriptional flux through the Hox network occurs at very early stages during hematopoietic differentiation and validates embryonic stem cell models for gaining insights into the genetic regulation of normal and malignant hematopoiesis

Semi-stochastic models for Salmonella infection within finishing pig units in the UK

A multi-group semi-stochastic model is formulated to describe Salmonella dynamics on a pig herd within the UK and assess whether farm structure has any effect on the dynamics. The models include both direct transmission and indirect (via free-living infectious units in the environment and airborne infection). The basic reproduction number [Formula: see text] is also investigated. The models estimate approximately 24.6% and 25.4% of pigs at slaughter weight will be infected with Salmonella within a slatted-floored and solid-floored unit respectively, which corresponds to values found in previous abattoir and farm studies, suggesting that the model has reasonable validity. Analysis of the models identified the shedding rate to be of particular importance in the control of Salmonella spread, a finding also evident in an increase in the [Formula: see text] value

Seed fates in crop–wild hybrid sunflower: crop allele and maternal effects

Domestication has resulted in selection upon seed traits found in wild populations, yet crop-wild hybrids retain some aspects of both parental phenotypes. Seed fates of germination, dormancy, and mortality can influence the success of crop allele introgression in crop-wild hybrid zones, especially if crop alleles or crop-imparted seed coverings result in out-of-season germination. We performed a seed burial experiment using crop, wild, and diverse hybrid sunflower (Helianthus annuus) cross types to test how a cross type's maternal parent and nuclear genetic composition might affect its fate under field conditions. We observed higher maladaptive fall germination in the crop- and F1- produced seeds than wild-produced seeds and, due to an interaction with percent crop alleles, fall germination was higher for cross types with more crop-like nuclear genetics. By spring, crop-produced cross types had the highest overwintering mortality, primarily due to higher fall germination. Early spring germination was identical across maternal types, but germination continued for F1-produced seeds. In conclusion, the more wild-like the maternal parent or the less proportion of the cross type's genome contributed by the crop, the greater likelihood a seed will remain ungerminated than die. Wild-like dormancy may facilitate introgression through future recruitment from the soil seed bank

Population Dynamics and Genetics of Plant Disease: A Case Study of Anther-Smut Disease

This is the publisher's version, also available electronically from http://www.jstor.org/stable/info/2265569A model by Levin and Udovic (1977) emphasizes the need for integration of studies of the numerical abundances and genetic composition of host and pathogen species. We use their conceptual framework to summarize our collaborative research on the ecological genetics of the anther-smut disease of Silene alba caused by the fungus Ustilago violacea. Our theoretical investigations have revealed the importance of the rate and mode of disease transmission on the likelihood of coexistence between host and pathogen. Our empirical studies have quantified patterns of disease spread on local and regional spatial scales and have shown that host genotypes differ greatly in resistance. Comparable genetic variation in pathogen virulence has not yet been demonstrated. The genetic composition of host populations alters numerical dynamics in experimental populations: disease declines in resistant populations, while host and pathogen appear to coexist in susceptible populations. Ecological outcomes also may be affected by the negative relationship between disease incidence and host flowering time, which may constitute a "cost" to resistance. We are currently expanding our work on the ecology and genetics of metapopulation dynamics of host and pathogen