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61.
J. M. Kane K. A. Meinhardt T. Chang B. L. Cardall R. Michalet T. G. Whitham 《Plant Ecology》2011,212(5):733-741
Climate change-induced droughts have contributed to large-scale die-offs of dominant tree species throughout much of the southwestern
United States. These mortality events provide ecologists with the opportunity to determine whether afterlife effects associated
with the die-off occur and the potential implications for future ecosystem changes. We studied both the afterlife and interaction
effects of condition (dead trees, living trees, and open areas) on understory vegetation in a Juniperus monosperma woodland of northern Arizona 7 years after a major mortality event. Five major findings resulted: (1) there was a positive
afterlife effect on understory plants, in which vegetation under dead junipers contained almost double the amount of cover;
(2) the competitive effect on understory plants was exemplified by a 1.3 times greater cover and 1.6 additional species in
open areas compared to under living junipers; (3) plant community composition significantly differed by aspect and condition;
(4) the highly invasive cheatgrass (Bromus tectorum) was 1.5 times greater under dead junipers compared to live junipers; and (5) litter depth and light availability were negatively
and positively correlated with plant cover, respectively, but weakly correlated with afterlife effects. Our results indicate
that mortality events can promote changes in understory vegetation through afterlife effects. In ecosystems where foundation
species suffer high rates of mortality, changes in plant population dynamics and ecosystem function may promote an altered
trajectory in community composition with the potential to increase the presence of invasive species. Continued species die-offs
associated with climate change-induced drought may contribute to an increased occurrence and legacy of afterlife effects. 相似文献
62.
63.
Luke M. Evans Gerard J. Allan Nashelly Meneses Tamara L. Max Thomas G. Whitham 《Evolutionary ecology》2013,27(1):65-81
Herbivore adaptation to plant genetic variation can lead to reproductive isolation and the formation of host-associated lineages (host-associated differentiation, or HAD). Plant genetic variation exists along a scale, ranging from variation among individual plant genotypes to variation among plant species. Along this scale, herbivores may adapt and diverge at any level, yet few studies have examined whether herbivore differentiation exhibits scaling with respect to host variation (e.g., from genotypes to species). Determining at which level(s) herbivore differentiation occurs can provide insight into the importance of plant genetic variation on herbivore evolution. Previous studies have found strong genetic differentiation in the eriophyid mite, Aceria parapopuli, between hybrid Populus hosts and parental Populus species, but minimal neutral-locus differentiation among individual trees of the same species. We tested whether genetic differentiation in A. parapopuli scales with genetic variation in its Populus hosts. Using mite ITS1 sequence data collected among host species and among host populations, two key patterns emerged. (1) We found strong differentiation of A. parapopuli among Populus species, supporting the hypothesis that plant species differences drive reproductive isolation and HAD. (2) We did not find evidence of host-driven genetic differentiation in mites at the level of plant populations, suggesting that this level of plant variation is insufficiently strong to drive differentiation at a neutral locus. In combination with previous studies, we found that HAD occurs at the higher levels of plant genetic variation, but not at lower levels, and conclude that HAD depends on the scale of plant genetic variation examined. 相似文献
64.
Andrew J. Solomon William Hills Zunqiu Chen James Rosenbaum Dennis Bourdette Ruth Whitham 《PloS one》2013,8(6)
Background
Rheumatologic diseases may cause neurologic disorders that mimic multiple sclerosis (MS). A panel of serum autoantibodies is often obtained as part of the evaluation of patients suspected of having MS.Objectives
To determine, in light of recently revised diagnostic criteria for MS, neuromyelitis optica, and Sjogren’s Syndrome, if testing for autoantibodies in patients with a confirmed diagnosis of MS would reveal a frequency or demonstrate a clinical utility divergent from previous reports or lead to identification of undiagnosed cases of Sjogren’s Syndrome.Methods
Convenience sample cross-sectional study of MS patients recruited from the OHSU Multiple Sclerosis Center.Results
Autoantibodies were detected in 38% (35/91) of patients with MS and were not significantly associated with disease characteristics or severity. While four patients had SSA antibodies, none met diagnostic criteria for Sjogren’s Syndrome.Conclusions
Rheumatologic autoantibodies are frequently found in MS patients and are not associated with disease severity or systemic rheumatologic disease. Our demonstration of the low specificity of these autoantibodies suggests that the diagnostic utility and cost-effectiveness of testing is not supported when there is strong clinical suspicion of MS and low clinical suspicion of rheumatologic disease. 相似文献65.
Cheng NH Liu JZ Liu X Wu Q Thompson SM Lin J Chang J Whitham SA Park S Cohen JD Hirschi KD 《The Journal of biological chemistry》2011,286(23):20398-20406
Global environmental temperature changes threaten innumerable plant species. Although various signaling networks regulate plant responses to temperature fluctuations, the mechanisms unifying these diverse processes are largely unknown. Here, we demonstrate that an Arabidopsis monothiol glutaredoxin, AtGRXS17 (At4g04950), plays a critical role in redox homeostasis and hormone perception to mediate temperature-dependent postembryonic growth. AtGRXS17 expression was induced by elevated temperatures. Lines altered in AtGRXS17 expression were hypersensitive to elevated temperatures and phenocopied mutants altered in the perception of the phytohormone auxin. We show that auxin sensitivity and polar auxin transport were perturbed in these mutants, whereas auxin biosynthesis was not altered. In addition, atgrxs17 plants displayed phenotypes consistent with defects in proliferation and/or cell cycle control while accumulating higher levels of reactive oxygen species and cellular membrane damage under high temperature. Together, our findings provide a nexus between reactive oxygen species homeostasis, auxin signaling, and temperature responses. 相似文献
66.
Melissa Bredow Martha Ibore Natukunda Bliss M. Beernink Aline Sartor Chicowski Maria G. SalasFernandez Steven A. Whitham 《Molecular Plant Pathology》2023,24(1):71
Sorghum is vulnerable to many biotic and abiotic stresses, which cause considerable yield losses globally. Efforts to genetically characterize beneficial sorghum traits, including disease resistance, plant architecture, and tolerance to abiotic stresses, are ongoing. One challenge faced by sorghum researchers is its recalcitrance to transformation, which has slowed gene validation efforts and utilization for cultivar development. Here, we characterize the use of a foxtail mosaic virus (FoMV) vector for virus‐induced gene silencing (VIGS) by targeting two previously tested marker genes: phytoene desaturase (PDS) and ubiquitin (Ub). We additionally demonstrate VIGS of a subgroup of receptor‐like cytoplasmic kinases (RLCKs) and report the role of these genes as positive regulators of early defence signalling. Silencing of subgroup 8 RLCKs also resulted in higher susceptibility to the bacterial pathogens Pseudomonas syringae pv. syringae (B728a) and Xanthomonas vasicola pv. holcicola, demonstrating the role of these genes in host defence against bacterial pathogens. Together, this work highlights the utility of FoMV‐induced gene silencing in the characterization of genes mediating defence responses in sorghum. Moreover, FoMV was able to systemically infect six diverse sorghum genotypes with high efficiency at optimal temperatures for sorghum growth and therefore could be extrapolated to study additional traits of economic importance. 相似文献
67.
D.?G.?FischerEmail author S.?K.?Chapman A.?T.?Classen C.?A.?Gehring K.?C.?Grady J.?A.?Schweitzer T.?G.?Whitham 《Plant and Soil》2014,375(1-2):1-19
Background
Many biological questions about N availability and the N cycle require knowledge of the abundance and identity of molecules comprising the pool of organic N. Moreover, basic knowledge of the molecular composition of the soil solution can give rise to new hypotheses via data-driven or inductive reasoning.Scope
This paper examines the composition of organic N molecules in the soil solution. Our perception of organic N in the soil solution is shaped by analytical approaches, and thus I briefly review approaches for sampling and analysis of the soil solution. I give examples of hypotheses generated by knowledge of the molecular composition of organic N and conclude by suggesting priorities for future research.Conclusions
Studies of the molecular composition of organic N are very much in their infancy. Amino acids, their oligomers and polymers are consistently large components of the pool of organic N. The soil solution also contains organic N compounds from at least another 12 compound classes, but almost nothing is known about their functional significance. Uncovering the role of these other compounds in the N cycle would enrich our understanding of organic N and the N cycle, and place studies of amino acids and their polymers in a broader context. 相似文献68.
69.
Y Deng J Zhao D Sakurai KM Kaufman JC Edberg RP Kimberly DL Kamen GS Gilkeson CO Jacob RH Scofield CD Langefeld JA Kelly ME Alarcón-Riquelme BIOLUPUS GENLES Networks JB Harley TJ Vyse BI Freedman PM Gaffney KM Sivils JA James TB Niewold RM Cantor W Chen BH Hahn EE Brown PROFILE BP Tsao 《Arthritis research & therapy》2012,14(Z3):A5
70.
Alcoholism is a significant public health problem. A picture of the genetic architecture underlying alcohol-related phenotypes
is emerging from genome-wide association studies and work on genetically tractable model organisms. 相似文献