Herbicides are the foundation of weed control in commercial crop-production systems. However, herbicide-resistant (HR) weed populations are evolving rapidly as a natural response to selection pressure imposed by modern agricultural management activities. Mitigating the evolution of herbicide resistance depends on reducing selection through diversification of weed control techniques, minimizing the spread of resistance genes and genotypes via pollen or propagule dispersal, and eliminating additions of weed seed to the soil seedbank. Effective deployment of such a multifaceted approach will require shifting from the current concept of basing weed management on single-year economic thresholds.

Neurofibrillary tangles, composed of insoluble aggregates of the microtubule-associated protein Tau, are a pathological hallmark of Alzheimer disease (AD) and other tauopathies. However, recent evidence indicates that neuronal dysfunction precedes the formation of these insoluble fibrillar deposits, suggesting that earlier prefibrillar Tau aggregates may be neurotoxic. To determine the composition of these aggregates, we have employed a photochemical cross-linking technique to examine intermolecular interactions of full-length Tau in vitro. Using this method, we demonstrate that dimerization is an early event in the Tau aggregation process and that these dimers selfassociate to form larger oligomeric aggregates. Moreover, using these stabilized Tau aggregates as immunogens, we generated a monoclonal antibody that selectively recognizes Tau dimers and higher order oligomeric aggregates but shows little reactivity to Tau filaments in vitro. Immunostaining indicates that these dimers/oligomers are markedly elevated in AD, appearing in early pathological inclusions such as neuropil threads and pretangle neurons as well as colocalizing with other early markers of Tau pathogenesis. Taken as a whole, the work presented herein demonstrates the existence of alternative Tau aggregates that precede formation of fibrillar Tau pathologies and raises the possibility that these hierarchical oligomeric forms of Tau may contribute to neurodegeneration.

In little over 20 yr, Palmer amaranth has risen from relative obscurity to its current status as one of the most widespread, troublesome, and economically damaging agronomic weeds in the southeastern U.S. Numerous factors have enabled Palmer amaranth to become such a dominant and difficult-to-control weed, including its rapid growth rate, high fecundity, genetic diversity, ability to tolerate adverse conditions, and its facility for evolving herbicide resistance. It is both a serious threat to several U.S. cropping systems and a fascinating model weed. In this paper, we review the growing body of literature on Palmer amaranth to summarize the current state of knowledge on the biology, agricultural impacts, and management of this weed, and we suggest future directions for research.

Anopheles gambiae, the primary African vector of malaria parasites, exhibits numerous rhythmic behaviors including flight activity, swarming, mating, host seeking, egg laying, and sugar feeding. However, little work has been performed to elucidate the molecular basis for these daily rhythms. To study how gene expression is regulated globally by diel and circadian mechanisms, we have undertaken a DNA microarray analysis of An. gambiae under light/ dark cycle (LD) and constant dark (DD) conditions. Adult mated, non-blood-fed female mosquitoes were collected every 4 h for 48 h, and samples were processed with DNA microarrays. Using a cosine wave-fitting algorithm, we identified 1,293 and 600 rhythmic genes with a period length of 20-28 h in the head and body, respectively, under LD conditions, representing 9.7 and 4.5% of the An. gambiae gene set. A majority of these genes was specific to heads or bodies. Examination of mosquitoes under DD conditions revealed that rhythmic programming of the transcriptome is dependent on an interaction between the endogenous clock and extrinsic regulation by the LD cycle. A subset of genes, including the canonical clock components, was expressed rhythmically under both environmental conditions. A majority of genes had peak expression clustered around the day/night transitions, anticipating dawn and dusk. Genes cover diverse biological processes such as transcription/translation, metabolism, detoxification, olfaction, vision, cuticle regulation, and immunity, and include rate-limiting steps in the pathways. This study highlights the fundamental roles that both the circadian clock and light play in the physiology of this important insect vector and suggests targets for intervention.

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