Effects of coastal dynamics on colonization of Louisiana wetland plants by fungal endophytes

This dissertation explores the effects of stress and disturbance on fungal endophyte diversity and composition in obligate wetland plants in southeast Louisiana. I explored two types of endophytes: root and foliar. Each of these groups is known to live within apparently healthy host plants without causing symptoms of disease; therefore, plants are thought to benefit from this association. Few studies, however, have shown that plants in wetlands associate with fungi. In this dissertation, I show that both root and foliar endophytes not only exist in wetland plants living in flooded and saline environments, but also are abundant within these plants. In the chapter two I explore the distribution of arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) in the roots of 18 plant species. Monocots were mostly colonized by DSE, and dicots, including woody species were mostly colonized by AMF. In the third chapter, I used a mesocosm approach, to explore the effects of soil conditions on foliar endophyte diversity and composition in two wetland plant species – Sagittaria lancifolia and Taxodium distichum. Endophytes were abundant in both hosts, but S. lancifolia contained higher diversity. In addition, endophyte composition was shaped by different factors in each host: water quality shaped communities in T. distichum, and hydrology in S. lancifolia. In the fourth chapter I expand on the third chapter by including four more plant species that range from highly salt tolerant to intolerant and simulated a category 3 hurricane to explore its effects on endophytes within each plant species. I found that endophytes of grasses, irrespective of salt tolerance, did not change in diversity or composition following the simulated hurricane. Endophyte diversity T. distichum did not change, but composition was dependent on habitat type. Sagittaria lancifolia’s endophyte diversity decreased with hurricane conditions, but overall composition did not change. The results of these studies not only demonstrate that endophytes are present in wetland plants, but that they are abundant and common. Further, I show that host identity interacts with environmental conditions to influence diversity and composition and that habitat type is important in determining the outcome of endophyte composition after hurricanes

The β-secretase enzyme BACE1 as a therapeutic target for Alzheimer's disease

Amyloid plaques are defining histopathologic lesions in the brains of Alzheimer's disease (AD) patients and are composed of the amyloid-beta peptide, which is widely considered to play a critical role in the pathogenesis of AD. The β-secretase, or β-site amyloid precursor protein cleaving enzyme 1 (BACE1; also called Asp2, memapsin 2), is the enzyme that initiates the generation of amyloid beta. Consequently, BACE1 is an attractive drug target for lowering cerebral levels of amyloid beta for the treatment or prevention of AD. Much has been learned about BACE1 since its discovery over 10 years ago. In the present article, we review BACE1 properties and characteristics, cell biology, in vivo validation, substrates, therapeutic potential, and inhibitor drug development. Studies relating to the physiological functions of BACE1 and the promise of BACE1 inhibition for AD will also be discussed. We conclude that therapeutic inhibition of BACE1 should be efficacious for AD, although careful titration of the drug dose may be necessary to limit mechanism-based side effects

BACE1 RNAi restores the composition of phosphatidylethanolamine-derivates related to memory improvement in aged 3xTg-AD mice

ABSTRACT: β-amyloid (Aβ) is produced by the β-secretase 1 (BACE1)-mediated enzymatic cleavage of the amyloid precursor protein through the amyloidogenic pathway, making BACE1 a therapeutic target against Alzheimer’s disease (AD). Alterations in lipid metabolism are a risk factor for AD by an unknown mechanism. The objective of this study was to determine the effect of RNA interference against BACE1 (shBACEmiR) on the phospholipid profile in hippocampal CA1 area in aged 3xTg-AD mice after 6 and 12 months of treatment compared to aged PS1KI mice. The shBACEmiR treatment induced cognitive function recovery and restored mainly the fatty acid composition of lysophosphatidylethanolamine and etherphosphatidylethanolamine, reduced the cPLA2’s phosphorylation, down-regulated the levels of arachidonic acid and COX2 in the hippocampi of 3xTg-AD mice. Together, our findings suggest, for the first time, that BACE1 silencing restores phospholipids composition which could favor the recovery of cellular homeostasis and cognitive function in the hippocampus of triple transgenic AD mice. Keywords: Alzheimer’s disease, phospholipids, BACE1, RNA interference, hippocampus, cognitive functio

Shifts in Symbiotic Endophyte Communities of a Foundational Salt Marsh Grass Following Oil Exposure From the Deepwater Horizon Oil Spill

<p>Dataset for PLOSone paper</p

Melatonin Signal Transduction Pathways Require E-Box-Mediated Transcription of Per1 and Per2 to Reset the SCN Clock at Dusk.

Melatonin is released from the pineal gland into the circulatory system at night in the absence of light, acting as "hormone of darkness" to the brain and body. Melatonin also can regulate circadian phasing of the suprachiasmatic nucleus (SCN). During the day-to-night transition, melatonin exposure advances intrinsic SCN neural activity rhythms via the melatonin type-2 (MT2) receptor and downstream activation of protein kinase C (PKC). The effects of melatonin on SCN phasing have not been linked to daily changes in the expression of core genes that constitute the molecular framework of the circadian clock. Using real-time RT-PCR, we found that melatonin induces an increase in the expression of two clock genes, Period 1 (Per1) and Period 2 (Per2). This effect occurs at CT 10, when melatonin advances SCN phase, but not at CT 6, when it does not. Using anti-sense oligodeoxynucleotides (α ODNs) to Per 1 and Per 2, as well as to E-box enhancer sequences in the promoters of these genes, we show that their specific induction is necessary for the phase-altering effects of melatonin on SCN neural activity rhythms in the rat. These effects of melatonin on Per1 and Per2 were mediated by PKC. This is unlike day-active non-photic signals that reset the SCN clock by non-PCK signal transduction mechanisms and by decreasing Per1 expression. Rather, this finding extends roles for Per1 and Per2, which are critical to photic phase-resetting, to a nonphotic zeitgeber, melatonin, and suggest that the regulation of these clock gene transcripts is required for clock resetting by diverse regulatory cues

How abundant are root-colonizing fungi in southeastern Louisiana’s degraded marshes?Wetlands. 2010; 30(2):189–199. Endophyte Responses to Oil Exposure

Abstract Despite earlier notions that fungi are not important in wetlands, it is becoming clear that root endophytes are abundant in wetlands and potentially can influence plant community dynamics. Little is known about the effects of wetland degradation on these fungi. We assessed two groups of root endophytes in a degrading marsh in southeast Louisiana that historically was a swamp forest dominated by Taxodium distichum (baldcypress) and Nyssa aquatica (water tupelo). We determined percent root colonization by arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) in each of 18 vascular plant species. Fungi were present in all species that were assessed. In general, monocots were primarily colonized by DSE, whereas dicots were primarily colonized by AMF. Taxodium distichum was heavily colonized by AMF, as was the non-native, invasive Chinese tallow (Triadica sebifera). This study is the first to show that wetland plants in a degraded marsh harbor abundant and diverse root endophytes. These fungi and their interactions with stressed plants may be important in effective management of degrading wetlands