Abiotic and Biotic Stresses and Changes in the Lignin Content and Composition in Plants

Lignin is a polymer of phenylpropanoid compounds formed through a complex biosynthesis route, represented by a metabolic grid for which most of the genes involved have been sequenced in several plants, mainly in the model-plants Arabidopsis thaliana and Populus. Plants are exposed to different stresses, which may change lignin content and composition. In many cases, particularly for plant-microbe interactions, this has been suggested as defence responses of plants to the stress. Thus, understanding how a stressor modulates expression of the genes related with lignin biosynthesis may allow us to develop study-models to increase our knowledge on the metabolic control of lignin deposition in the cell wall. This review focuses on recent literature reporting on the main types of abiotic and biotic stresses that alter the biosynthesis of lignin in plants.     

Post-mating behavior, intramolt growth, and onset of migration to Chesapeake Bay spawning grounds by adult female blue crabs, Callinectes sapidus Rathbun

After molting to maturity, female blue crabs must rebuild muscles atrophied to permit molting and grow larger ones commensurate with the larger exoskeleton. They also must acquire energy for oogenesis and for migration to high-salinity spawning habitat, a distance of >150 km for females mating in the Upper Chesapeake Bay. Using telemetry and mark-recapture techniques, post-copulatory females in the upper bay were shown to forage at high rates, alternating between meandering and directed movement in the area of mating for weeks to months, and to begin migrating in October. Consequently, females from the Upper Chesapeake Bay probably do not spawn until the season after mating. Their priority seems to be to acquire energy before migrating. After molting, energy was allocated first into somatic tissue and eventually into hepatopancreas and gonads. Telemetry of feeding and movement showed that habitat utilization, traveling velocities, foraging patterns, and movements were similar to those already determined for males. However, females appeared to invest proportionally more energy (calories per gram dry weight) into their somatic and reproductive tissues than did males. A newly designed transmitter that telemetered depth showed that females moved during both ebbs and floods and remained at or near the bottom of the water column.     

Comparative effects of hepatocyte growth factor and epidermal growth factor on motility,morphology, mitogenesis,and signal transduction of primary rat hepatocytes

Hepatocyte growth factor (HGF) and epidermal growth factor (EGF) are major hepatacyte mitogens, but HGF, also known as scatter factor (SF), has also been shown as a potent motogen for epithelial and endothelial cells. The mechanisms by which HGF is a stronger motogen compared to other mitogens are not understood. Here we report a comparative study of the effect of the two growth factors on cultured primary rat hepatocytes regarding their differential effects on morphology, mitogenicity, and motility as well as the phosphorylation of cytoskeletal-associated proteins. Using three different motility assays, both HGF and EGF increased the motility of hepatocytes, but HGF consistently elicited a significantly greater motility response than EGF. Additionally, HGF induced a more flattened, highly spread morphology compared to EGF. To examine if HGF and EGF phosphorylated different cytoskeletal elements as signal transduction targets in view of the observed variation in morphology and motility, primary cultures of ³²P-loaded rat hepatocytes were stimulated by either HGF or EGF for up to 60 min. Both mitogens rapidly stimulated four isoforms of MAP kinase with similar kinetics and also rapidly facilitated the phosphorylation of cytoskeletal-associated F-actin. Two cytoskeletal-associated proteins, however, were observed to undergo rapid phosphorylation by HGF and not EGF during the time points described. One protein of 28 kDa was observed to become phosphorylated fivefold over controls, while the EGF-stimulated cells showed only a slight increase in the phosphorylation of this protein. Another protein with an apparent mwt of 42 kDa was phosphorylated 20-fold at 1 min and remained phosphorylated over 50-fold over control up to the 60 min time point. This protein was observed to become phosphorylated by EGF only after 10 min, and to a lesser extent (20-fold). Taken together, the data suggest that HGF and EGF stimulate divergent as well as redundant signal transduction pathways in the hepatocyte cytoskeleton, and this may result in unique HGF- or EGF-specific motility, morphology, and mitogenicity in hepatocytes. © 1994 Wiley-Liss, Inc.     

Type 2 oculocutaneous albinism (OCA2) in Zimbabwe and Cameroon: distribution of the 2.7-kb deletion allele of the P gene

In previous studies, we characterized a 2.7-kb interstitial deletion allele of the P gene associated with tyrosinase-positive oculocutaneous albinism (OCA2) in African Americans and Africans. In this study, we investigated the frequency of this allele among OCA2 subjects in two African countries, Zimbabwe and Cameroon. The deletion allele was most common in Zimbabwe, comprising nearly all (92%) mutant alleles, which is the highest incidence reported so far. In addition, the deletion allele was widespread but less common among OCA2 Cameroonians and accounted for 65% of the mutant alleles. Received: 20 March 1997 / Accepted: 8 May 1997     

A Pilot Study of Demographic and Dopaminergic Genetic Contributions to Weight Change in Kidney Transplant Recipients

Kidney transplant recipients often experience a significant amount of weight gain in the first year post-transplantation. While demographic factors such as age, race, and sex have been associated with weight gain in this population, these factors do not explain all of the variability seen. A number of studies have suggested that genetics also plays a critical role in weight changes. Recently, alterations in the activity of the neurotransmitter dopamine have been associated with weight change, and gene expression studies in kidney transplant recipients have supported this association. The purpose of this pilot study is to first examine the feasibility and methodology, and then to examine the associations of age, race, sex, and genotype for 13 SNPs and 3 VNTRs in 9 dopaminergic pathway genes (ANKK1, DRD2, DRD3, DRD4, SLC6A3/DAT1, MAOA, MAOB, COMT, CPE) for associations with percent weight change at 12 months post-transplantation. Seventy kidney transplant recipients had demographic and clinical data collected as a part of a larger observational study. DNA was extracted from repository buffy coat samples taken at the time of transplant, and genotyped using Taqman and PCR based methods. Three SNPs were independently associated with percent weight change: ANKK1 rs1800497 (r = -0.28, p = 0.05), SLC6A3/DAT1 rs6347 (p = 0.046), and CPE rs1946816 (p = 0.028). Stepwise regression modelling confirmed the combined associations of age (p = 0.0021), DRD4 VNTR 4/5 genotype (p = 0.0074), and SLC6A3/DAT1 rs6347 CC genotype (p = 0.0009) and TT genotype (p = 0.0004) with percent weight change in a smaller sample (n = 35) of these kidney transplant recipients that had complete genotyping. These associations indicate that there may be a genetic, and an age component to weight changes post transplantation.