Subcellular localization and turnover of Arabidopsis phototropin 1

We reported recently that internalization of the plant blue light receptor phototropin 1 (phot1) from the plasma membrane in response to irradiation is reliant on receptor autophosphorylation. Pharmacological interference and co-immunoprecipitation analyses also indicated that light-induced internalization of phot1 involves clathrin-dependent processes. Here, we describe additional pharmacological studies that impact the subcellular localization and trafficking of Arabidopsis phot1. Alterations in the microtububle cytoskeleton led to dramatic differences in phot1 localization and function. Likewise, inhibition of phosphatidic acid (PA) signaling was found to impair phot1 localization and function. However, action of PA inhibition on phot1 function may be attributed to pleiotropic effects on cell growth. While phot1 kinase activation is necessary to stimulate its internalization, autophosphorylation is not required for phot1 turnover in response to prolonged blue light irradiation. The implications of these findings in regard to phot1 localization and function are discussed.Key words: phototropin 1 (phot1), phototropism, subcellular trafficking, autophosphorylation, protein turnover     

Synthesis of caged 2,3,3a,7a-tetrahydro-3,6-methanobenzofuran-7(6H)-ones: Evaluating the minimum structure for apoptosis induction by gambogic acid

We have reported the discovery of gambogic acid (GA) as a potent apoptosis inducer and the identification of transferrin receptor as its molecular target. In order to understand the basic pharmacophore of GA for inducing apoptosis and to discover novel and simplified derivatives as potential anti-cancer agents, we explored the synthesis of caged 2,3,3a,7a-tetrahydro-3,6-methanobenzofuran-7(6H)-ones (4-oxatricyclo[4.3.1.0]decan-2-ones). Three types of 2,3,3a,7a-tetrahydro-3,6-methanobenzofuran-7(6H)-ones based on xanthone, 2-phenylchromene-4-one and benzophenone, were synthesized using a Claisen/Diels-Alder reaction cascade. All the reactions produced the targeted caged compound as well as its neo-isomer. The caged compounds based on xanthone and 2-phenylchromene-4-one were found to maintain the apoptosis inducing and cell growth inhibiting activity of GA, although with less potency. The caged compounds based on benzophenone were found to be inactive. Our study determined the minimum structure of GA for its apoptosis inducing activity, which could lead to the development of simple derivatives as potential anti-cancer drugs.     

Molecular Epidemiology of Tuberculosis in Kaohsiung City Located at Southern Taiwan, 2000-2008

Background

We present the first comprehensive analysis of Mycobacterium tuberculosis (MTB) isolates circulating in southern Taiwan. In this 9-year population-based study, the TB situation in the Kaohsiung region was characterized by genotypic analysis of 421 MTB isolates.

Methods

All 421 isolates of MTB were analyzed by spoligotyping and MIRU-VNTR typing. Drug-resistance patterns were also analyzed.

Results

The percentage of EAI (East African-Indian) strains increased across sampling years (2000–2008) in southern Taiwan, whereas the proportion of Beijing lineages remained unchanged. Clustering was more frequent with EAI genotype infections (odds ratio = 3.6, p<0.0001) when compared to Beijing genotypes. Notably, MTB resistance to streptomycin (STR) had significantly increased over time, but resistance to other antibiotics, including multidrug resistance, had not. Three major genes (gidB, rpsL and rrs) implicated in STR resistance were sequenced and specific mutations identified.

Conclusions

This study revealed that EAI strains were highly transmissible and that STR resistance has increased between 2000 and 2008 in Kaohsiung, Taiwan.     

Tight clustering: a resampling-based approach for identifying stable and tight patterns in data

In this article, we propose a method for clustering that produces tight and stable clusters without forcing all points into clusters. The methodology is general but was initially motivated from cluster analysis of microarray experiments. Most current algorithms aim to assign all genes into clusters. For many biological studies, however, we are mainly interested in identifying the most informative, tight, and stable clusters of sizes, say, 20-60 genes for further investigation. We want to avoid the contamination of tightly regulated expression patterns of biologically relevant genes due to other genes whose expressions are only loosely compatible with these patterns. "Tight clustering" has been developed specifically to address this problem. It applies K-means clustering as an intermediate clustering engine. Early truncation of a hierarchical clustering tree is used to overcome the local minimum problem in K-means clustering. The tightest and most stable clusters are identified in a sequential manner through an analysis of the tendency of genes to be grouped together under repeated resampling. We validated this method in a simulated example and applied it to analyze a set of expression profiles in the study of embryonic stem cells.     

Investigation of seven Vibrio virulence genes among Vibrio alginolyticus and Vibrio parahaemolyticus strains from the coastal mariculture systems in Guangdong, China

AIMS: To investigate the distribution of the virulence of two Vibrio species among different strains obtained from the mariculture systems on the coast of Guangdong in China and the correlation between the virulence strains and the virulence genes among Vibrio alginolyticus. METHODS: Besides three strains, 72 V. alginolyticus strains and seven Vibrio parahaemolyticus strains were examined by PCR or semi-nested PCR for the virulence genes (tlh, trh, tdh, toxR, toxRS, ctxA, VPI). Additionally, the virulence of 18 V. alginolyticus strains was tested. SIGNIFICANCE AND IMPACT OF THE STUDY: Virulence genes homologous to those in the V. parahaemolyticus and Vibrio cholerae are widely distributed among V. alginolyticus and V. parahaemolyticus in the coastal mariculture systems in Guangdong, China. Some of the V. alginolyticus strains are pathogenic to aquatic animals, and might have derived their virulence genes from V. parahaemolyticus or V. cholerae, representing a possible reservoir of these genes. However, there is no correlation between presence and absence of the virulence genes used to investigate V. alginolyticus and its virulent strains. In this report, we also show that tlh is distributed among V. alginolyticus.