Molecular Studies to Evaluate Variegation of Philodendron var. Birkin - Are Genetic Mutations Responsible for Variegation in Philodendron Birkin?

Plant tissue culture and molecular genetic techniques were used to analyze the instability of the genome in philodendron var. \u27Birkin\u27. This plant has variegated, white, green, and greenish-red leaves (that have lost their variegation) on the same plant. Did genetic mutations occur in meristematic sectors of variegated leaves that have reverted to green coloration, or is it an epigenetic change?  PCR and sets of RAPD plastid primers were used to determine if the presence or absence of a PCR product correlated with differences in leaf color and variegation (white, green-white, variegated, reddish green or green leaves). A DNA isolation procedure was optimized to extract PCR-quality plastid DNA from Philodendron leaves. A modified DNA extraction procedure (BABEC) was used to isolate plastid DNA. It resulted in a high yield of DNA as measured by the Nanodrop system. PCR was performed with eight different RAPD plastid primers (GB07, GB8, OPA19, OPA22, OPB22, OPC08, OPC12, RAPD primer #1, RAPD primer #2). Differences in PCR products were observed for five primers, while two primers resulted in no difference in PCR products. This indicated that genetic mutations resulted in differences in leaf color and variegation. We are not excluding the possibility that epigenetic changes also play a role in variegation, however, this has not yet been analyzed. These results could prove useful for breeding ornamental traits and introducing improvements into the genus Philodendron

Targeting the Ets Binding Site of the HER2/neu Promoter with Pyrrole-Imidazole Polyamides

Three DNA binding polyamides (1-3) were synthesized that bind with high affinity (Ka = 8.7·10^9 M^-1 to 1.4·10^10 M^-1) to two 7-base pair sequences overlapping the Ets DNA binding site (EBS; GAGGAA) within the regulatory region of the HER2/neu proximal promoter. As measured by electrophoretic mobility shift assay, polyamides binding to flanking elements upstream (1) or downstream (2 and 3) of the EBS were one to two orders of magnitude more effective than the natural product distamycin at inhibiting formation of complexes between the purified EBS protein, epithelial restricted with serine box (ESX), and the HER2/neu promoter probe. One polyamide, 2, completely blocked Ets-DNA complex formation at 10 nM ligand concentration, whereas formation of activator protein-2-DNA complexes was unaffected at the activator protein-2 binding site immediately upstream of the HER2/neu EBS, even at 100 nM ligand concentration. At equilibrium, polyamide 1 was equally effective at inhibiting Ets/DNA binding when added before or after in vitro formation of protein-promoter complexes, demonstrating its utility to disrupt endogenous Ets-mediated HER2/neu preinitiation complexes. Polyamide 2, the most potent inhibitor of Ets-DNA complex formation by electrophoretic mobility shift assay, was also the most effective inhibitor of HER2/neu promoter-driven transcription measured in a cell-free system using nuclear extract from an ESX- and HER2/neu-overexpressing human breast cancer cell line, SKBR-3

Kinetics of Cleavage of Intra- and Extracellular Simian Virus 40 DNA with the Enediyne Anticancer Drug C- 1027

A kinetic analysis of cleavage of simian virus DNA (SV40 DNA) inside and outside green monkey BSC-I cells by the enediyne-protein antibiotic C-1027 and its free chromophore is described. Information on rate constants was obtained by fitting populations of forms I (closed circular DNA), II (nicked circular DNA) and III (linear DNA) of SV4f.J DNA as a function of drug concentration to a kinetic model which includes: cutting of form I to give form II with rate constant k1. cutting of form I to give form III with rate constant k4, and cutting of form II to give form III with rate constant k2. Theratio of single-strand (ss) to double-strand (ds) cutting for the holoantibiotic and the free chromophore. k1/k4, is approximately 1.8 for extracellular SV40 DNA. For intracellular DNA and extracellular DNA which has been post-treated with putrescine, ds cutting is much more probable, with k4, about four times as large as k1. This observation suggests that amine groups present in the cell are able to convert abasic sites opposite an ss break into a ds break in SV40 chkomatin. The overall rate of cleavage of form-1 DNA inside the cell is much larger than the rate outside, the sum k1 + k4 being about three times as large for intracellular DNA as for extracellular DNA

The Panchromatic Hubble Andromeda Treasury. Progression of Large-Scale Star Formation across Space and Time in M31

We investigate the clustering of early-type stars younger than 300 Myr on galactic scales in M31. Based on the stellar photometric catalogs of the Panchromatic Hubble Andromeda Treasury program that also provides stellar parameters derived from the individual energy distributions, our analysis is focused on the young stars in three star-forming regions, located at galactocentric distances of about 5, 10, and 15 kpc, corresponding to the inner spiral arms, the ring structure, and the outer arm, respectively. We apply the two-point correlation function to our selected sample to investigate the clustering behavior of these stars across different time- and length-scales. We find that young stellar structure survives across the whole extent of M31 longer than 300 Myr. Stellar distribution in all regions appears to be self-similar, with younger stars being systematically more strongly clustered than the older, which are more dispersed. The observed clustering is interpreted as being induced by turbulence, the driving source for which is probably gravitational instabilities driven by the spiral arms, which are stronger closer to the galactic centre.Comment: 10 pages, 5 figures. To appear in "LESSONS FROM THE LOCAL GROUP - A Conference in Honour of David Block and Bruce Elmegreen" eds. Freeman, K.C., Elmegreen, B.G., Block, D.L. & Woolway, M. (Springer: New York