The genes that control mammalian programmed cell death are conserved across wide evolutionary distances. Although plant cells can undergo apoptosis-like cell death, plant homologs of mammalian regulators of apoptosis have, in general, not been found. This is in part due to the lack of primary sequence conservation between animal and putative plant regulators of apoptosis. Thus, alternative approaches beyond sequence similarities are required to find functional plant homologs of apoptosis regulators. Here, we present the results of using advanced bioinformatic tools to uncover the Arabidopsis family of BAG proteins. The mammalian BAG (Bcl-2-associated athanogene) proteins are a family of chaperone regulators that modulate a number of diverse processes ranging from proliferation to growth arrest and cell death. Such proteins are distinguished by a conserved BAG domain that directly interacts with Hsp70 and Hsc70 proteins to regulate their activity. Our searches of the Arabidopsis thaliana genome sequence revealed seven homologs of the BAG protein family. We further show that plant BAG family members are also multifunctional and remarkably similar to their animal counterparts, as they regulate apoptosis-like processes ranging from pathogen attack to abiotic stress and development. Programmed cell death (PCD)2 plays an indispensable role in development and physiology, but it is unclear whether the mechanisms governing PCD in both plants and animals are similar. The genes that control programmed cell death are conserved across wide evolutionary distances from Caenorhabditis elegans to humans (1), although whether such conservation extends to plants is unknown. PCD plays a normal physiological role in many plant processes, and although the biochemical mechanisms responsible for cell suicide in plants are largely unknown, a number of reports suggest similarities to animal PCD (reviewed in Ref. 2). Moreover, ectopic expression of certain animal anti-apoptotic genes in transgenic plants is known to confer protection from pathogens and other stresses by death suppression (3-5).The identification of homologs of animal cell death regulators is of considerable interest. However, to date, few endogenous plant genes that show significant sequence similarity to animal apoptotic genes have been identified. Examination of the completed genome sequence of Arabidopsis thaliana, as well as other partially or nearly complete plant genomes by tools such as BLAST and FASTA, has not revealed any apparent homologs to the core apoptosis regulators. This may be explained by high sequence divergence of functional plant homologs of animal apoptotic proteins. Therefore, one approach to identify candidate PCD modulators in plants is through advanced tools of bioinformatics. We describe the results of such efforts, viz. the identification and characterization of the BAG protein family of Arabidopsis by profilesequence (Pfam) and profile-profile (FFAS) algorithms.The BAG proteins are an evolutionarily conserved family of multifunctional proteins...

The oral bacterium Streptococcus mutans, strain JH1140, produces the antibiotic mutacin 1140. Mutacin 1140 belongs to a group of antibiotics called lanthipeptides. More specifically, mutacin 1140 is related to the epidermin type A(I) lanthipeptides. Mutagenesis experiments of this group of lanthipeptides have been primarily restricted to the posttranslationally modified mesolanthionine and 3-methyllanthionine residues. Site-directed mutagenesis of the core peptide of mutacin 1140 was performed using the suicide vector pVA891. Substitutions of the N-terminal residue, the charged residue in the hinge region, and residues in ring A and intertwined rings C and D were investigated. A truncation and insertion of residues in ring A and intertwined rings C and D were also performed to determine whether or not they would alter the antimicrobial activity of the producing strain. Bioassays revealed that five of 14 mutants studied had improved antimicrobial activity against the indicator strain Micrococcus luteus ATCC 10240. MICs against Streptococcus mutans UA159, Streptococcus pneumoniae ATCC 27336, Staphylococcus aureus ATCC 25923, Clostridium difficile UK1, and Micrococcus luteus ATCC 10240 were determined for three mutacin 1140 variants that had the most significant increases in bioactivity in the M. luteus bioassay. This mutagenesis study of the epidermin group of lanthipeptides shows that antimicrobial activity can be significantly improved.

The Potato virus X (PVX) triple gene block protein 3 (TGBp3), an 8-kDa membrane binding protein, aids virus movement and induces the unfolded protein response (UPR) during PVX infection. TGBp3 was expressed from the Tobacco mosaic virus (TMV) genome (TMV-p3), and we noted the up-regulation of SKP1 and several endoplasmic reticulum (ER)-resident chaperones, including the ER luminal binding protein (BiP), protein disulphide isomerase (PDI), calreticulin (CRT) and calmodulin (CAM). Local lesions were seen on leaves inoculated with TMV-p3, but not TMV or PVX. Such lesions were the result of TGBp3-elicited programmed cell death (PCD), as shown by an increase in reactive oxygen species, DNA fragmentation and induction of SKP1 expression. UPR-related gene expression occurred within 8 h of TMV-p3 inoculation and declined before the onset of PCD. TGBp3-mediated cell death was suppressed in plants that overexpressed BiP, indicating that UPR induction by TGBp3 is a pro-survival mechanism. Anti-apoptotic genes Bcl-xl, CED-9 and Op-IAP were expressed in transgenic plants and suppressed N gene-mediated resistance to TMV, but failed to alleviate TGBp3-induced PCD. However, TGBp3-mediated cell death was reduced in SKP1-silenced Nicotiana benthamiana plants. The combined data suggest that TGBp3 triggers the UPR and elicits PCD in plants.

The widespread use of antibiotics drives the evolution of antimicrobial-resistant bacteria (ARB), threatening patients and healthcare professionals. Therefore, the development of novel strategies to combat resistance is recognized as a global healthcare priority. The two methods to combat ARB are development of new antibiotics or reduction in existing resistances. Development of novel antibiotics is a laborious and slow-progressing task that is no longer a safe reserve against looming risks. In this research, we suggest a method for reducing resistance to extend the efficacious lifetime of current antibiotics. Antimicrobial photodynamic therapy (aPDT) is used to generate reactive oxygen species (ROS) via the photoactivation of a photosensitizer. ROS then nonspecifically damage cellular components, leading to general impairment and cell death. Here, we test the hypothesis that concurrent treatment of bacteria with antibiotics and aPDT achieves an additive effect in the elimination of ARB. Performing aPDT with the photosensitizer methylene blue in combination with antibiotics chloramphenicol and tetracycline results in significant reductions in resistance for two methicillin-resistant Staphylococcus aureus (MRSA) strains, USA300 and RN4220. Additional resistant S. aureus strain and antibiotic combinations reveal similar results. Taken together, these results suggest that concurrent aPDT consistently decreases S. aureus resistance by improving susceptibility to antibiotic treatment. In turn, this development exhibits an alternative to overcome some of the growing MRSA challenge.

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