Systematics within Gyps vultures: a clade at risk

Background  

Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis.     

Photoacoustic Study of Changes in the Energy Storage of Photosystems I and II during State 1-State 2 Transitions

Using photoacoustic spectroscopy, state 1-state 2 transitions were demonstrated in vivo in intact sugar maple leaves (Acer saccharum Marsh.) by following the changes in energy storage of photosystems (PS) I and II. Energy storage measured with 650 nm modulated light (light 2) in the presence of background white light indicated the total energy stored by both photosystems (ES_t), and in the presence of background far-red light showed the energy stored by PSI (ES_psi). The difference between ES_t and ES_psi gave the energy stored by PSII (ES_psii). While ES_t remained nearly constant during state transitions, both ES_psi and ES_psii changed considerably. The ratio of ES_psii to ES_psi, an indicator of the energy distribution between the two photosystems, decreased or increased during transition to state 2 or state 1, respectively. State transitions were completed in about 20 min and were fully reversible. During transition from state 1 to state 2, the fraction of excitation energy gained by PSI was nearly equal to that lost by PSII. This fraction of excitation energy transferred from PSII to PSI accounted for about 5% of the absorbed light (fluorescence is not considered), 19% of ES_t, 34% of ES_psii, and 43% of ES_psi in state 2. NaF treatment inhibited the transition to state 1. Data in the present study confirm the concept of changes in absorption cross-section of photosystems during state transitions.     

Patterns of divergence during evolution of alpha 1-proteinase inhibitors in mammals

alpha 1-Proteinase inhibitor (alpha 1-PI), a member of the serine proteinase inhibitor superfamily, has a primary role in controlling neutrophil elastase activity within the mammalian circulation. Several studies have indicated that the reactive center region of alpha 1-PI, the amino acid sequence of which is critical to recognition of and binding to target proteinases, is highly divergent within and among species. This appears to be a consequence of accelerated rates of evolution that may have been driven by positive Darwinian selection. In order to examine this and other features of alpha 1-PI evolution in more detail, we have isolated and sequenced cDNAs representing alpha 1- PI mRNAs of the mouse species Mus saxicola and Mus minutoides and have compared these with a number of other mammalian alpha 1-PI mRNAs. Relative to other mammalian mRNAs, the extent of nonsynonymous substitution is generally high throughout the alpha 1-PI mRNA molecule, indicating greater overall rates of amino acid substitution. Within and among mouse species, the 5'-half of the mRNA, but not the 3'-half, has been homogenized by concerted evolution. Finally, the reactive center is under diversifying or positive Darwinian selection in murid rodents (rats, mice) and guinea pigs yet is under purifying selection in primates and artiodactyls. The significance of these findings to alpha 1-PI function and the possible selective forces driving evolution of serpins in general are discussed.      

Mitochondrial DNA polymorphisms in subterranean mole-rats of the Spalax ehrenbergi superspecies in Israel, and its peripheral isolates

Patterns of mitochondrial DNA (mtDNA) variation were examined in 133 mole-rats constituting all four chromosomal species (2n = 52, 2n = 54, 2n = 58, and 2n = 60) of the Spalax ehrenbergi superspecies in Israel, as well as the peripheral isolates of 2n = 60. In the main range of the complex, a total of 28 mtDNA haplotypes were found in 64 mole-rats, with most haplotypes being unique to either a single chromosomal species or population. mtDNA divergence increased from low to high diploid number in a north-to-south direction in Israel. Overall levels of mtDNA diversity were unexpectedly the highest in the 2n = 60, the youngest species of the complex. The mtDNA haplotypes can be separated into two major groups, 2n = 52-54 and 2n = 58-60, and a phylogenetic analysis for each group revealed evidence of a few haplotypes not sorted by diploid number. The overall patterns of mtDNA divergence seen within and among the four chromosomal species are consistent with the parapatric mode of speciation as suggested from previous studies of allozyme and DNA hybridization. In a separate data set the patterns of mtDNA variation were examined across the main geographic range and across peripheral semi-isolates and isolates of the 2n = 60 chromosomal species. Fifteen haplotypes were found in 69 mole-rats. High levels of mtDNA diversity characterized the main range, semi-isolated, and even some desert isolated populations. The peripheral isolates contain much mtDNA diversity, including novel haplotypes.      

Sulfite inhibition of photochemical activity of intact pea leaves

Sulfite treatment of pea leaf disks in light caused a significant decrease in the relative quantum yield of photosynthetic oxygen evolution and energy storage (ES) as measured by photoacoustic (PA) spectroscopy. The inhibition was concentration dependent and was less in darkness than in light, indicating light-dependent inhibitory site(s) on the photosynthetic electron transport chain. Further, in darksulfite-treated leaves, the energy storage was more affected than the relative quantum yield of oxygen evolution, suggesting that photophosphorylation and/or cyclic electron transport around PS I are sites of sulfite action in darkness. The R_fd values, the ratio of fluorescence decrease (fd) to the steady-state fluorescence (fs), decreased significantly in leaves treated with sulfite in light but were not affected in dark-treated ones, confirming the photoacoustic observations. Similarly, the ratio of variable fluorescence (F_v) to maximum fluorescence (F_m), a measure of PS II photochemical efficiency, was affected by sulfite treatment in light and not changed by treatment in darkness. An attempt was made to explain the mechanism of sulfite action on photosynthetic electron transport in light and in darkness.Abbreviations A_PT amplitude of photothermal signal - A_ox amplitude of oxygen signal - ES energy storage - fd fluorescence decrease - fs steady-state fluorescence - F_m maximum fluorescence - F_v variable fluorescence - PA photoacoustic(s)     

Energy storage and optical cross-section of PS I in the cyanobacterium Synechococcus PCC 7002 and a psaE- mutant

In vivo electron flow in the unicellular cyanobacterium Synechococcus sp. PCC 7002 was studied by pulsed, time- resolved photoacoustics (PTRPA). Using 1-s, 2 J or 10¹³ hcm-2 pulses at 695 nm, we observed large (42 ± 2%) Photosystem I (PS I) cyclic energy storage (ES) in the period of 2 to 12 ms after excitation with wild type (WT) intact cells. This cyclic ES was insensitive to flash interval from 0.3 to 10 s and to the presence of 1 m DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea). At this low flash energy and in the absence of continuous background light (in the dark), antimycin A, carbonylcyanide-m- chlorophenylhydrazone (CCCP), 2,5-dibromo-3-methyl-6-isopropyl- p-benzoquinone (DBMIB), DCMU, 2- n-heptyl-4- hydroxyquinoline-N-oxide (HQNO), myxothiazol and N- ethylmaleimide (NEM) caused little or no inhibition of PS I cyclic electron flow. When continuous background far-red light ( > 715 nm) was added during the measurement, strong inhibition by DBMIB and NEM and less by HQNO was observed, the amplitude of which was related to both concentration and the intensity of the background light. Analysis of the data with DBMIB yields its binding constant, 1 m, and the turnover time of the system (> 20 ms). A turnover time of the uninhibited system of 2–3 ms was obtained by a pump-probe method. A dramatic lifting of the partial inhibition in the presence of far-red light was caused by antimycin A and a smaller effect by myxothiazol. The rescuing effect was assigned to a short circuiting of the electron flow about the cytochrome (cyt) b6/f system. Progressively increasing the laser pulse energy allowed us to calculate the PS I optical cross-section (54 ± 2 Å). Analysis by the sensitive method of convolutions revealed a possible energy loss on the few ms time scale by antimycin A in the dark. The analysis also revealed a similar effect or artifact in uninhibited samples using the same sample illuminated with saturating continuous light, the standard procedure in photoacoustics (PA). A psaE- mutant showed more inhibition in the dark by DBMIB and with far-red light by HQNO, but less inhibition in the far-red light by myxothiazol than the WT. Under normal growth conditions, maximum ES for the psaE- mutant (38 ± 2%) was similar to that of the WT (42 ± 2%). However, under mild heat stress, maximum ES for the psaE- mutant dropped to 26% while the WT maximum ES stayed unchanged at 41%, within batch-to-batch variation. These results would indicate that the PsaE protein is not essential for PS I cyclic electron flow under our experimental conditions but plays a stabilizing role in the PS I complex under a mild thermal stress.     

Regulation of DNaseY activity by actinin-alpha4 during apoptosis

DNaseY, a Ca(2+)- and Mg(2+)-dependent endonuclease, has been implicated in apoptotic DNA degradation; however, the molecular mechanisms controlling its involvement in this process have not been fully elucidated. We have obtained evidence from yeast two-hybrid screening and coimmunoprecipitation experiments that DNaseY interacted physically with actinin-alpha4 and this interaction significantly enhanced its endonuclease activity. Accordingly, simultaneous overexpression of both proteins in PC12 cells dramatically increased the rate of apoptosis in response to teniposide' VM26. However, overexpression of DNaseY alone neither triggered apoptosis nor facilitated cell death in response to VM26 or serum deprivation. Instead, the overexpression of DNaseY increased the production of single-strand DNA breaks and evoked a profound upregulation of DNA repair pathways. Taken together, our results point to a novel regulatory mechanism of DNaseY activity and offer an explanation for why cells must first cleave key DNA repair and replication proteins before the successful execution of apoptosis.     

Phylogenetic utility of the nuclear gene arginine decarboxylase: an example from Brassicaceae

Arginine decarboxylase (ADC) is an important enzyme in the production of putrescine and polyamines in plants. It is encoded by a single or low-copy nuclear gene that lacks introns in sequences studied to date. The rate of Adc amino acid sequence evolution is similar to that of ndhF for the angiosperm family studied. Highly conserved regions provide several target sites for PCR priming and sequencing and aid in nucleotide and amino acid sequence alignment across a range of taxonomic levels, while a variable region provides an increased number of potentially informative characters relative to ndhF for the taxa surveyed. The utility of the Adc gene in plant molecular systematic studies is demonstrated by analysis of its partial nucleotide sequences obtained from 13 representatives of Brassicaceae and 3 outgroup taxa, 2 from the mustard oil clade (order Capparales) and 1 from the related order Malvales. Two copies of the Adc gene, Adc1 and Adc2, are found in all members of the Brassicaceae studied to data except the basal genus Aethionema. The resulting Adc gene tree provides robust phylogenetic data regarding relationships within the complex mustard family, as well as independent support for proposed tribal realignments based on other molecular data sets such as those from chloroplast DNA.