Primary Succession on a Hawaiian Dryland Chronosequence

We used measurements from airborne imaging spectroscopy and LiDAR to quantify the biophysical structure and composition of vegetation on a dryland substrate age gradient in Hawaii. Both vertical stature and species composition changed during primary succession, and reveal a progressive increase in vertical stature on younger substrates followed by a collapse on Pleistocene-aged flows. Tall-stature Metrosideros polymorpha woodlands dominated on the youngest substrates (hundreds of years), and were replaced by the tall-stature endemic tree species Myoporum sandwicense and Sophora chrysophylla on intermediate-aged flows (thousands of years). The oldest substrates (tens of thousands of years) were dominated by the short-stature native shrub Dodonaea viscosa and endemic grass Eragrostis atropioides. We excavated 18 macroscopic charcoal fragments from Pleistocene-aged substrates. Mean radiocarbon age was 2,002 years and ranged from < 200 to 7,730. Genus identities from four fragments indicate that Osteomeles spp. or M. polymorpha once occupied the Pleistocene-aged substrates, but neither of these species is found there today. These findings indicate the existence of fires before humans are known to have occupied the Hawaiian archipelago, and demonstrate that a collapse in vertical stature is prevalent on the oldest substrates. This work contributes to our understanding of prehistoric fires in shaping the trajectory of primary succession in Hawaiian drylands.     

Isolation of a <Emphasis Type="Italic">Latimeria menadoensis</Emphasis><Emphasis Type="Italic">heat shock protein 70</Emphasis> (<Emphasis Type="Italic">Lmhsp70</Emphasis>) that has all the features of an inducible gene and encodes a functional molecular chaperone

Molecular chaperones facilitate the correct folding of other proteins, and heat shock proteins form one of the major classes of molecular chaperones. Heat shock protein 70 (Hsp70) has been extensively studied, and shown to be critically important for cellular protein homeostasis in almost all prokaryotic and eukaryotic systems studied to date. Since there have been very limited studies conducted on coelacanth chaperones, the main objective of this study was to genetically and biochemically characterize a coelacanth Hsp70. We have successfully isolated an Indonesian coelacanth (L. menadoensis) hsp70 gene, Lmhsp70, and found that it contained an intronless coding region and a potential upstream regulatory region. Lmhsp70 encoded a typical Hsp70 based on conserved structural and functional features, and the predicted upstream regulatory region was found to contain six potential promoter elements, and three potential heat shock elements (HSEs). The intronless nature of the coding region and the presence of HSEs suggested that Lmhsp70 was stress-inducible. Phylogenetic analyses provided further evidence that Lmhsp70 was probably inducible, and that it branched as a clade intermediate between bony fish and tetrapods. Recombinant LmHsp70 was successfully overproduced, purified and found to be functional using ATPase activity assays. Taken together, these data provide evidence for the first time that the coelacanth encodes a functional molecular chaperone system. K. W. Modisakeng and M. Jiwaji contributed equally to this study.     

The evolution of cytoplasmic incompatibility types: integrating segregation, inbreeding and outbreeding

Cytoplasmic incompatibility (CI) is a reproductive incompatibility induced by maternally transmitted bacteria of the genera Wolbachia and Cardinium. In the simplest form of CI, offspring from infected males and uninfected females suffer from increased mortality. However, it has been noted that crosses between males and females carrying different strains of infection are often also incompatible. The evolutionary processes leading to the emergence of new CI-compatibility types are still not resolved. Here, we develop a model that extends previous theoretical approaches by including segregation of bacterial strains during transmission as well as a continuum of breeding systems ranging from inbreeding (complete sib mating) to outbreeding (complete sib-mating avoidance). Our results demonstrate that (1) with segregation of strains, evolution is unlikely to lead to new CI types that co-occur as a double infection with the preexisting one, (2) inbreeding substantially hampers the evolution of new CI types, and (3) outbreeding facilitates the evolution of new CI types. Our model also provides a hypothesis on the evolutionary origin of CI.     

Targeted transposition by the V(D)J recombinase

Cleavage by the V(D)J recombinase at a pair of recombination signal sequences creates two coding ends and two signal ends. The RAG proteins can integrate these signal ends, without sequence specificity, into an unrelated target DNA molecule. Here we demonstrate that such transposition events are greatly stimulated by--and specifically targeted to--hairpins and other distorted DNA structures. The mechanism of target selection by the RAG proteins thus appears to involve recognition of distorted DNA. These data also suggest a novel mechanism for the formation of alternative recombination products termed hybrid joints, in which a signal end is joined to a hairpin coding end. We suggest that hybrid joints may arise by transposition in vivo and propose a new model to account for some recurrent chromosome translocations found in human lymphomas. According to this model, transposition can join antigen receptor loci to partner sites that lack recombination signal sequence elements but bear particular structural features. The RAG proteins are capable of mediating all necessary breakage and joining events on both partner chromosomes; thus, the V(D)J recombinase may be far more culpable for oncogenic translocations than has been suspected.     

Seasonal changes in adiposity: the roles of the photoperiod,melatonin and other hormones,and sympathetic nervous system

It appears advantageous for many non-human animals to store energy body fat extensively and efficiently because their food supply is more labile and less abundant than in their human counterparts. The level of adiposity in many of these species often shows predictable increases and decreases with changes in the season. These cyclic changes in seasonal adiposity in some species are triggered by changes in the photoperiod that are faithfully transduced into a biochemical signal through the nightly secretion of melatonin (MEL) via the pineal gland. Here, we focus primarily on the findings from the most commonly studied species showing seasonal changes in adiposity-Siberian and Syrian hamsters. The data to date are not compelling for a direct effect of MEL on white adipose tissue (WAT) and brown adipose tissue (BAT) despite some recent data to the contrary. Thus far, none of the possible hormonal intermediaries for the effects of MEL on seasonal adiposity appear likely as a mechanism by which MEL affects the photoperiodic control of body fat levels indirectly. We also provide evidence pointing toward the sympathetic nervous system as a likely mediator of the effects of MEL on short day-induced body fat decreases in Siberian hamsters through increases in sympathetic drive on WAT and BAT. We speculate that decreases in the SNS drive to these tissues may underlie the photoperiod-induced seasonal increases in body fat of species such as Syrian hamsters. Clearly, we need to deepen our understanding of seasonal adiposity, although, to our knowledge, this is the only form of environmentally induced changes in body fat where the key elements of its external trigger have been identified and can be traced to and through their transduction into a physiological stimulus that ultimately affects identified responses of white adipocyte physiology and cellularity. Finally, the comparative physiological approach to the study of seasonal adiposity seems likely to continue to yield significant insights into the mechanisms underlying this phenomenon and for understanding obesity and its reversal in general.     

Anaerobic Degradation of Normal- and Branched-Chain Fatty Acids with Four or More Carbons to Methane by a Syntrophic Methanogenic Triculture

Syntrophic degradation of normal- and branched-chain fatty acids with 4 to 9 carbons was investigated with a mesophilic syntrophic isobutyrate-butyrate-degrading triculture consisting of the non-spore-forming, syntrophic, fatty acid-degrading, gram-positive rod-shaped strain IB, Methanobacterium formicicum T1N, and Methanosarcina mazei T18. This triculture converted butyrate and isobutyrate to methane and converted valerate and 2-methylbutyrate to propionate and methane. This triculture also degraded caproate, 4-methylvalerate, heptanoate, 2-methylhexanoate, caprylate, and pelargoate. During the syntrophic conversion of isobutyrate and butyrate, a reversible isomerization between butyrate and isobutyrate occurred; isobutyrate and butyrate were isomerized to the other isomeric form to reach nearly equal concentrations and then their concentrations decreased at the same rates. Butyrate was an intermediate of syntrophic isobutyrate degradation. When butyrate was degraded in the presence of propionate, 2-methylbutyrate was synthesized from propionate and isobutyrate formed from butyrate. During the syntrophic degradation of valerate, isobutyrate, butyrate, and 2-methylbutyrate were formed and then degraded. During syntrophic degradation of 2-methylbutyrate, isobutyrate and butyrate were formed and then degraded.     

Music and dance as a coalition signaling system

Evidence suggests that humans might have neurological specializations for music processing, but a compelling adaptationist account of music and dance is lacking. The sexual selection hypothesis cannot easily account for the widespread performance of music and dance in groups (especially synchronized performances), and the social bonding hypothesis has severe theoretical difficulties. Humans are unique among the primates in their ability to form cooperative alliances between groups in the absence of consanguineal ties. We propose that this unique form of social organization is predicated on music and dance. Music and dance may have evolved as a coalition signaling system that could, among other things, credibly communicate coalition quality, thus permitting meaningful cooperative relationships between groups. This capability may have evolved from coordinated territorial defense signals that are common in many social species, including chimpanzees. We present a study in which manipulation of music synchrony significantly altered subjects’ perceptions of music quality, and in which subjects’ perceptions of music quality were correlated with their perceptions of coalition quality, supporting our hypothesis. Our hypothesis also has implications for the evolution of psychological mechanisms underlying cultural production in other domains such as food preparation, clothing and body decoration, storytelling and ritual, and tools and other artifacts. Edward Hagen is a research scientist at the Institute for Theoretical Biology, Humboldt University, Berlin. Gregory Bryant is a doctoral candidate in the Department of Psychology, University of California, Santa Cruz.     

Alterations of Red Cell Membrane Properties in Nneuroacanthocytosis

Neuroacanthocytosis (NA) refers to a group of heterogenous, rare genetic disorders, namely chorea acanthocytosis (ChAc), McLeod syndrome (MLS), Huntington’s disease-like 2 (HDL2) and pantothenate kinase associated neurodegeneration (PKAN), that mainly affect the basal ganglia and are associated with similar neurological symptoms. PKAN is also assigned to a group of rare neurodegenerative diseases, known as NBIA (neurodegeneration with brain iron accumulation), associated with iron accumulation in the basal ganglia and progressive movement disorder. Acanthocytosis, the occurrence of misshaped erythrocytes with thorny protrusions, is frequently observed in ChAc and MLS patients but less prevalent in PKAN (about 10%) and HDL2 patients. The pathological factors that lead to the formation of the acanthocytic red blood cell shape are currently unknown. The aim of this study was to determine whether NA/NBIA acanthocytes differ in their functionality from normal erythrocytes. Several flow-cytometry-based assays were applied to test the physiological responses of the plasma membrane, namely drug-induced endocytosis, phosphatidylserine exposure and calcium uptake upon treatment with lysophosphatidic acid. ChAc red cell samples clearly showed a reduced response in drug-induced endovesiculation, lysophosphatidic acid-induced phosphatidylserine exposure, and calcium uptake. Impaired responses were also observed in acanthocyte-positive NBIA (PKAN) red cells but not in patient cells without shape abnormalities. These data suggest an “acanthocytic state” of the red cell where alterations in functional and interdependent membrane properties arise together with an acanthocytic cell shape. Further elucidation of the aberrant molecular mechanisms that cause this acanthocytic state may possibly help to evaluate the pathological pathways leading to neurodegeneration.