Digest: Habitat and competition drive diversification in Gondwanan fish

Why do some clades diversify more than others? And what are the roles of abiotic and biotic factors in driving such unequal diversification? To explore this, Burns et al. (2024) investigate variation in body morphology in a group of freshwater fish, Characiformes, across South America and Africa. They find that habitat features such as slope, elevation, and flow rates have played a major role in the diversification of morphological variation in the Characiformes. The Neotropical lineages residing in significantly more diverse slope and elevation habitats were found to display more body shape diversity than African lineages. The authors also report that competition might have limited the morphological variation in African Characiformes compared to the Neotropical lineages. This study highlights the importance of exploring both abiotic and biotic factors when examining diversification.

<b>New distribution records of Elegant Water Shrew <I>Nectogale elegans</I> Milne-Edwards, 1870 (Mammalia: Eulipotyphla: Soricidae) from the western Himalaya, Uttarakhand, India</b>

Of the 13 known species of water shrews in the world, two water shrews are known from India, the Elegant Water Shrew Nectogale elegans and Himalayan Water Shrew Chimmarogale himalayica.  Of these, the Elegant Water Shrew was earlier reported only from streams of north Sikkim, and Arunachal Pradesh, India.  During the period 2014–2016, the Elegant Water Shrews were sighted at three different locations in Uttarakhand State in the western Himalayan region.  The present records are evidence for the broader range of distribution of Nectogale elegans in India indicating that the species is more widely distributed than previously thought.  We present the details of sightings, habitats and behavior of shrews that were recorded during our study on impact of climate change on the aquatic ecosystem of the Himalaya.

C. elegans EGL-9 and mammalian homologs define a family of dioxygenases that regulate HIF by prolyl hydroxylation

HIF is a transcriptional complex that plays a central role in mammalian oxygen homeostasis. Recent studies have defined posttranslational modification by prolyl hydroxylation as a key regulatory event that targets HIF-alpha subunits for proteasomal destruction via the von Hippel-Lindau ubiquitylation complex. Here, we define a conserved HIF-VHL-prolyl hydroxylase pathway in C. elegans, and use a genetic approach to identify EGL-9 as a dioxygenase that regulates HIF by prolyl hydroxylation. In mammalian cells, we show that the HIF-prolyl hydroxylases are represented by a series of isoforms bearing a conserved 2-histidine-1-carboxylate iron coordination motif at the catalytic site. Direct modulation of recombinant enzyme activity by graded hypoxia, iron chelation, and cobaltous ions mirrors the characteristics of HIF induction in vivo, fulfilling requirements for these enzymes being oxygen sensors that regulate HIF.

Mutagenesis studies on the iron binding ligands of clavaminic acid synthase

Mutagenesis studies on conserved histidine residues identified as possible metal binding ligands in clavaminic acid synthase isozyme 2 were consistent with His-145 and His-280 acting as iron ligands, in support of crystallographic and previous mutagenesis studies. Mutagenesis of the four cysteines and a glutamine residue, conserved in both clavaminic acid synthase isozymes 1 and 2, demonstrated that none of these residues is essential for activity.

PaaSiCats: novel polyamino acid catalysts

The abilities of five polyamino acids (Paa's) to catalyse the asymmetric epoxidation of enones 1-7 under three sets of reaction conditions were compared: polyneo-pentylglycine and polyleucine showed distinct advantages in most circumstances. All five polymers were adsorbed onto silica and from this further study, immobilised polyneo-pentylglycine (PLNSi) and polyleucine (PLLSi) were shown to be the catalysts of choice for the asymmetric epoxidation of less-reactive alpha,beta-unsaturated ketones.