The temperature–size rule in a rotifer is determined by the mother and at the egg stage

In most ectotherms, compared with development at low temperatures, development at high temperatures results in the acceleration of maturation, which in turn results in a smaller size (temperature–size rule, TSR). It is not known at which developmental stages this thermal response is determined. We exposed different life stages of the rotifer Lecane inermis to 15, 20, or 25 °C to determine whether the TSR in the F1 generation is governed by the thermal conditions experienced by the mothers (F0 generation) during their development, during egg production, or during the development of the eggs or hatchlings. We found that the adult size was affected by the thermal conditions experienced by the mothers and embryos, but not by the conditions during post-hatching growth. We suggest that the thermal plasticity producing the TSR in rotifers may reflect the joint impacts of a maternal effect and a direct effect of the environment during egg development. The two-point control of the TSR resembles the thermal determination of other biological phenomena, similar to the thermally determined sex determination in ectotherms. Our results contribute not only to better understanding the proximate mechanisms of TSR, but also to comprehending the general biological mechanisms of response to temperature, which is one of the most important ecological factors.     

Structural studies of the C‐terminal 19‐peptide of serum amyloid A and its Pro→Ala variants interacting with human cystatin C

Serum amyloid A (SAA) is a multifunctional acute‐phase protein whose concentration in serum increases markedly following a number of chronic inflammatory and neoplastic diseases. Prolonged high SAA level may give rise to reactive systemic amyloid A (AA) amyloidosis, where the N‐terminal segment of SAA is deposited as amyloid fibrils. Besides, recently, well‐documented association of SAA with high‐density lipoprotein or glycosaminoglycans, in particular heparin/heparin sulfate (HS), and specific interaction between SAA and human cystatin C (hCC), the ubiquitous inhibitor of cysteine proteases, was proved. Using a combination of selective proteolytic excision and high‐resolution mass spectrometry, a hCC binding site in the SAA sequence was determined as SAA(86–104). The role of this SAA C‐terminal fragment as a ligand‐binding locus is still not clear. It was postulated important in native SAA folding and in pathogenesis of AA amyloidosis. In the search of conformational details of this SAA fragment, we did its structure and affinity studies, including its selected double/triple Pro→Ala variants. Our results clearly show that the SAA(86–104) 19‐peptide has rather unordered structure with bends in its C‐terminal part, which is consistent with the previous results relating to the whole protein. The results of affinity chromatography, fluorescent ELISA‐like test, CD and NMR studies point to an importance of proline residues on structure of SAA(86–104). Conformational details of SAA fragment, responsible for hCC binding, may help to understand the objective of hCC–SAA complex formation and its importance for pathogenesis of reactive amyloid A amyloidosis. Copyright © 2015 John Wiley & Sons, Ltd.     

A Metalloprotease Secreted by the Type II Secretion System Links Vibrio cholerae with Collagen

Vibrio cholerae is autochthonous to various aquatic niches and is the etiological agent of the life-threatening diarrheal disease cholera. The persistence of V. cholerae in natural habitats is a crucial factor in the epidemiology of cholera. In contrast to the well-studied V. cholerae-chitin connection, scarce information is available about the factors employed by the bacteria for the interaction with collagens. Collagens might serve as biologically relevant substrates, because they are the most abundant protein constituents of metazoan tissues and V. cholerae has been identified in association with invertebrate and vertebrate marine animals, as well as in a benthic zone of the ocean where organic matter, including collagens, accumulates. Here, we describe the characterization of the V. cholerae putative collagenase, VchC, encoded by open reading frame VC1650 and belonging to the subfamily M9A peptidases. Our studies demonstrate that VchC is an extracellular collagenase degrading native type I collagen of fish and mammalian origin. Alteration of the predicted catalytic residues coordinating zinc ions completely abolished the protein enzymatic activity but did not affect the translocation of the protease by the type II secretion pathway into the extracellular milieu. We also show that the protease undergoes a maturation process with the aid of a secreted factor(s). Finally, we propose that V. cholerae is a collagenovorous bacterium, as it is able to utilize collagen as a sole nutrient source. This study initiates new lines of investigations aiming to uncover the structural and functional components of the V. cholerae collagen utilization program.     

Congruence and conflict: case studies of morphotaxonomy versus rDNA gene tree phylogeny among articulate brachiopods (Brachiopoda: Rhynchonelliformea), with description of a new genus

We present five case studies among articulate (rhynchonelliform) brachiopods, i.e. of Rhynchonellida, Cancellothyridoidea, Terebratuloidea, Dyscolioidea, Laqueoidea, and various terebratulids with modified long‐loops, in an attempt to illustrate and better understand congruence and conflict between morpho‐classification and rDNA‐based molecular clade structure, having been prompted to address these issues by difficulties encountered when describing the newly collected brachiopod, E biscothyris bellonensis gen. et sp. nov. The five studies reveal dramatic conflict in the Rhynchonellida and Terebratuloidea/Dyscolioidea, good congruence in the Cancellothyridoidea and Laqueoidea, and fair congruence (albeit with weak phylogenetic signal) in the long‐looped terebratulids. We suggest that the leading cause of the observed conflict lies in the use of inadequately specific morphological characters and morpho‐classification. Phylogenetic systematic (cladistic) analyses of Rhynchonellida also conflict markedly with the rDNA gene tree, leading us to recognize that such analyses are not only conceptually circular (using morphological characters to assess a morphological classification) but also to propose that they are biased by the act of classification that necessarily precedes the identification of putatively homologous characters; when the prior classification does not reflect evolutionary history, phylogenetic analysis will do likewise. In addition, we propose that the brachiopod community has overlooked the significance of two sources of morphological homoplasy affecting brachiopod systematics: (1) the loss of co‐adapted genomic complexes caused by mass extinctions at the end of the Permian; and (2) the pervasive consequences of developmental integration and constraint resulting from the integrated roles of the outer mantle epithelium in shell deposition and growth that underly the determination of form and the shell‐based classification. © 2015 The Linnean Society of London