Conjugation Rescue of Exocytosis Mutants in Tetrahymena thermophila Indicates the Presence of Functional Intermediates in the Regulated Secretory Pathway

ABSTRACT. Tetrahymena thermophila possesses a regulated secretory pathway in which mucin proteins are stored in dense-core granules, called mucocysts. Exocytosis-defective mutants exist that fail to secrete mucin in response to secretagogues. Four of the mutants (SB281, SB283, SB285 and SB715) appear to be blocked at different steps of the regulated secretory pathway. SB281 and SB285 accumulate mucin proteins in heterogeneous cytoplasmic organelles which have not yet been identified; SB283 makes mucocyst-like structures but they contain no immunologically identifiable 80-kDa or 50-kDa mucin proteins; and SB715 has more than normal amounts of immature and undocked mucocysts. The organelles that accumulate in exocytosis-defective mutants could be either normal intermediates in the biosynthetic pathway or aberrant structures that form as a result of the mutations. We have used conjugation rescue to analyze steps in the biogenesis of exocytosis-competent mucocysts and to identify functional intermediates. The cytoplasmic organelles that accumulate in SB281 appear to be unidentified biosynthetic intermediates, and the defect is in a cytosolic protein essential for mucocyst maturation. The organelles which accumulate in the other mutants are likely biosynthetic, but their mutations are in proteins which are labile or not free to diffuse into the mutant conjugant.     

Ants and the enigmatic Namibian fairy circles – cause and effect?

1. Parts of the Namibian landscape show extensive surface perturbation in the form of long‐lived, yet dynamic ‘fairy circles'. While exerting profound ecological effects on 7.3% of the land surface, the origin and nature of these large bare discs embedded in an arid grassland matrix remains unresolved. 2. We found no evidence to support the current hypothesis of a termite origin for fairy circles but instead observed a strong spatial association between fairy circles and large nests of the ant Black pugnacious ant Anoplolepis steingroeveri Forel, with much higher ant abundances on the circles compared with the matrix. 3. Aggression trials showed that different colonies of A. steingroeveri were located on different circles, and that the species was polydomous. 4. Fairy circles and Pogonomyrmex ant nests both have a bare disc surrounding the nest, are overdispersed (evenly spaced), and are associated with elevated soil moisture. Fairy circle soils exhibited a five‐fold increase in soil moisture when compared with the matrix. 5. Senescent Stipagrostis obtusa (Delile) Nees seedlings were only observed on the circles and not in the matrix, and were found to have a reduction in both root length and number of roots. 6. Anoplolepis steingroeveri excavated the root system of both S. obtusa seedlings on the disc and Stipagrostis ciliata (Desf.) de Winter grasses on the perimeter of the circles, where they tended honeydew‐secreting Meenoplidae bugs that fed on grass roots and culms. The bugs occurred almost exclusively on grasses associated with the circles. This ant–bug interaction is a possible mechanism for the observed reduction in root length and number of senescent grass seedlings on the circles.     

Using Advancements in Cable-Trapping to Overcome Barriers to Furbearer Management in the United States

ABSTRACT Harvest of furbearers through trapping has been challenged by anti-trapping organizations for centuries, with organizational goals often including prohibition of all forms of trapping. Challenges to trapping may also include dissention among state wildlife agencies, pro-hunting organizations, and pro-trapping organizations. Despite recent efforts by anti-trapping organizations and occasional dissention among consumptive-use groups, national trends in snaring regulations included less restrictive regulations through time. This positive trend may offer opportunities for state wildlife agencies and pro-trapping organizations to enhance the public image of trapping, increase recruitment of trappers, and reverse the increasing trend of wildlife damage and associated costs. We offer support and suggestions to state wildlife agencies and pro-trapping organizations to help achieve these goals, with their partnership likely having a synergistic effect. Although we attempt to illuminate approaches for increasing support for trapping within the constraints of the cultural norms of the United States, we hope our approaches are useful to and promote dialogue in other jurisdictions experiencing similar problems.