Changes in thylakoid polypeptide phosphorylation during membrane biogenesis in Chlamydomonas reinhardii y-1

Thylakoid polypeptide phosphorylation has been studied in vivo and in vitro during plastid differentiation in Chlamydomonas reinhardii y-1. Pulse labeling cells at different stages of greening with [³²P]orthophosphate revealed differences in the pattern of protein phosphorylation. In the early phase of greening the 44–47 kDa reaction center II polypeptides were labeled but the 22–24 kDa polypeptides of the light-harvesting chlorophyll $\text{a}\text{b-}\text{protein}$ complex (LHC) were not. Later in the greening, coinciding with the formation of the antenna of Photosystem I and membrane stacking, the converse was found. Furthermore, the 22–24 kDa polypeptides of grana lamellae were less labeled than the same polypeptides found in the corresponding stroma lamellae. Polypeptides in the molecular mass range of 32–34 kDa were phosphorylated at all stages following the onset of greening. Dark-grown cells did not incorporate ³²P in vivo or in vitro into the polypeptides present in the residual thylakoids. Similarly, cells greened in the presence of chloramphenicol, in which the synthesis of reaction centers is inhibited, showed no light-stimulated phosphorylation in vitro. However, the residual 32–34 kDa and 44–47 kDa polypeptides found in thylakoids of these cells were phosphorylated in vivo, whereas the LHC polypeptides synthesized in the presence of chloramphenicol were not. Phosphorylation of the LHC polypeptides (22–24 kDa) in these cells occurred if new reaction center polypeptides and all antennae components were formed, following removal of the inhibitor and further incubation of the cells in the light. Phosphorylation of LHC polypeptides was not resumed if active reaction centers were formed in the absence of complete restoration of all antenna components (incubation in the dark or light with addition of cycloheximide). It is concluded that phosphorylation is correlated with the thylakoid polypeptide content and organization.     

Chick lens differentiation in vitro

If that portion of a chick embryo destined to form the eye, the lens, part of the brain and the surrounding head region be removed from the chick before the lens has begun to develop, and placed in a liquid culture medium for four days, a structure resembling the lens will form in appropriate proximity to the presumptive retina, and the cells of the lens will synthesize proteins unique to and characteristic of the lens. The time course of morphological development of such explants is here described. In vitro the lens placode dose not invaginate to form a lens vesicle, as it does in ovo. Instead placode cells elongate directly to form fibre cells. The shape of the lens formed in this aberrant manner is remarkably similar to that of normal lens. At least one, and probably all three, of the characteristic crystallins of the lens form in these aberrant lenses, the cytological and biochemical differentiation of which proceeds normally, despite failure of the normal morphogenetic activities of the organ.     

Lethality of T-2 toxin,as applied by various methods,in adultAedes aegypti (Diptera: Culicidae) mosquitoes

The lethality of T-2 toxin to adult femaleAedes aegypti mosquitoes was investigated using various methods of application: Topically, by injection, and by natural feeding. The technique of topical application was found to be the most precise, whereby an LD₅₀ of 565 ng T-2 toxin/mosquito was determined.     

Technique for Screening 2n Combinations of Nutritional Requirements

An auxanographic technique is described, which makes it possible to screen 2(n) combinations of nutrients on relatively few agar plates.     

Oculopharyngeal muscular dystrophy mutations link the RNA-binding protein HNRNPQ to autophagosome biogenesis

Autophagy is an intracellular degradative process with an important role in cellular homeostasis. Here, we show that the RNA binding protein (RBP), heterogeneous nuclear ribonucleoprotein Q (HNRNPQ)/SYNCRIP is required to stimulate early events in autophagosome biogenesis, in particular the induction of VPS34 kinase by ULK1-mediated beclin 1 phosphorylation. The RBPs HNRNPQ and poly(A) binding protein nuclear 1 (PABPN1) form a regulatory network that controls the turnover of distinct autophagy-related (ATG) proteins. We also show that oculopharyngeal muscular dystrophy (OPMD) mutations engender a switch from autophagosome stimulation to autophagosome inhibition by impairing PABPN1 and HNRNPQ control of the level of ULK1. The overexpression of HNRNPQ in OPMD patient-derived cells rescues the defective autophagy in these cells. Our data reveal a regulatory mechanism of autophagy induction that is compromised by PABPN1 disease mutations, and may thus further contribute to their deleterious effects.