PII signal transduction protein in Chlamydomonas reinhardtii: localization and expression pattern.

Although PII signal transduction proteins have been described in bacteria, archaea and higher plants, no PII homolog has so far been characterized in green algae. In the unicellular green alga Chlamydomonas reinhardtii, the PII protein is encoded by a single nuclear gene CrGLB1. The C.

Regulation by light of ammonium transport systems in Chlamydomonas reinhardtii.

The unicellular green alga Chlamydomonas reinhardtii is able to take up methylammonium/ammonium from the medium at different stages of its sexual life cycle. Vegetative cells and pre-gametes mostly used a low-affinity system (LATS) component, but gametes obtained after light treatment of N-deprived pre-gametes expressed both LATS and high-affinity system (HATS) components for the uptake of methylammonium/ammonium. The activity of the LATS component was stimulated by light in only 5 min in a process independent of protein synthesis.

Chemotaxis to ammonium/methylammonium in Chlamydomonas reinhardtii: the role of transport systems for ammonium/methylammonium.

Ammonium is the preferred nitrogen source and chemoattractant for the unicellular green alga Chlamydomonas reinhardtii. Here we describe that chemotaxis to methylammonium, a non-metabolizable analogue to ammonium, that occurs only in vegetative cells and pregametes but not in gametes. A new methylammonium-resistant mutant, hat1 that was generated by insertional mutagenesis, has been isolated and found to be affected at multiple loci.

Phototropin plays a crucial role in controlling changes in chemotaxis during the initial phase of the sexual life cycle in Chlamydomonas.

During sexual differentiation, Chlamydomonas reinhardtii changes its chemotactic behavior in response to ammonium. Just like gamete formation, the change in chemotaxis mode is controlled by the sequential action of two environmental cues, removal of ammonium or nitrate from the medium and light. Thus, vegetative cells and mating incompetent pre-gametes, the latter being generated by nitrogen starvation in the dark, exhibit chemotaxis towards ammonium.

[Functional specialization of the nuclei in tip-growing coenocytic algae Vaucheria sessilis].

The availability of numerous nuclei in coenocytic thalli creates a problem of their activity and division cycle coordination. An apparent random distribution of nuclei in tip-growing cells is regulated by some principles associated with physiological compartmentalization in the absence of true septae. In vegetative thallome of Vaucheria sessilis the nuclei are distributed equally in proximal parts, to be accumulated in a high density cluster in the apical zone.

Chemotactic behavior of Chlamydomonas reinhardtii is altered during gametogenesis.

Chemotactic behavior of Chlamydomonas reinhardtii is altered during the sexual life cycle. Unlike vegetative cells and noncompetent pregametes, mature gametes did not show chemotaxis to ammonium. Loss of chemotaxis to ammonium in mating-competent cells is controlled by gamete-specific genes that are common for both mating-type gametes.

Isolation and characterisation of chemotactic mutants of Chlamydomonas reinhardtii obtained by insertional mutagenesis.

The swimming behaviour of the green flagellated protist Chlamydomonas reinhardtii is influenced by several different external stimuli including light and chemical attractants. Common components are involved in both the photo- and chemo-sensory transduction pathways, although the nature and organisation of these pathways are poorly understood. To learn more about the mechanism of chemotaxis in Chlamydomonas, we have generated nonchemotactic strains by insertional mutagenesis.

A case of abnormal size in eggs and larvae of the Taiga tick, Ixodes persulcatus (Acari: Ixodidae).

Egg batches laid by females of Ixodes persulcatus (maintained under a photoperiod of L:D 20:4 before feeding) contained eggs of two sizes: numerous normal eggs of 0.578 x 0.421 mm and some giant eggs of 0.