Phenotype of a mechanosensitive channel mutant, mid-1, in a filamentous fungus, Neurospora crassa.

In the yeast Saccharomyces cerevisiae, the MID1 (mating-induced death) gene encodes a stretch-activated channel which is required for successful mating; the mutant phenotype is rescued by elevated extracellular calcium. Homologs of the MID1 gene are found in fungi that are morphologically complex compared to yeast, both Basidiomycetes and Ascomycetes. We explored the phenotype of a mid-1 knockout mutant in the filamentous ascomycete Neurospora crassa.

Role of a mitogen-activated protein kinase cascade in ion flux-mediated turgor regulation in fungi.

Fungi normally maintain a high internal hydrostatic pressure (turgor) of about 500 kPa. In response to hyperosmotic shock, there are immediate electrical changes: a transient depolarization (1 to 2 min) followed by a sustained hyperpolarization (5 to 10 min) prior to turgor recovery (10 to 60 min). Using ion-selective vibrating probes, we established that the transient depolarization is due to Ca(2+) influx and the sustained hyperpolarization is due to H(+) efflux by activation of the plasma membrane H(+)-ATPase.

Functional identification of the glycerol transport activity of Chlamydomonas reinhardtii CrMIP1.

By searching a Chlamydomonas expressed sequence tag database and by comparing the retrieved data with homologous sequences from a DNA database, we identified an expressed Chlamydomonas reinhardtii putative major intrinsic protein (MIP) gene. The nucleotide sequence, consisting of 1,631 bp, contains an open reading frame coding for a 300-amino-acid protein named CrMIP1. It possesses conserved NPA motifs, but is not highly homologous to known aquaporins.

Identification of a mitochondrial nucleoside diphosphate kinase from the green alga Dunaliella tertiolecta.

We isolated a full-length cDNA encoding a nucleoside diphosphate (NDP) kinase from a Dunaliella tertiolecta cDNA library by homology cloning and rapid amplification of cDNA ends-PCR. The cDNA sequence, consisting of 840 bp, contained an open reading frame coding for a 221-amino acid protein. The predicted 24-kDa protein was named DtNDK1.