<Emphasis Type="Italic">Arabidopsis tanmei/emb2757</Emphasis> embryo mutant is defective for in vitro plant morphogenesis

A mutation in the Arabidopsis TANMEI/EMB2757 (TAN) gene with an embryo defective phenotype was analysed for its effect on the morphogenic potential of somatic tissue cultured under in vitro conditions. The capacity for in vitro morphogenesis was evaluated using cultures of immature zygotic embryos, and seedling explants of the tan mutant and the parental Col-0 genotype. The explants were cultured on media supplemented with different plant growth regulators, and the capacity for two alternative pathways of morphogenesis, somatic embryogenesis (SE) and shoot organogenesis, was evaluated. Reporter genes (GUS, GFP) were used to monitor auxin and LEC2 and FUS3 gene activity in the tan explants. Moreover, the expression pattern of the TAN gene was analyzed during SE and in callus tissue of Col-0. It was indicated that the tan mutation resulted in a total lost of embryogenic and organogenic capacity of cultured tissues, suggesting the involvement of the TAN gene in basic cellular processes related to cell growth and differentiation. However, differential expression of the TAN gene during SE, and its increased activity at advanced stages of embryogenesis, implicate a specific role for the gene in the development of somatic embryos.     

Changes in patterns of ADP-ribosylated proteins during differentiation of Streptomyces coelicolor A3(2) and its development mutants.

Mutants resistant to 3-aminobenzamide, a known inhibitor of ADP-ribosyltransferase, were obtained from Streptomyces coelicolor A3(2). One (strain 27) was analyzed in detail. Mutant 27 had a reduced ADP-ribosyl-transferase activity, exhibited substantial changes from the wild type in ADP-ribosylated protein profile during cell aging, and was defective in producing aerial mycelium and antibiotics. A 92-kDa ADP-ribosylated protein disappeared at the onset of differentiation in the parent strain but was present in mutant 27. Four ADP-ribosylated proteins (39, 41, 43, and 46 kDa) appeared at the onset of differentiation in the parent strain but were missing in mutant 27. Failure to ADP-ribosylate these four proteins was detected when the parent strain was grown in the presence of subinhibitory amounts of 3-aminobenzamide. Genetic analysis showed that the mutation, named brgA, conferring resistance to 3-aminobenzamide, cosegregated with the altered phenotypes (i.e., defects in ADP-ribosylation and aerial mycelium formation) and was mapped to a new locus near uraA. The brgA mutants were nonconditionally deficient in producing aerial mycelium and antibiotics, as determined by using various media, and had a morphological and physiological phenotype quite different from that of a bldG mutant carrying a mutation which was previously mapped near uraA. Among the known bld mutants, bldA, bldD, and bldG mutants exhibited a ADP-ribosylated protein profile similar to that of the wild type, while like mutant 27, bldB, bldC, and bldH mutants failed to ADP-ribosylate certain proteins.     

spe-29 encodes a small predicted membrane protein required for the initiation of sperm activation in Caenorhabditis elegans

Caenorhabditis elegans spermatids complete a dramatic morphogenesis to crawling spermatozoa in the absence of an actin- or tubulin-based cytoskeleton and without synthesizing new gene products. Mutations in three genes (spe-8, spe-12, and spe-27) prevent the initiation of this morphogenesis, termed activation. Males with mutations in any of these genes are fertile. By contrast, mutant hermaphrodites are self-sterile when unmated due to a failure in spermatid activation. Intriguingly, mutant hermaphrodites form functional spermatozoa and become self-fertile upon mating, suggesting that spermatids can be activated by male seminal fluid. Here we describe a mutation in a fourth gene, spe-29, which mimics the phenotype of spe-8, spe-12, and spe-27 mutants. spe-29 sperm are defective in the initiation of hermaphrodite sperm activation, yet they maintain the ability to complete the morphogenetic rearrangements that follow. Mutant alleles of spe-12, spe-27, and spe-29 exhibit genetic interactions that suggest that the wild-type products of these genes function in a common signaling pathway to initiate sperm activation. We have identified the spe-29 gene, which is expressed specifically in the sperm-producing germ line and is predicted to encode a small, novel transmembrane protein.     

Proteomics analysis of global regulatory cascades involved in clavulanic acid production and morphological development in <Emphasis Type="Italic">Streptomyces clavuligerus</Emphasis>

The genus Streptomyces comprises bacteria that undergo a complex developmental life cycle and produce many metabolites of importance to industry and medicine. Streptomyces clavuligerus produces the β-lactamase inhibitor clavulanic acid, which is used in combination with β-lactam antibiotics to treat certain β-lactam resistant bacterial infections. Many aspects of how clavulanic acid production is globally regulated in S. clavuligerus still remains unknown. We conducted comparative proteomics analysis using the wild type strain of S. clavuligerus and two mutants (ΔbldA and ΔbldG), which are defective in global regulators and vary in their ability to produce clavulanic acid. Approximately 33.5 % of the predicted S. clavuligerus proteome was detected and 192 known or putative regulatory proteins showed statistically differential expression levels in pairwise comparisons. Interestingly, the expression of many proteins whose corresponding genes contain TTA codons (predicted to require the bldA tRNA for translation) was unaffected in the bldA mutant.