Different Expression Patterns of the Promoters of the NgrolB and NgrolC Genes during the Development of Tobacco Genetic Tumors

Hybrids (F1) between Nicotiana glauca and N. langsdorffii areprone to develop tumorous tissues on normaltype F1 tissues,namely, genetic tumors. To investigate the patterns of expressionof Ngrol genes during the development of genetic tumors, weperformed an analysis of transgenic genetic tumors that harboredthe promoters of the NgrolB and NgrolC genes fused to a reportergene for rß-glucuronidase (GUS) using a tumorization-redifferentiationsystem derived from F1 plants in vitro. Histochemical analysis of the expression of NgrolB-GUS in normal-typeF1 transgenic plants revealed GUS activity in meristematic zones,while in NgrolC-GUS transformed plants the activity was detectedmainly in the vascular systems of various organs. Tumorous tissues,which arose spontaneously as a consequence of aging or wereinduced by cutting, showed high levels of GUS expression underthe control of promoters of both the NgrolB and the NgrolC gene.Time course analysis during tumorization that followed cuttingof leaves of normal-type F1 plants showed clearly that NgrolB-GUSwas expressed in all dividing cells in the cut region after3 days. By contrast, the expression of NgrolC-GUS was detectedin organized tissues, such as procambium in teratomatous tumors,7–10 days after cutting treatment. During redifferentiationfrom genetic tumors to normal-type plants, the expression ofGUS under control of both Ngrol promoters decreased and expressionresembled that in normal-type tissues. These results suggestthe possibility that the Ngrol genes might be involved in formationof genetic tumors and, moreover, that the expression of NgrolBmight be linked to mitosis and while that of NgrolC might berelated to differentiation of tissues, such as the vascularsystem, in F1 plants. (Received January 19, 1996; Accepted March 24, 1996)     

Molecular Cloning and Characterization of a cDNA Clone That Encodes a Cdc2 Homolog from Nicotiana tabacum

We have isolated a cDNA clone (cdc2Nt1) that encodes a homologof p34^cdc2/CDC28 kinase from tobacco (Nicotiana tabacum). Thecdc2Ntl protein showed extensive similarity to other homologsof Cdc2 from plants. Complementation studies showed that thecdc2Ntl gene was able to overcome cell cycle arrest at boththe G1/S and the G2/M transitions of cdc28^ts mutants of buddingyeast, demonstrating that the cdc2Ntl protein was able to replacethe Cdc28 kinase at both the G1/S and the G2/M transitions.Analysis of gene expression demonstrated that the cdc2Ntl genewas transcribed constitutively throughout the cell cycle butthat it was preferentially expressed in actively dividing tobaccoBY-2 cells. (Received July 13, 1995; Accepted February 15, 1996)     

Catabolite repression of hydrolases in Aspergillus niger

Applied Microbiology and Biotechnology - A comparative study was made on catabolite repression of acid protease and polygalacturonase in an adenine-requiring mutant of Aspergillus niger. Both...     

Protoplast Fusion of Trichoderma reesei, Using Immature Conidia

Protoplast fusion of strains derived from Trichoderma reesei QM9414 and QM9136 and the segregation of the resulting fusants were studied. Combinations of protoplasts prepared from young conidia with double amino acid requirements, one of which was a common requirement and the other uncommon, were fused in the presence of polyethylene glycol 6000. Fusants were selected as regenerant colonies requiring only the commonly deficient amino acid. The frequency of fusion was 0.9 × 10⁻⁴ to 4.0 × 10⁻⁴ for the starting conidia and 3.0 × 10⁻² to 4.9 × 10⁻² for the regenerated protoplasts, which was significantly higher than the expected reversion frequencies by mutation. Conidia generated on the fusant colonies showed diverse phenotypes, i.e., parental types (40 to 80%) and nonparental types (20 to 60%). Colonies developed from single conidia of the nonparental phenotype contained special spots called “knobs” that have a higher density of mycelia. The phenotype of the knobs was again varied among prototrophs, parental types, and recombinant types; and their traits were inherited stably. The phenotype of the mycelia in the nonknob part was essentially the same as that of the original conidia and again formed knobs in colonies upon transfer of a piece of mycelia to a fresh medium. The conidial DNA content of the knob clone was almost the same as that of the parents, but that of the fusants was 1.2 to 2.0 times higher than that of the parents. From these results, we conclude that knobs are the segregants from the fusants. One knob clone showed twice the carboxymethyl cellulose hydrolyzing activity of the parents, suggesting the possibility of breeding T. reesei cells by the protoplast fusion technique.     

Draxin,an axon guidance protein,affects chick trunk neural crest migration

The neural crest is a multipotent population of migratory cells that arises in the central nervous system and subsequently migrates along defined stereotypic pathways. In the present work, we analyzed the role of a repulsive axon guidance protein, draxin, in the migration of neural crest cells. Draxin is expressed in the roof plate of the chick trunk spinal cord and around the early migration pathway of neural crest cells. Draxin modulates chick neural crest cell migration in vitro by reducing the polarization of these cells. When exposed to draxin, the velocity of migrating neural crest cells was reduced, and the cells changed direction so frequently that the net migration distance was also reduced. Overexpression of draxin also caused some early migrating neural crest cells to change direction to the dorsolateral pathway in the chick trunk region, presumably due to draxin’s inhibitory activity. These results demonstrate that draxin, an axon guidance protein, can also affect trunk neural crest migration in the chick embryo.     

Ectopic expression of a horseradish peroxidase enhances growth rate and increases oxidative stress resistance in hybrid aspen

We previously demonstrated that overexpression of the horseradish (Armoracia rusticana) peroxidase prxC1a gene stimulated the growth rate of tobacco (Nicotiana tabacum) plants. Here, the cauliflower mosaic virus 35S::prxC1a construct was introduced into hybrid aspen (Populus sieboldii x Populus grandidentata). The growth rate of these transformed hybrid aspen plants was substantially increased under greenhouse conditions. The average stem length of transformed plants was 25% greater than that of control plants. There was no other obvious phenotypic difference between the transformed and control plants. Fast-growing transformed hybrid aspen showed high levels of expression of prxC1a and had elevated peroxidase activities toward guaiacol and ascorbate. However, there was no increase of the endogenous class I ascorbate peroxidase activities in the transformed plants by separate assay and activity staining of native polyacrylamide gel electrophoresis. Furthermore, calli derived from the transformed hybrid aspen grew faster than those from control plants and were resistant to the oxidative stress imposed by hydrogen peroxide. Therefore, enhanced peroxidase activity affects plant growth rate and oxidative stress resistance.     

The expression of aristaless-related homeobox in neural progenitors of gyrencephalic carnivore ferrets

Aristaless-related homeobox (ARX) has important functions in the development of various organs including the brain. Mutations of the human ARX gene have been associated with malformations of the cerebral cortex such as microcephaly and lissencephaly. Although the expression patterns of ARX in the lissencephalic cerebral cortex of mice have been intensively investigated, those in expanded gyrencephalic brains remained unclear. Here, we show the expression patterns of ARX in the developing cerebral cortex of gyrencephalic carnivore ferrets. We found that ARX was expressed not only in intermediate progenitor (IP) cells but also in outer radial glial (oRG) cells, which are neural progenitors preferentially observed in the gyrencephalic cerebral cortex. We found that the majority of ARX-positive oRG cells expressed the proliferating cell marker Ki-67. These results may indicate that ARX in oRG cells mediates the expansion of the gyrencephalic cerebral cortex during development and evolution.