Mesophyll-specific, light and metabolic regulation of the C4 PPCZm1 promoter in transgenic maize.

To play an essential role in C4 photosynthesis, the maize C4 phosphoenolpyruvate carboxylase gene (PPCZm1) acquired many new expression features, such as leaf specificity, mesophyll specificity, light inducibility and high activity, that distinguish the unique C4 PPC from numerous non-C4 PPC genes in maize. We present here the first investigation of the developmental, cell-specific, light and metabolic regulation of the homologous C4 PPCZm1 promoter in stable transgenic maize plants. We demonstrate that the 1.7 kb of the 5'-flanking region of the PPCZm1 gene is sufficient to direct the C4-specific expression patterns of beta-glucuronidase (GUS) activity, as a reporter, in stable transformed maize plants. In light-grown shoots, GUS expression was strongest in all developing and mature mesophyll cells in the leaf, collar and sheath. GUS activity was also detected in mesophyll cells in the outer husks of ear shoots and in the outer glumes of staminate spikelets. We did not observe histological localization of GUS activity in light- or dark-grown callus, roots, silk, developing or mature kernels, the shoot apex, prop roots, or pollen. In addition, we used the stable expressing transformants to conduct and quantify physiological induction studies. Our results indicate that the expression of the C4 PPCZm1-GUS fusion gene is mesophyll-specific and influenced by development, light, glucose, acetate and chloroplast biogenesis in transgenic maize plants. These studies suggest that the adoption of DNA regulatory elements for C4-specific gene expression is a crucial step in C4 gene evolution.

Structure and development of the pitchers from the carnivorous plantNepenthes alata (Nepenthaceae).

The pitchers of the tropical carnivorous plant Nepenthes alata are highly specialized organs for the attraction and capture of insects and absorption of nutrients from them. This study examined the structure and development of these pitchers, with particular focus on the nectaries and digestive glands. Immature pitchers developed at the tips of tendrils and were tightly sealed by a lid structure that opened during the end of pitcher elongation. Opened pitchers exposed a ridged peristome containing large nectaries. Like other members of the genus, a thick coating of epicuticular waxy scales covered the upper one-third of the pitcher. Scattered within this zone were cells resembling a stomatal complex with a protruding ridge. Cross sections showed that this ridge was formed by asymmetric divisions of the epidermal cells and lacked an underlying pore. The basal region of the trap had large multicellular glands that developed from single epidermal cells. These glands were closely associated with underlying vascular traces and provided a mechanism for supplying fluid to closed immature pitchers.

Organelle isolation by magnetic immunoabsorption.

Currently, most organelle isolation procedures rely on physical parameters and centrifugation for separation. Here, we report the rapid and gentle isolation of a variety of organelles by immunolabeling whole cell lysates with organelle-specific antibodies and streptavidin magnetic particles followed by separation in a magnetic field. Using magnetic immunoabsorption, we have been able to specifically label mouse metaphase chromosomes and a variety of plant organelles, including: amyloplasts, choroplasts and nuclei from whole cell lysates of various plant tissues. We find that the distinct magnetic properties, surface characteristics and mean diameter-size ranges of different particle preparations significantly influence their specific utility for organelle isolations. By using an internal-field magnetic separation device, we have developed a method for quantitative recovery of labeled organelles in microarrays and tested a variety of antibodies to chloroplast outer envelope proteins for their ability to immune-isolate chloroplasts.

School activities and work: effects on adolescent self-esteem.

This study investigated the relationship between participation and involvement in school activities, degree of part-time work, and self-esteem in a sample of middle-class urban high school sophomores and juniors. The results indicated that self-esteem was affected by the nature of the school activity and by gender. Within a multivariate context, results indicated no significant correlates of self-esteem among the boys. Among the girls, the significant correlates of self-esteem were hours worked, age, and curricular track. The differential nature of school activities, gender, and the effects of working outside of school are discussed.