Field Assessment of Outcrossing from Transgenic Pea (Pisum Sativum L.) Plants
The frequency of outcrossing from a transgenic line of peas into three cultivars ('Carneval', 'Montana', 'Tipu') was studied in the field in 1997 and 1999. Two dominant traits, normal leaf form and a highly-expressed β-glucuronidase (gusA) gene, were used as markers of pollen transfer. Because of heterogeneity in the commercial seed sources, leaf form alone was unreliable for assessing pollen migration into 'trap' plants. Of approximately 9000 offspring tested, only five plants scored positive for the presence of both markers. All five were located in 'trap' plots situated near the transgenic line. This represents a mean outcrossing rate of 0.07%.
OUTCROSSING IN RAPE AND MUSTARD UNDER SASKATCHEWAN PRAIRIE CONDITIONS
The interplant outcrossing rate was studied for one cultivar and four lines of rape (Brassica napus) and three cultivars of mustard (Brassica juncea) under field conditions at Saskatoon, Saskatchewan, in 1982, 1983 and 1984. Marker characters used for determining outcrossing rates were seed oil erucic acid content for rape and seed color for mustard. The average interplant outcrossing rate was 21.8% for rape and 18.7% for mustard. No significant differences in outcrossing rates among the one cultivar and the four lines of rape or the three cultivars of mustard were detected. A wide range in outcrossing rates between plants within cultivars and lines was observed for both species, but whether this variation was genetic or was environmentally induced could not be determined in these experiments. Some of the implications of this partial outcrossing on methods used for the breeding of these crops are discussed.Key words: Outcrossing, rape, mustard
Calyculins and Related Marine Natural Products as Serine-Threonine Protein Phosphatase PP1 and PP2A Inhibitors and Total Syntheses of Calyculin A, B, and C
Calyculins, highly cytotoxic polyketides, originally isolated from the marine sponge Discodermia calyx by Fusetani and co-workers, belong to the lithistid sponges group. These molecules have become interesting targets for cell biologists and synthetic organic chemists. The serine/threonine protein phosphatases play an essential role in the cellular signalling, metabolism, and cell cycle control. Calyculins express potent protein phosphatase 1 and 2A inhibitory activity, and have therefore become valuable tools for cellular biologists studying intracellular processes and their control by reversible phosphorylation. Calyculins might also play an important role in the development of several diseases such as cancer, neurodegenerative diseases, and type 2-diabetes mellitus. The fascinating structures of calyculins have inspired various groups of synthetic organic chemists to develop total syntheses of the most abundant calyculins A and C. However, with fifteen chiral centres, a cyano-capped tetraene unit, a phosphate-bearing spiroketal, an anti, anti, anti dipropionate segment, an α-chiral oxazole, and a trihydroxylated γ-amino acid, calyculins reach versatility that only few natural products can surpass, and truly challenge modern chemists’ asymmetric synthesis skills.