While laccases, multi-copper glycoprotein oxidases, are often able to catalyze oxidation of a broad range of substrates, such as phenols and amines in vitro, their precise physiological/biochemical roles in higher plants remain largely unclear, e.g., Arabidopsis thaliana contains 17 laccases with only 1 having a known physiological function. To begin to explore their roles in planta, spatial and temporal expression patterns of Arabidopsis laccases were compared and contrasted in different tissues at various development stages using RT-PCR and promoter-GUS fusions. Various cell-specific expressions were noted where specific laccases were uniquely expressed, such as LAC4 in interfascicular fibers and seed coat columella, LAC7 in hydathodes and root hairs, LAC8 in pollen grains and phloem, and LAC15 in seed coat cell walls. Such specific cell-type expression patterns provide new leads and/or strategies into determining their precise physiological/biochemical roles. In addition, there was an apparent redundancy of gene expression patterns for several laccases across a wide variety of tissues, lignified and non-lignified, perhaps indicative of overlapping function(s). Preliminary evidence, based on bioinformatics analyses, suggests that most laccases may also be tightly regulated at both transcriptional (antisense transcripts, histone and DNA methylation) and posttranscriptional (microRNAs) levels of gene expression.

The evolution and luminal effects of different quantities of casein and beta-lactoglobulin were investigated in the upper jejunum of 35 volunteers who ingested 400 mL water with either beta-lactoglobulin or casein in either low or high doses (72.6 mmol N, Lbetalg; 71.7 mmol N, LCas; 368.2 mmol N, Hbetalg; 386.8 mmol N, HCas). The flow rate of the liquid effluents as well as the nitrogen movements were measured and the exogenous ([15N]) and endogenous nitrogen fractions analyzed in the upper jejunum after milk protein ingestion. The basal jejunal liquid flow rate (mL/min) was 3.88+/-1.84 and peaked in the 0-20 min period for water (9.92+/-3.72) and Lbetalg (7.27+/-3.08) and during the 20-40 min period for LCas (5.69+/-2.49), HCas (6.32+/-1.85), and Hbetalg (6.11+/-2.31). One hour after water, LCas, Lbetalg, Hbetalg, and HCas ingestion, 100%, 95%, 85%, 71%, but only 38% of the liquid phase of the meal were passed through the jejunum, respectively. The flow rate of the endogenous nitrogen was 12.93+/-5.22 mmol N/h before meal ingestion; remained unchanged after water, LCas or Hbetalg ingestion; but increased significantly (P<0.05) after Lbetalg and HCas ingestion. The net disappearance of exogenous nitrogen in the upper jejunum 240 min after HCas, Lbetalg, LCas and Hbetalg ingestion was 82.6+/-9.5%, 61.6+/-9.6%, 58.4+/-14.7%, and 44.7%+/-24.4%, respectively. The exogenous fraction of protein nitrogen recovered in the upper intestinal lumen represented 43.3% of the ingested Hbetalg nitrogen, but only 4.9% of the ingested HCas nitrogen. In conclusion, casein and beta-lactoglobulin present differences in both the intestinal kinetics of amino acid delivery and in the nature of the products in the intestinal lumen. These differences have to be taken into account from both nutritional and physiologic points of view for the utilization of these proteins in humans.

Mutants of Arabidopsis thaliana with a glucosinolate content different from wild type were isolated by screening a mutagenized population of plants. Six mutants were detected out of a population of 1200 screened. One of these mutants, TUI, was analyzed in detail. Leaf and seed tissues of line TUl lack or have reduced amounts of many of the aliphatic glucosinolates found in the wild type due to a recessive allele, gsml, of a single nuclear gene, GSM1. The seed phenotype is inherited as a maternal effect suggesting that the embryo is dependent on the maternal tissue for its glucosinolates. Experiments involving feeding of "4C-labeled intermediates suggested that the gsml allele results in a metabolic block which decreases the availability of several amino acid substrates required for glucosinolate biosynthesis: 2-amino-6-methylthiohexanoic acid, 2-amino-7-methylthioheptanoic acid, and 2-amino-8-methylthiooctanoic acid. The mutation does not result in any obvious changes in morphology or growth rate. A pathway for the biosynthesis of glucosinolates in A. thaliana is proposed.Glucosinolates are anionic thioglucosides (Fig. 1) synthesized by many species of the order Capparales including all the Brassicaceae (for reviews see refs. 6 and 26). The primary biological function of glucosinolates is unknown, although a role in plant defense against bacterial and fungal pathogens and insect predators has been suggested (reviewed by Fenwick et al. [6]).The presence of glucosinolates in crop species has several important consequences. First, dietary problems in livestock can result when fodder with high levels of glucosinolates are consumed. Thus, glucosinolates severely restrict the amount of glucosinolate-containing meal that can be used in animal feed supplements (24). Second, the distinctive flavor associated with Brassicaceae species which serve as vegetable and

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