We have characterized the 5' region of the rice actin 1 gene (Act1) and show that it is an efficient promoter for regulating the constitutive expression of a foreign gene in transgenic rice. By constructing plasmids with 5' regions from the rice Act1 gene fused to the coding sequence of a gene encoding bacterial beta-glucuronidase, we demonstrate that a region 1.3 kilobases upstream of the Act1 translation initiation codon contains all of the 5'-regulatory elements necessary for high-level beta-glucuronidase (GUS) expression in transient assays of transformed rice protoplasts. The rice Act1 primary transcript has a noncoding exon separated by a 5' intron from the first coding exon. Fusions that lack this Act1 intron showed no detectable GUS activity in transient assays of transformed rice protoplasts. Deletion analysis of the Act1 5' intron suggests that the intron-mediated stimulation of GUS expression is associated, in part, with an in vivo requirement for efficient intron splicing.

http://www.plantcell.org/content/plantcell/2/2/163.full.pdf

Isolation of an efficient actin promoter for use in rice transformation

(I) Inorganic components . . . . . . . (a) Nitrate . . . . . . . . . (b) Cation-anionuptake . . . . . . (2) Organic compounds . . . . . . . (a) Amino acids and other organic nitrogenous compounds (b) Organic acids . . . . . . . . (3) Effects on flowering . . . . . . . (4) Ammonium plus nitrate as a nitrogen source . . . ( 5 ) Metabolic changes characteristic of ammonium toxicity . VII . Summary . . . . . . . . . . VI . Physiological effects of nitrogen sources . . . .

Ammonium and nitrate nutrition of plants

Plants, selenium and human health

Plant tissue culture techniques have become vitally important for pursuing a wide range of fundamental and applied problems in research and development. The techniques encompass a variety of procedures used for specific purposes. The growing of masses of unorganized cells (callus) on agar or in liquid suspension is widely employed in biochemical and growth studies (1-5). The culture of segments of stems, roots, leaves or of callus provides systems to study differentiation, morphogenesis and plant regeneration (6, 7). Shoot apex culture methods leading to plant regeneration have been adopted for plant propagation and production of virusfree stock (8). The culture of anthers and pollen provides new approaches to haploid plant formation (9). Recently the technology has been extended to include the isolation and culture of plant protoplasts which are employed in fusion and somatic cell hybridization (10-13). The development of the various types of tissue culture has been based on empirical approaches, and some of the observations recorded in the literature may not be typical for plant cells. Differences in medium, environment, age, cell origin, and growth rates may explain the behavior of a particular line and need not represent a general characteristic of plant cells in culture. More uniformity in conditions of culture would assist in making data and observations more comparable.

Plant tissue culture media.

Providing a fast growing world population with sufficient food while preserving ecological and energy resources of our planet is one of the biggest challenges in this century. Optimized management of chemical fertilizers and pesticides will be essential for achieving sustainability of intensive farming and requires both empirical data from field trials and advanced fundamental understanding of the molecular processes controlling plant growth. Genes involved in plant responses to nutrient deficiency and pathogen/herbivore attack have been identified, but we are lacking information about the cross-talk between signalling pathways when plants are exposed to a combination of abiotic and biotic stress factors. The focus of this review is on the relationship between the potassium status of plants and their susceptibility to pathogens and herbivorous insects. We combine field evidence on potassium-disease interaction with existing knowledge on metabolic and physiological factors that could explain such interaction, and present new data on metabolite profiles and hormonal pathways from the model plant Arabidopsis thaliana. The latter provides evidence that facilitated entry and development of pathogens or insects in(to) potassium-deficient plants as a result of physical and metabolic changes is counteracted by an increased defence. A genetic approach should now be applied to establish a causal relationship between disease susceptibility on the one hand and individual enzymatic and signal components on the other. Once identified, these can be used to design agricultural strategies that support the nutritional status of the crops while exploiting their inherent potential for defence.

Akio Fujiwara

Papers

Studies on the nutrition of rice cell culture I. A simple, defined medium for rapid growth in suspension culture :

Photoinhibition of elongation growth of roots in rice seedlings

Studies on the nutrition of rice cell culture II. Microelement requirement and the effects of deficiency

Fate of (+)S-methyl-L-cysteine sulfoxide in chinese cabbage, Brassica pekinensis RUPR. :

A short note on the mode of incorporation of sulfur into cellular fractions of barley leaves