31 Molecular Genetics of Amino Acid, Nucleotide, and Vitamin Biosynthesis

Abstract

The study of plant intermediary metabolism has recently been energized by recruitment of the techniques of genetics and molecular biology. This is an interesting field of study in plant biology because there are a number of special uses that plants make of amino acids, nucleotides, and their biosynthetic intermediates, in addition to their role in protein and nucleic acid biosynthesis. These include synthesis of secondary metabolites, such as flavonoids and the hormones auxin, cytokinin, and ethylene; the structural lignins; and the nitrogen storage compounds known as ureides. A deeper understanding of the regulation of these primary metabolic pathways should provide strategies for manipulating such agronomic traits as nutritional quality, growth rate and morphology, and environmental stress susceptibility. Studies of the regulation of metabolic pathways and coregulation of primary and secondary metabolism should lead to insights about the molecular genetic mechanisms governing complex processes in plants.

This is not an exhaustive literature review. Instead, we focus on some pathways that are of particular interest to plant biologists and about which a reasonable amount of biochemical, molecular, or genetic information is available. Whenever possible, work on Arabidopsis thaliana is highlighted, or mention is made of important questions that could be answered using Arabidopsis. We encourage interested readers to consult the recent review articles cited throughout the text to obtain more details.

AMMONIUM ASSIMILATION INTO AMINO ACIDS
Genetic Analysis of the GS-GOGAT Cycle
The nitrogen atoms incorporated into amino acids, nucleotides, and vitamins are ultimately derived from ammonium. This is generated by a...