The molecular basis of morphogenesis in plants - The making of the Arabidopsis flower

Morphogenesis is a subject that has attracted the attention of plant biologists for long. The development of tissue culture technique - combined with the discovery and use of various plant hormones - enabled differentiation of calli into plantlets with normal roots, stems and leaves, and serves as the base of modern plant biotechnology. Nevertheless, a deeper insight into the genetic basis of morphogenesis has been gained only in the last decade or so. The isolation of the first homeotic genes in Drosophila in the eighties, spurred new interest in studying the molecular basis of homeotic transformation, known in plants for more than a century. This article traces the beginning of work on homeotic genes in Antirrhinum. In the nineties, however, work on Arabidopsis gained rapid momentum. Accordingly, studies on the development of the Arabidopsis flower leading to the isolation of genes such as AGAMOUS, APETALA 1, 2 and 3, PISTILLATA and LEAFY are discussed in greater detail. Homeotic genes control the expression of many ordinary genes downstream; however, often homeotic genes themselves are under hierarchical control of other homeotic genes upstream. Also touched upon briefly is the usefulness of these studies to biotechnology.