The Genetic Basis of Phenotype Expression in Plants

Abstract

Abstract Recent developments in plant molecular genetics have revealed a direct relationship between gene structure and its function in plant structure, development, response to stimuli, and metabolic pathways. The rapid progress in this field depends mainly on intensive efforts at isolation of a series of mutants using selected model plants, such as Arabidopsis thaliana, snapdragon (Antirrhinum majus), rice (Oryza sativa), and maize (Zea mays). Arabidopsis thaliana is a small crucifer, called “botanical Drosophila” because it has some remarkable features: small genome size, short life‐cycle, small size, and ease of propagation. More than 200 research groups in many countries have isolated mutants defective in the development of embryo, shoot, flower, and root, as well as in response reactions to physical and chemical stimuli such as gravity, light, nutrients, and phytohormones. Some of the Arabidopsis mutants show aberrant structures that may be identified as non‐crucifer characters. For example, a flower mutant, SAKURA. often bears five petals; another mutant, LEUNIG, has no ovarian septum. TERMINAL FLOWER mutant changes indeterminate inflorescence to determinate. Some root mutants do not form lateral roots. Several mutants form one cotyledon. These morphology mutants will provide hints for considering critical genetic changes that may have caused the past evolutionary events.Genes isolated from the morphology mutants are classified into three groups: coding transcription factors, kinases, and other protein motifs. Although the detailed molecular mechanism in the mutants is not known, hierarchical regulatory networks of the genes are being investigated. We will provide examples of the genetic networks at work in organ development, and discuss possible genetic changes that result in drastic morphological variation.