PHYSIOLOGIA PLANTARUM 81: 267-272. Coptaibagen 1991 The molecular genetics of seed maturation in maize Donald R. McCarty and Christian B. Carson McCarty, D. R. and Carson, C. B. 1991. The molecular genetics of seed maturation in maize. - Physiol. Plant. 81: 267-272. The maturation phase of seed formation involves coordinated expression of multiple developmental pathways. These processes include absdsic add regulated responses associated with the arrest of embryo development and induction of anthocyanin synthesis in embryo and aleurone tissues. Studies of the maturation defective vivapa- raus mutants of maize suggest that one gene, viviparous-! (vpl), regulates both of these pathways in the developing seed. Mutations at vpl reduce the sensitivity of the developing embryo to abscisic aeid. In addition, Vpl is required for expression oiCl, a regulatory gene for the anthocyanin pathway. This interaction is consistent with the idea that Vpl and CI function as part of a regulatory hierarchy controlling seed development. Molecular studies of vpl mutations which separate control of embryo arrest and anthocyanin synthesis suggest that these functions map to discrete domains in the Vpl protein. Therefore, coordinate control of diverse maturation processes may be achieved through expression of a functionally complex regulatory molecule. Key words — Abscisic acid, anthocyanin synthesis, desiccation tolerance, maturation, vivipary. D. R, McCarty (corresponding author) and C, B. Carson, Vegetable Crops Dept, IFAS, Univ. of^Florida, Gainesville, FL 32611, USA. This paper is part of the contribution to the 1990 Annual Symposium of the Southem Section of the American Society of Plant Physiologists, held in Biloxi. MS, USA, 4-6 March, 1990. Introduction Formation of the seed involves a complex interplay of many diverse developmental processes, beginning with the earliest events in embryogenesis and tissue differ- entiation and ending with maturation and establishment of developmental arrest. Mutations that affect seed de- velopment provide a powerful means of studying the genes that control these events. In this respect, mutants of maize have been particularly valuable in identifying genes involved in the maturation phase of seed forma- tion. These include vivipary genes that affect abscisic acid mediated responses and the genes that control ex- pression of anthocyanin pigment in seed tissues late in development. Genetic studies suggest that the vivipa- rotis-1 (vpl) gene regulates both of these pathways in the developing seed. Therefore, functions associated with developmental arrest and pigment synthesis may be subsets of a broader developmental program con- Received 11 September, 1990 Pfaysiol. Plant. 81, 1991 trolled by Vpl, The Vpl gene and key regulatory genes for the anthocyanin pathway have recently been cloned by transposon tagging. These genes provide a unique opportunity for study of a regulatory gene hierarchy in a plant system. The role of ABA and the vivipary genes in controlling maturation and the hierarchial interaction between Vpl and regulatory genes controlling the an- thocyanin pathway are reviewed here. Mutants afTecting maturation Maturation occurs in the mid to late phase of seed foimation as the embryo acquires tolerance to dedica- tion and grovrth is gradually arrested. In maize and cereal grains the aleurone layer of the endosperm also is destined to remain viable in the dry seed and therefore must undergo a maturation process. In the embryo, maturation is marked by the accumulation of a charac- teristic set of proteins (Quatrano 1987). Synthesis of 267