JXB Advance Access originally published online on January 22, 2007
Journal of Experimental Botany 2007 58(5):1197-1205; doi:10.1093/jxb/erl290
RESEARCH PAPER |
A mutational approach to the study of seed development in maize
1Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italia
2Dipartimento di Produzione Vegetale, Università degli Studi di Milano, Via Celoria 2, 20133 Milano, Italia
To whom correspondence should be addressed. E-mail: giuseppe.gavazzi{at}unimi.it
The maize seed comprises two major compartments, the embryo and the endosperm, both originating from the double fertilization event. The embryogenetic process allows the formation of a well-differentiated embryonic axis, surrounded by a single massive cotyledon, the scutellum. The mature endosperm constitutes the bulk of the seed and comprises specific regions containing reserve proteins, complex carbohydrates, and oils. To gain more insight into molecular events that underlie seed development, three monogenic mutants were characterized, referred to as emp (empty pericarp) on the basis of their extreme endosperm reduction, first recognizable at about 12 d after pollination. Their histological analysis reveals a partial development of the endosperm domains as well as loss of adhesion between pedicel tissues and the basal transfer layer. In the endosperm, programmed cell death (PCD) is delayed. The embryo appears retarded in its growth, but not impaired in its morphogenesis. The mutants can be rescued by culturing immature embryos, even though the seedlings appear retarded in their growth. The analysis of seeds with discordant embryo–endosperm phenotype (mutant embryo, normal endosperm and vice-versa), obtained using B–A translocations, suggests that emp expression in the embryo is necessary, but not sufficient, for proper seed development. In all three mutants the picture emerging is one of a general delay in processes related to growth, as a result of a mutation affecting endosperm development as a primary event.
Key words: Embryo, emp mutants, endosperm, maize, PCD, seed development
* These two authors contributed equally to the present work.
Received 10 May 2006; Revised 17 November 2006 Accepted 4 December 2006