Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 5.24

ANALYSIS OF EMBRYO-SPECIFIC MUTANTS IN MAIZE REVEALS THAT EARLY ARREST IN MAIZE EMBRYOGENESIS IS ASSOCIATED WITH IRREGULAR CELL DIVISIONS

CONSONNI G., BARBANTE A., BRETTSCHNEIDER R., ASPESI C., DOLFINI S., GIULIANI C., GIULINI A., HANSEN S., PILU R., GAVAZZI G.

Dipartimento di Produzione Vegetale, Università degli Studi di Milano, Via Celoria 2, 20133 Milano

emb mutants, embryogenesis, morphogenesis, program cell death, Zea mays

The process that, following embryogenesis, leads to embryo formation appears to follow a defined pattern whose sequential developmental steps under strict genetic control can be analyzed through the analysis of mutants affecting embryogenesis. In this paper we present the analysis of four embryo specific (emb) mutants of maize arrested at the proembryo or early transition stage and defining five separate genes on the basis of their chromosomal location and complementation pattern.

A common feature emerging from their histological analysis is that suppression of morphogenesis is accompanied by an uncontrolled pattern of cell division, an indication that cell division and differentiation are interconnected events. The block in embryo development is associated with an abnormal suspensor proliferation possibly due to the absence of a signal elaborated by the embryo proper and required for suspensor cell identity maintenance.

Mutant endosperm development is not impaired as shown by the formation of the expected domains, i.e. the aleurone, the starchy endosperm, the embryo surrounding region and the basal endosperm transfer layer.

The program of cell death appears impaired in the mutants, as expected if this process is essential in determining the shape and morphology of the developing organs.

An unexpected result is obtained when mutant embryos rescue is attempted. Immature embryos in fact transferred to a basal medium germinate yielding small but otherwise normal seedlings, an observation not consistent with the histological evidence of a complete absence of morphogenetic potential.

The analysis of emb mutants appears a promising tool to elucidate crucial points of embryo development such as the coupling of cell division with morphogenesis, the cell to cell interactions, the relationship between embryo and endosperm development and the interaction between embryo proper and suspensor.