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

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

VIVIPAROUS MUTANTS IN MAIZE

SIRIZZOTTI A., CONSONNI G., GAVAZZI G.

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

mais@mailserver.unimi.it

Abscissic acid (ABA) plays a major role in adaptation to abiotic environmental stresses, seed development and germination. Embryos of ABA deficient or insensitive mutants (vp) exhibit precocious germination or vivipary. These mutants represent a tool to investigate the biosynthesis and the action of ABA in seed development. They are generally classified in two classes, one including mutants impaired in ABA synthesis and another one including those exhibiting a reduced sensivity to the hormone.

We will present data on the characterization of several vp mutants that we have identified and we will classify them on the basis of their response to exogenous ABA and of their endogenous hormone content. The pattern of ABA inducible genes of the mutants will be determined by Northern analysis. Emphasis will be given to those impaired in their ABA sensitivity since they represent mutational events at loci not previously identified and look promising candidates for the identification of the receptor(s) or steps involved in ABA signal transduction.

One of these mutants, rea (red embryonic axis) confers a red pigmentation to the embryonic axis, is occasionally viviparous and is less sensitive than wild-type to the inhibiting effect of exogenous ABA on germination and seedling elongation. This result seems to indicate that the mutation affects ABA sensitivity since no difference in ABA content was detected in mutant versus normal tissues. The mutant maps to 3.06 bin which also contains some interesting QTLs for ABA response. Dr. Helentjaris working at the Pioneer Hi-Breed Int. using a heterologous probe from Arabidopsis isolated the maize homologue for farnesyl transferase b-subunit, which also maps to this same bin. The gene of Arabidopsis named era has been classified as an ABA response gene on the basis of its mutant phenotype. Even though this mutant has surprisingly the opposite phenotype of rea, exhibiting an increased sensitivity to ABA, we are using the maize homologue of the b-FTase gene, a gift of dr. Helentjaris, to test its identity to the rea gene.