Genes Induced by Abscisic Acid and Water Stress in Maize

PAGES M, LUDEVID MD, VILARDELL J, FREIRE MA, PLA M, TORRENT M, GODAY A

Plant Molecular Biology 2

Springer

Año: 1991; p. 651 - 661

The plant hormone abscisic acid (ABA) appears to modulate the responses of plants under conditions of water deficit (Davies and Mansfield, 1983). In general, there are two basic types of response to ABA which have been correlated with regulation of gene expression. First, a slow response during angiosperm embryo development (Quatrano, 1986), with ABA levels increasing (Jones and Brenner, 1987) during the embryogenic period prior to the desiccation of the embryo, and inducing the synthesis of specific proteins and mRNAs (Galau et al. 1987, Sanchez-Martinez et al. 1986). Second, a rapid response in water-stressed plant tissues where the level of ABA increases (Wright and Hiron, 1969) and alters the level of specific gene expression (Heikkila et al. 1984).In earlier studies on the regulation of gene expression during embryogenesis in Zea mays L we have described the expression of a set of specific polypeptides which were rapidly induced by ABA in young embryos upon hormone treatment (Sanchez-Martinez et al. 1986). These polypeptides also appear during normal embryogenesis when the development of the embryo is progressing to the maturation stage, coinciding with the period when the endogenous level of ABA attains a maximum. After accumulating in dry embryos these polypeptides disappear during the first hours of germination (Goday et al. 1988)cDNAs and genomic clones corresponding to two proteins, RAB-17 and MAH9, were obtained (Vilardell et al. 1990, Gomez et al. 1988). Northern blot hybridization showed that these genes are involved in generalized plant ABA responses, as their products accumulate in leaves under conditions of water-deficit (Pla et al. 1989, Vilardell et al. 1990).The mode of action of the hormone remains unclear. Functional analyses using transient systems and transgenic plants have identified ABA-responsive DNA elements in the promoters of different ABA-regulated genes (Marcotte et al. 1989, J. Vilardell, unpublished). However, current evidence suggests that more than one mechanism may determine the level of expression of various ABA-responsive genes, and some of the ABA-regulated proteins seem to be functionally unrelated.