Translatable RNA populations associated with maintenance of primary root elongation and inhibition of mesocotyl elongation by abscisic acid in maize seedlings at low water potentials

Abstract

Previous work indicated that accumulation of abscisic acid (ABA) acts differentially to maintain elongation of the primary root and inhibit elongation of the mesocotyl of maize (Zea mays L.) seedlings at low water potentials (ψw) Subsequent results indicated specific locations in the elongation zones where elongation is maintained, inhibited, or unaffected by endogenous ABA at low ψw. This information was utilized in this study to identify in vitro translation products of RNA associated with the maintenance or inhibition of elongation in the primary root and mesocotyl, respectively, by endogenous ABA at low ψw. The results distinguished products associated specifically with the elongation responses from those nonspecifically associated with ABA accumulation or low ψw, as well as normal cell development and maturation. In the primary root, the maintenance of elongation at low ψw by ABA was associated with the maintenance of expression of three products that were also expressed during elongation at high ψw, the expression of a novel product, and the suppression of two products. In the mesocofyl, the inhibition of elongation by ABA after transplanting to low ψw was associated with the induction of a novel translation product. However, the induction of this product, as well as accumulation of ABA and inhibition of elongation, occurred without a decline in tissue water content. The results demonstrate the necessity of examining the association of gene expression with elongation responses to low ψw with a high degree of spatial resolution.