A SPRUCE GENE, AF70, CONSTITUTIVELY EXPRESSED IN SOMATIC EMBRYOS AND INDUCED BY ABA AND LOW-TEMPERATURE IN SEEDLINGS

We have previously shown that abscisic acid (ABA) specifically induces the secretion of a protein (AF70) in well-developed group a somatic e mbryos of Picea abies (Sabala et al. 1996). In the present work the ge ne for this protein has been isolated and completely sequenced. Homolo gy in amino acid sequence of the AF70 protein and deduced amino acid s equence from the af70 clone and results from Southern blot analysis su ggest that the clone codes for the AF70 protein isolated previously. T here are strong indications that the AF70 protein undergoes several po st-transcriptional modifications characteristic of secreted proteins. The af70 gene is expressed in group A and group B somatic embryos as w ell as in nonembryogenic calluses, but the expression in somatic embry os is not regulated by ABA. In contrast, seedlings of Picea abies do n ot express this gene under normal conditions, but do so in response to cold treatment as well as to ABA treatment. Furthermore, during cold acclimation, achieved when the seedlings are cultured at 20 degrees C under long night conditions, the gene is expressed.