MOLECULAR-CLONING OF THE CDNA CODING FOR THE (R)-(-MANDELONITRILE LYASE OF PRUNUS-AMYGDALUS - TEMPORAL AND SPATIAL EXPRESSION PATTERNS IN FLOWERS AND MATURE SEEDS())

A gene highly expressed in the floral organs of almond (Prunus amygdal us Batsch), and coding for the cyanogenic enzyme (R)-(+)-mandelonitril e lyase (EC 4.1.2.10), has been identified and the full-length cDNA se quenced. The temporal expression pattern in maturing seeds and during floral development was analyzed by RNA blot, and the highest mRNA leve ls were detected in floral tissues. The spatial mRNA accumulation patt ern in almond flower buds was also analyzed by in-situ hybridization. The mRNA levels were compared during seed maturation and floral develo pment in fruit and floral samples from cultivars classified as homozyg ous or heterozygous for the sweet-almond trait or homozygous for the b itter trait. No correlation was found between these characteristics an d levels of mandelonitrile lyase mRNA, suggesting that the presence of this protein is not the limiting factor in the production of hydrogen cyanide.