Variation and genetics of ribonucleases and phosphodiesterases in conifer seeds

Abstract

Using techniques of starch gel electrophoresis, isoenzymes of ribonuclease 11 (RNase, EC 3.1.4.23) and phosphodiesterase I (PDase, EC 3.1.4.1) could be identified in endosperm tissue from dry seeds of three conifer species: Norway spruce (Picea abies). Scots pine (Pinus silvestris), and Douglas fir (Pseudotsuga menziesii). The RNase patterns mostly exhibited a relatively great number of isoenzyme bands as well as a considerable tree-to-tree variation, whereas the PDase system revealed only one enzyme zone in each of the three seed species. Furthermore, an isoenzyme variation within the PDase zones appeared to be very infrequent and could only be detected in Norway spruce and Douglas fir. However, the isoenzyme patterns of RNase as well as PDase showed significant differences between the conifer species. The genetic basis of the intraspecific isoenzyme variations could be easily analyzed, since the test material (seed endosperm) represented haploid tissues resulting from macrogametophytes after fertilization. Hence, it was possible to identify three polymorphic RNase gene loci in Douglas fir seeds, two in Scots pine seeds, and one in Norway spruce seeds. The PDase zone in each conifer species was controlled by one gene locus which revealed allelic forms only in Norway spruce and Douglas fir seeds.