Comparative study of cellulases associated with adventitious root initiation, apical buds, and leaf, flower, and pod abscission zones in soybean.

Cellulase activity was measured in soybean (Glycine max) leaf abscission zones, flower abscission zones, pod abscission zones, apical buds, and adventitious rooting hypocotyls. Immunoprecipitation data showed that a cellulase immunologically similar to the bean abscission cellulase (isoelectric point 9.5) is present in soybean leaf, flower, and pod abscission zones, but is not present in soybean apical buds or rooting hypocotyls. cDNA and genomic clones for two different soybean genes were identified and show sequence similarity with the bean abscission cellulase clone pBAC10. The cDNA clone pSAC1, isolated from a soybean abscission cDNA library, hybridized to transcripts in soybean leaf, flower, and pod abscission zones. Although ethylene has been shown to play a role in the increase in cellulase activity associated with both abscission and adventitious root initiation, no signal was seen for hybridization of the soybean abscission cellulase clone, pSAC1, to RNA from soybean adventitious rooting hypocotyls. In addition, no soybean abscission cellulase transcripts were detected in apical buds. Transcripts for a second soybean cellulase gene (SC2) were not detected in any of the tissues surveyed.