ISOLATION AND CHARACTERIZATION OF A POD DEHISCENCE ZONE-SPECIFIC POLYGALACTURONASE FROM BRASSICA-NAPUS

Seven distinct partial cDNAs, similar in sequence to previously descri bed polygalacturonases (PGs), were amplified from cDNA derived from ra pe pod wall, dehiscence zone and leaves by the polymerase chain reacti on. Northern analysis showed that one clone, PG35-8, was expressed at low levels in the dehiscence zone during the first five weeks after an thesis but was very abundantly expressed at week 6. In contrast, no PG 35-8-related RNA was detected in the pod wall. Our data suggest that t here are temporal and spatial correlations between the breakdown of th e middle lamella, of the dehiscence zone cells and the pattern of synt hesis of PG35-8 transcripts which may indicate a role for this particu lar PG in rape pod dehiscence. PG35-8 was used to isolate five cDNA cl ones from a rape dehiscence zone cDNA library. Restriction enzyme anal ysis and partial sequencing revealed that they were derived from four highly homologous transcripts which are probably allelic forms of a si ngle gene. One full-length clone, RDPG1, was completely sequenced. The predicted protein of RDPG1 showed its highest identity with PG from a pple fruit with an identity of 52%.