Characterization of an mRNA encoding a polygalacturonase expressed during pod development in oilseed rape (Brassica napusL.)

Pod shatter in oilseed rape is associated with the degradation of the pectin-rich middle lamella at the site of dehiscence. It has been reported that, accompanying pod development, there is an increase in the activity of polygalacturo nase (EC 3.2.1.15) and that this rise is restricted to the tissue undergoing cell separation. Using a PCR strategy a fragment of a polygalacturonase encoding an mRNA that is up-regulated specifically in the dehiscence zone tissue during pod development has been cloned. A full length clone (SAC66) complementary to this mRNA has been isolated from a dehiscence zone cDNA library and sequenced. The mRNA encoded by SAC66 shares significant amino acid homology with endopolygalacturonases from fruit of Actinidia deliciosa and Lycopersicon esculentum. The transcript size of the SAC66 mRNA is 1.7 kb. Northern analysis has revealed that expression of SAC66 mRNA increases at 30 d after anthesis (DAA), reaching a plateau at 45 DAA, and that the up-regulation is restricted to the site where dehiscence takes place.