CHARACTERIZATION OF A MESSENGER-RNA THAT ACCUMULATES DURING DEVELOPMENT OF OILSEED RAPE PODS

Dehiscence of oilseed rape pods, commonly known as pod shatter, is a p rocess of agronomic importance that results in seed loss causing yield reductions and carry-over of the crop into the following growing seas on. In an effort to understand the mechanisms underlying this developm ental event, the changes in gene expression that accompany pod shatter have been examined with a view to understanding how the process is re gulated. In order to achieve this, a cDNA library was constructed usin g mRNA extracted from the dehiscence zone of developing pods. Differen tial screening with non-dehiscence zone cDNA led to the isolation of a pod-specific clone, SAC25, with a transcript size of 1100 nucleotide encoding a predicted polypeptide of 34 kDa. The level of SAC25 mRNA ac cumulation increased during pod development. The sequence shows no sig nificant homology to others within the databases but has two identifia ble amino acid motifs, one is an adenine nucleotide binding site for N AD/FAD dehydrogenases and the other is a conserved feature of the ribi tol dehydrogenase family. The amino acid sequence has four putative gl ycosylation sites and contains four cysteine residues. Genomic Souther n analysis indicates that SAC25 may be encoded by a single gene or a s mall gene family. The function of this mRNA is unknown but possible ro les in dehiscence and pod development are discussed.