A BRASSICA-NAPUS MESSENGER-RNA ENCODING A PROTEIN HOMOLOGOUS TO PHOSPHOLIPID TRANSFER PROTEINS, IS EXPRESSED SPECIFICALLY IN THE TAPETUM AND DEVELOPING MICROSPORES

The E2 cDNA was isolated by differential screening of a Brassica napus library made from anthers of 1.8-4 mm in length. Northern gel and RNA dot blot analysis revealed that the E2 cDNA hybridised to a 0.7-kb mRNA transcript in RNA extracted from anthers and extruded immature microspores. High expression is limited to the microspore development phase. In situ hybridisation indicated that E2 transcript is also expressed within the tapetal cells. The sequence of 658 nucleotides was determined from clone E2B containing one major open reading frame, encoding a putative protein of M(r) 12.5 kDa. This protein is cysteine rich, encodes a potential signal sequence and shows high homology with plant phospholipid transfer proteins.