Germination-related genes encoding proteolytic enzymes are expressed in the nucellus of developing wheat grains

During wheat (Triticum aestivum) grain germination the aleurone layer Shows a high expression of genes encoding hydrolytic enzymes. In this study we analyzed the spatio-temporal pattern of expression of two of these genes, a carboxypeptidase III and a thiol protease, in developing grains. Our results show that transcripts of both genes accumulate at early stages of grain development (5-15 dpa) in the nucellus, a maternal tissue that degenerates during wheat grain development. In addition, the thiol protease gene is expressed in the nucellar projections and the modified aleurone cells, the cellular pathway of photosynthate transfer in the developing wheat grain. These results show that genes related to the germination programme are also expressed in the development programme where they may be implicated in the degenerative process that takes place in the nucellar tissue and the cytoplasm of nucellar projections cells.