Isolation of two somatic embryogenesis-related genes from orchardgrass (Dactylis glomerata)

Orchardgrass (Dactylic glomerata L.) leaf segments have a high capacity for direct embryogenesis from mesophyll cells and indirect embryogenesis through callus. Total RNA extracted from leaf cultures of embryogenic and nonembryogenic genotypes were used to generate two differentially expressed cDNA fragments. An embryogenic leaf culture cDNA library was screened with these fragments and two somatic embryogenesis-related genes designated DGE1 and DGE2 (for Dactylis glomerata embryogenesis) were identified. RNA blot analysis showed that the DGEs were expressed in embryogenic but not in nonembryogenic leaf cultures. DGE1 transcripts were detected in leaf cultures induced for direct and indirect embryogenesis, while DGE2 was found only in leaf cultures induced for direct embryogenesis. A 90 as segment of DGE1 showed 81% identity with the WRKY DNA-binding protein 21 from Arabidopsis thaliana and contained the WRKY DNA-binding domain. The entire DGE2 sequence had no significant homology with any sequences contained in the Gene Bank. Both genes encode proteins with putative nuclear localization sequences. Collectively, our data indicate that DGE1 and DGE2 are somatic embryo genesis-related genes with possible nuclear regulatory functions. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.