Cloning and characterization of aCOBRA-like gene expressedde novoduring maize germination

Abstract

AbstractThe search for germination-specific genes has been a laborious and unrewarding task, since many of the genes expressed during germination are also expressed in embryogenesis or in other developmental stages. By using mRNA differential display of transcript populations from maize (Zea maysL.) embryo axes, germinated for different times with or without a previous osmopriming treatment, a 682 bp cDNA was isolated that was present only after 24 h germination, and absent during osmopriming or during early germination. Screening of a cDNA library using the 682 bp probe yielded a 1554 bp cDNA that contained an open reading frame coding for 436 amino acids. This gene, referred to asZmAA9-24, was expressed in root tissues, but was not detected in shoot or leaf tissues. Expression ofZmAA9-24occurred earlier during germination (by 15 h) if embryo axes were imbibed in the presence of cytokinins or if seeds were previously osmoprimed. The predicted protein sequence ofZmAA9-24is 39.6% identical to the product of the recently identifiedArabidopsisgeneCOBRA(54.5% in the central region), which appears to participate in the regulation of cell expansion, particularly in roots, and belongs to the glycosylphosphatidylinositol (GPI)-anchored protein family.ZmAA9-24expression might be regulated by both cell expansion and the cell cycle, processes that have a central role during seed germination.