Cysteine proteinases and somatic embryogenesis in suspension cultures of orchardgrass (Dactylis glomerata L.).

摘要

Somatic embryogenesis in cell suspension cultures provides a good model system for investigating early plant development. The conditioned medium harbors a complex array of molecules, mainly derived from the cell walls, which may exert a promotive or inhibitory effect on embryo development. Cell wall proteome and secretome analysis of Arabidopsis, Oryza sativa, Nicotiana tabacum, Medicago sativa and Vitis showed the presence of an unexpected large number of proteases in the cell wall and the culture medium with putative signaling function. Sodium dodecyl sulphate (SDS) - polyacrylamide gel copolymerized with gelatin was used for one-dimensional (1D) and two-dimensional (2D) - electrophoresis to analyze the proteases from the medium of embryogenic suspension cultures of Dactylis glomerata L. during early stages of somatic embryogenesis and non-embryogenic suspension cultures during unorganized cell proliferation. A varying set of acidic protease isoenzymes accompanied the development of both lines. Based on the sensitivity to specific protease inhibitors, a 70 kDa serine proteinase and several 36 kDa cysteine proteinase isoforms (pI 4-5.5) were identified. The 70 kDa serine proteinase was found in the medium and the cell wall of the embryogenic and non-embryogenic cell lines during all stages of development. Interestingly, the 36 kDa cysteine proteinase isoforms were present in the extracellular proteins from the medium and the ionically bound cell wall fraction of the embryogenic cell lines only. We suggest that the enzyme(s) may play an essential role for early somatic embryo development.