Abstract:

The changes in protein patterns were monitored with SDS PAGE and IEF/2D during callus proliferation and adventitious bud differentiation of Populus euphratica. The results showed callus differentiation potential was closely related to its expressed proteins. Callus induced from shoot bases on the medium with the ratio of BA to NAA 1 under light, had a high differentiation capability, and expressed less sorts of proteins than those being subcultured, indicating its differentation degree was lower. Marker proteins for different kinds of calli and different phases of callus differentiation were identified. Two subculture specific markers protein bands, 24.5 kDa and 58.6 kDa, were observed in callus proliferated in dark on the medium with the rate of BA to NAA 0.5. Meanwhile, the 19 kDa and 31 kDa protein bands that expressed during callus differentation were also found in the subcultured callus, suggesting that gradual loss of organogenesis ability of the subcultured callus may be contributed to the increasing of its differentiation. When the callus induced from shoot bases was cultured on the regeneration medium with the ratio of BA to NAA 0.5 under light, it firstly differentiated into a few smaller green meristematic islands in its surface layer, then adventitious shoot primordial from the islands. Two protein bands of 20 kDa and 55?kDa, as distinctive differentiation markers, expressed obviously in the differentiated callus. The 20 kDa protein with pI of 5.5～6.5 was specific to callus differentiation. A 43 kDa protein with pI of 6.5～7.5 generated during the early stage of differentiation. The relation between callus organogenesis potential and its expressed proteins was discussed.

Key words: Populus euphratica, Marker protein, Callus proliferation, Adventitious bud differentation