High expression of the xylanase B gene from Clostridium stercorarium in tobacco cells

The xylanase gene (xynB) from Clostridium stercorarium was expressed in tobacco cells (BY2) under the control of the cauliflower mosaic virus (CaMV) 35S promoter. The gene product, xylanase B (XynB), was proteolytically processed in the transformed cells (termed B1-11): a larger form of the protein was mainly found in the culture supernatant and a smaller one was found in the cells. The amount of XynB protein was estimated to be 5% of the total soluble proteins in B1-11 calli after 2 weeks of cultivation. XynB isolated from the transformed tobacco cells had the activity to hydrolyze the cell wall of barley straw.