Enhancement of Saccharification by Overexpression of Poplar Cellulase in Paraseianthes falcataria

Abstract

Paraserianthes falcataria is known to be one of the fastest-growing tropical trees on the earth. The tree grows symbiotically with nitrogen-fixing Rhizobium and phosphorus-promoting mycorrhizal fungi. We produced the transgenic trees overexpressing poplar cellulase. They did not decrease the level of cellulose but wall-bound xyloglucan in the walls. Such a cell wall modification not only accelerated growth by increasing plastic extensibility but also brought changes in opening and closing movements of their leaves, which were caused by expansion and contraction of motor cells. Nevertheless, the levels of enzymatic cellulose degradation were higher in the transgenic trees than that in the wild-type tree. We suggest that the enhancement of saccharification could be caused by a decrease in xyloglucan cross-linkings between cellulose microfibrils.