OsSUS3 Overexpression in Rice Leads to Enhanced Biomass Saccharification and Lodging Resistance

Recalcitrance and plant lodging are two traits associated with plant cell wall features. While genetic modification of cell walls can reduce recalcitrance, it is still a challenge to maintain a normal plant growth with enhanced biomass yield and lodging resistance in rice. Sucrose synthase (SUS) is an enzyme regulating carbon partitioning in plants. Although SUS transgenic plants have exhibited improvement on cellulose and starch based traits, little is known about SUS effects on recalcitrance and lodging resistance.

Chunfen Fan from Huazhong Agricultural University selected the transgenic rice plants that expressed OsSUS3 genes that promote secondary cell wall cellulose synthesis in Arabidopsis. The team then examined biomass saccharification and lodging resistance in the transgenic plants.

Transgenic plants maintained a normal growth with slightly increased biomass yields. The four independent transgenic lines exhibited much higher biomass enzymatic saccharification and bioethanol production under chemical pretreatments compared with the control rice cultivar. Notably, all transgenic lines showed a consistently enhanced lodging resistance.

Further analysis revealed that the reduced cellulose crystallinity was a major factor for the enhanced biomass saccharification and lodging resistance in transgenic rice. Moreover, cell wall thickenings with the increased cellulose and hemicelluloses levels also contributed to plant lodging resistance.

This study showed that the SUS3 transgenic rice plants exhibited largely improved biomass saccharification and lodging resistance by reducing cellulose crystallinity and increasing cell wall thickness.