Newly identified AP2-ERF transcription factors produce thickened primary cell wall in fiber cells of nst1 nst3 double mutant in Arabidopsis

Primary cell wall is an essential cell structure for plant playing major roles in plant growth, differentiation, and stress responses. Here we demonstrate that a group of AP2-ERF transcription factor regulates primary cell wall formation and can induce massive accumulation of it in empty fiber cell of the nst1-1 nst3-1 mutant lacking secondary cell wall in Arabidopsis. The transgenic plants expressing one of the AP2-ERF transcription factors fused with VP16 transcriptional activation domain under the control of NST3 promoter in the nst1-1 nst3-1 mutant showed similar level of cell wall contents with wild type by the massive accumulation of cell wall which lacks lignin and xylan. The transgenic plants showed 70% higher saccharification efficiency than wild type. Gene expression analysis using microarray revealed that genes related to primary cell wall were highly upregulated in the transgenic plant. Moreover, chimeric-activator of the AP2-ERF transcription factor accelerated cell wall regeneration of mesophyll protoplast of Arabidopsis while the chimeric-repressor retarded it. These data suggest that the group of AP2-ERF transcription factor is key regulator of the primary cell wall formation in plant and could be employed to produce massive cell wall with readily extractable feature. Transcriptomes of stem of NST3pro:ERF035-VP16 nst1-1 nst3-1 plant and that of nst1-1 nst3-1 plant were measured to see their difference.