Genetic modification of plant cell walls Selection of genetic mutants and transgenic plants that targets cell wall modification has been considered to enhance biomass enzymatic digestibility. However, as plants have to generate a complex wall-network enabling to complete life cycles rather than to meet biofuel purpose, it remains a challenge to maintain plant normal growth and mechanical strength with high biomass yields. To address this challenge, the identification of appropriate genes is a crucial initial step, and the genetic engineering Y. Wang et al. / Biotechnology Advances 34 (2016) 997–1017 1005 approach used must include appropriate promoters and effective systems for gene transformation and genetic mutagenesis. To date, more than one thousand genes are thought to involve in cell wall biosynthesis, degradation and modification, but only a small number of these genes have been characterized, as shown in Table 3. Based on the functions of these genes, potential genetic approaches are described in this section.