PHOSPHATE-INDUCED 1 and Its Paralogs Positively Regulate Cellulose Biosynthesis in Arabidopsis

Cellulose is not only the most abundant biopolymer on Earth but also an essential multi-purpose resource, primarily synthesized by cellulose synthase complexes (CSCs) located on plasma membrane in vascular plants. Although insights into the functions of CSCs have been provided by the identification of cellulose synthase catalytic subunits, our understanding of the regulation of CSC activity remains limited. In this study, combining molecular and genetic methods, we demonstrated that both PHI-1 and its paralogs residing in the plasma membrane are involved in the cellulose biosynthesis regulation as a positive regulatory component of CSCs by feeding developmental and environmental cues into their activities in Arabidopsis ( Arabidopsis thaliana ). Our finding reveals a mechanism for how plants regulate cellulose synthesis in response to developmental and environmental signals, and thus improves the likelihood that cellulose biosynthesis could be feasibly adapted for sustainable purposes.