Abstract text: Nitrate is an important nutrient and signal that modulates plant growth and development. In Arabidopsis, nitrate induces cotyledon cell expansion during the first week after germination. Cell expansion is a highly mechanical process that requires changes in cell wall structure and properties. However, how nitrate signaling modulates and coordinates cell wall changes for growth is not well understood. We showed nitrate promotes a highly methylesterified pectin status and reduces cell wall stiffness during shoot growth. Here, we describe how cellulose metabolism participates in nitrate-induced cotyledon cell expansion. We found that CESA3 function is required for nitrate-modulated changes in cellulose during growth. We further show that nitrate signaling regulates cellulose biosynthesis by changes in CESA3 phosphorylation at a specific aminoacid residue. This work supports a model where cellulose metabolism has a role in nitrate-induced cell expansion, which along the reported role of pectin, emphasizes the importance of the interplay between nitrate signaling and cell wall metabolism during shoot growth.

This work was supported by ANID Fondecyt Postdoctorado 3261149, ANID-FONDECYT 11230913, ANID-Millennium Science Initiative Program- Millenium Institute for Integrative Biology (iBio) (ICN_022), ANID- Millennium Science Initiative Program- Millennium Center for Genome Regulation (ICN2021_044), ANID- Programa Proyectos de Exploración 13250100, ANID-FONDECYT 1220594 - N°1261744