Calling for reinforcements: the role of TTL proteins in the regulación of cell wall biosynthesis

Abstract

Cellulose is the most abundant organic compound of all biomass on Earth1, with highly relevant roles in plant development and defence. Hence, it is essential to understand the regulation of its biosynthesis to improve the crop's tolerance to biotic and abiotic stresses. Tetratricopeptide Thioredoxin-Like (TTL)2 proteins have been identified as new players in regulating the cellulose synthase complex (CSC), uncovering their dynamic association with the CSC under cellulose-deficient conditions3. We show that TTLs are essential to maintain cellulose synthesis under salt stress, mediated by a reinforced cortical microtubule array and the stabilization of the CSCs at the plasma membrane. To perform this, TTLs interact with Cellulose Synthase 1 and promote microtubules polymerization. This dynamic behaviour of TTLs is not specific to salinity stress, and other factors that cause defects in cellulose also cause the re-localization from the cytosol to the CSC. We conclude that TTLs act as intermediates between stress sensing and the regulation of cellulose biosynthesis to overcome adverse environmental conditions. We are now investigating how changes in phosphorylation of the Intrinsic Disordered Region at the end terminus of TTLs regulate their activity and dynamic localization.