Abstract text: Understanding growth mechanisms in the context of global warming is essential because moderate temperature increases promote rapid growth of selective organs at the expense of storage organs, reducing yields. In Arabidopsis thaliana, temperature-induced hypocotyl elongation (TIHE) in seedlings is mediated by key molecular components, including phytochrome-interacting factors, auxin, and brassinosteroids, which collectively modulate gene expression and orchestrate TIHE. Numerous cell wall (CW)-related genes are putatively controlled by these components. Though the importance of CW modifications for growth has been extensively demonstrated in developmental models such as etiolated hypocotyls, the role of CW in TIHE remains obscure. 
We investigated the coordination between CW pectin metabolism highlighting homogalacturonan (HG) and TIHE using morphological, biochemical, and transcriptomic approaches. Our analyses revealed spatio-temporal changes in hypocotyl elongation in response to temperature, coordinated with modifications in CW and pectin, including HG metabolism. We generated the gaut10gaut11 double mutant impaired in galacturonosyltransferase (GAUT) activity and characterized its response to temperature. Homogalacturonan backbone synthesis, as well as other aspects of pectin and CW metabolism (e.g. HG substitution patterns, rhamnogalacturonan-I composition) were altered in gaut10gaut11, leading to defective TIHE. Comprehensively, these outcomes indicate that HG synthesis is required to modulate pectin and CW metabolism during TIHE.