qPSR10 positively regulates pectin demethylesterification and cold tolerance in rice

A low degree of methylesterification (DM) of pectin is critical for regulation of plant growth and to enhance abiotic stress tolerance. The DM of Pectin is regulated by pectin methylesterase (PME) and the enzymatic activity of PME is inhibited by pectin methylesterase inhibitor (PMEI). However, the mechanisms of PME and PMEI regulation in rice are poorly understood. In this study, qPSR10 was identified as a crucial regulator of the DM of pectin in rice. The serine-to-glycine substitution at amino acid position 115 (S115G) of qPSR10 affects the DM of pectin and its interaction with OsPME25 and OsPMEI28. qPSR10G interacts with the PRO domain of OsPME25, which enhances PME activity and decreases the DM of pectin. qPSR10 is also able to interact with, and promotes the ubiquitination degradation of, OsPMEI28, which indirectly increases PME activity and decreases the DM of pectin. In addition, a lower DM of pectin promotes the expression of critical genes in the cold tolerance-related MAPK signaling pathway, thereby improving rice cold tolerance. This research improves our understanding of the molecular regulatory mechanism of the DM of pectin in rice, and provides genetic resources and theoretical support for molecular design breeding of rice.