PpPKp1 Coordinates Growth and Cold Tolerance by Integrating Energy‐Cytokinin Signalling via Pyruvate Metabolism in Poa pratensis

Plastidial pyruvate kinase (PKp; EC 2.7.1.40), as a core enzyme regulating plant carbon metabolism, has been confirmed to be a key component in plant stress response. However, the specific regulatory network in cold response and the molecular mechanism mediating cold tolerance remain elusive. This study reveals that the expression of PpPKp1, a chloroplast-localized plastid pyruvate kinase gene from Poa pratensis var. anceps cv. Qinghai, is significantly induced by low temperature and drought stress. Overexpression of PpPKp1 in Arabidopsis thaliana and Poa pratensis enhanced pyruvate kinase activity and pyruvate content, thereby improving tillering capacity and biomass accumulation under cold conditions, while also promoting root elongation, shoot growth, and maintaining the relative stability of ROS. Conversely, RNAi-mediated suppression of PpPKp1 in P. pratensis elicited contrasting phenotypes and physiological responses. Mechanistic investigations demonstrated that under cold stress, PpPKp1 facilitates energy supply by enhancing glycolytic/TCA cycle flux and simultaneously coordinates arginine biosynthesis with cytokinin signalling transduction. This integrated mechanism of 'energy provision-metabolite synthesis-signal regulation' is closely associated with the maintenance of plant growth and development under cold conditions, balancing resource allocation between stress resistance and growth. Ultimately, it leads to significantly enhanced cold tolerance. Our work unveils for the first time the molecular mechanism by which PpPKp1 regulates plant cold responses through coupling central carbon metabolism and hormone signalling. It provides novel insights into the synergistic network of 'plastid metabolism-systemic stress resistance' in plants, and offers candidate genes and a theoretical basis for the genetic improvement of cold tolerance in crops.