OsPUP1 Modulates Cytokinin Distribution and Antioxidant Defense to Regulate Heat Stress Tolerance in Rice

Heat stress has emerged as one of the major environmental factors constraining rice growth. In our previous studies, OsPUP1, a member of the purine transporter protein family in rice, has been verified to be involved in the transport of cytokinin (CK). Unfortunately, the role of the OsPUP1 gene in the heat stress response has not been fully elucidated to date. In this study, we show that overexpression of OsPUP1, encoding a purine permease in rice, leads to severe growth inhibition and oxidative damage under heat stress. OsPUP1 overexpression lines exhibited increased accumulation of peroxides and malondialdehyde (MDA), along with significantly reduced activities of superoxide dismutase (SOD) and peroxidase (POD). Together with previous findings, these results suggest that OsPUP1 modulates CK transport, thereby influencing the spatial distribution of CK within the plant, which in turn regulates antioxidant defense mechanisms and heat stress response. This study uncovers a key role for OsPUP1 in controlling thermotolerance in rice and highlights the importance of CK distribution in plant adaptation to heat stress.