Counteractive Effects of Sugar and Strigolactone on Leaf Senescence of Rice in Darkness

Plant hormones strigolactones (SLs) were recently reported to induce leaf senescence. It was reported that sugar suppresses SL-induced leaf senescence in the dark; however, the mechanism of the crosstalk between SLs and the sugar signal in leaf senescence remains elusive. To understand this mechanism, we studied the effects of glucose (Glc) on various senescence-related parameters in leaves of the rice. We found that sugars alleviated SL-induced leaf senescence under dark conditions, and the co-treatment with Glc suppressed SL-induced hydrogen peroxide generation and membrane deterioration. It also suppressed the expression levels of antioxidant enzyme genes upregulated by SL, suggesting that Glc alleviates SL-induced senescence by inhibiting the oxidative processes. SLs can adapt to nutrient deficiency, a major factor of leaf senescence; therefore, we suggest the possibility that Glc and SL monitor the nutrient status in plants to regulate leaf senescence.