Abstract
Background: Pi (inorganic phosphate) is an essential mineral nutrient and a key limiting factor for plant growth. Environmental factors of carbon and energy status provided by sucrose influence plant growth and stress adaption; however, the mechanisms by which plant seedlings cope with Pi-starvation stress in conjunction with these factors remain largely unknown. Results: This study investigates the interplay between sucrose status and Pi-starvation response using a combined Pi/sucrose treatment. Through comparative transcriptomic and physiological analyses, we demonstrated that: (1) the upregulation of anthocyanin biosynthesis under Pi-starvation is significantly attenuated under sucrose deficiency, coinciding with reduced anthocyanin and ROS (reactive oxygen species) accumulation; (2) photosynthesis is downregulated under Pi-starvation with sufficient sucrose supply but upregulated under sucrose limitation, with chlorophyll content decreasing under sufficient sucrose supply and increasing under deficiency; (3) ATP-consuming anabolic pathways are downregulated under Pi-starvation with sufficient sucrose supply but showed no significant changes under sucrose deficiency; and (4) plant-pathogen interaction pathways, typically upregulated during Pi-starvation, are downregulated under insufficient sucrose supply. Additionally, we identified PIF3 (phytochrome-interacting factor 3) as a potential regulator of Pi-starvation responses, with loss-of-function mutants exhibiting retarded growth and gain-of-function mutants showing enhanced growth under Pi-starvation. Conclusion: These results highlight the critical role of sucrose status in modulating plant Pi-starvation response and provide new insights into the adaptive mechanisms by which plants coordinate C/Pi balance to cope with nutrient stress, thus extending and complementing previous research on Pi-starvation response mechanisms.