Divergence in the effects of sugar feedback regulation on the major gene regulatory network and metabolism of photosynthesis in leaves between the two founding Saccharum species

Sugarcane is a crop that accumulates sucrose with high photosynthesis efficiency. Therefore, the feedback regulation of sucrose on photosynthesis is crucial for improving sugarcane yield. Saccharum spontaneum and Saccharum officinarum are the two founding Saccharum species for modern sugarcane hybrids. S. spontaneum exhibits a higher net photosynthetic rate but lower sucrose content than S. officinarum. However, the mechanism underlying the negative feedback regulation of photosynthesis by sucrose remains poorly understood. This study investigates the effects of exogenous sucrose treatment on S. spontaneum and S. officinarum. Exogenous sucrose treatment increases sucrose content in the leaf base but inhibits photosynthetic efficiency and the expression of photosynthesis-related pathways (including RBCS and PEPC) in both species. However, gene expression patterns differed significantly, with few differentially expressed genes (DEGs) shared between the two species, indicating a differential response to exogenous sucrose. DEGs involved in the pentose phosphate pathway, sulfur metabolism, and alanine, aspartate, and glutamate metabolism were uniquely enriched in S. spontaneum, potentially contributing to the differential changes in sucrose content in the tip between the two species. Additionally, the expression networks of PEPC and RBCS displayed divergence between the two species. We propose a model of the mechanisms underlying the negative feedback regulation of photosynthesis by sucrose in the leaves of S. spontaneum and S. officinarum. Our findings enhance the understanding of sucrose feedback regulation on photosynthesis and highlight the metabolic and gene expression differences between S. spontaneum and S. officinarum