Increasing crop yield relies crucially on a holistic understanding of plant growth, which results from the combined action among metabolism, water/nutrient availability, cellular and development programs. These elements will collectively govern the balance among carbon (C) assimilation, allocation and usage during the diel cycle as well as along developmental stages. Plant cell walls represent the largest sink for photosynthetically fixed C and allocation into cell wall synthesis must be carefully controlled for optimal growth. Recently, compelling evidence has emerged that C status is able to regulate cellulose synthesis in the model plant Arabidopsis during vegetative growth, but the mechanisms remain unclear. There is a complex signalling network able to sense C levels and energy status, and integrate them into growth and development involving two antagonist kinases. The "Target of rapamycin" (TOR) signals high C availability and stimulates protein translation and growth, whereas the "Snf1-related protein kinase-1" (SnRK1) inhibits growth at low C and energy supply. The activity of both kinases is modulated by sugars, with glucose activating TOR and trehalose-6-phosphate (Tre6P), intermediate of trehalose synthesis, inhibiting SnRK1. Tre6P is not only an essential metabolite in plants, but also a sensor of sucrose status that affects metabolism at multiple levels. Sugar signaling pathways also interact with microRNAs to regulate plant development. Taken together, these information point out the importance of studying sugar signaling mechanisms in order to ameliorate plant growth and biomass accumulation, which are crucial elements for bioenergy. The present project aims to investigate the relationship among gene expression, metabolites and sugar signaling pathways (TOR, SnRK1, Tre6P) in sugarcane.
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