Journal of Energy Bioscience 2025, Vol.16, No.5, 248-262 http://bioscipublisher.com/index.php/jeb 252 4.4 Feedback regulation and sugar perception Hexokinase (HXK) is a major glucose receptor that regulates metabolism and growth. Systems such as SnRK1, TOR and T6P are jointly involved in glucose signaling and interact with hormone and environmental responses (Rolland et al., 2006; Sheen, 2016; Li et al., 2021; Stephen et al., 2021; Li and Zhao, 2024). When sugar levels are high, plants reduce their photosynthetic rate. When sugar is insufficient, the energy-saving mechanism is activated (Rolland et al., 2006; Smeekens and Hellmann, 2014; Stephen et al., 2021). Sugar signaling also interacts with nutritional and hormonal signaling to help plants adapt to the environment, but the overall mechanism remains to be further studied (Sakr et al., 2018). 5 Sugar Signaling and Plant Development: Pathways, Hormone Interactions and Developmental Outcomes 5.1 Glucose sensing pathways (dependent on hexokinase pathways and trehalose 6-phosphate signaling pathways) Plants can "sense" sugar in various ways and thereby regulate their growth. The most common one is the sensing pathway dependent on hexokinase (HXK). HXK can recognize glucose and convert it into glucose-6-phosphate. At the same time, it can also act as a signaling molecule and play a regulatory role in cells. When there is a relatively high amount of glucose in plants, HXK can inhibit the expression of genes related to photosynthesis and also affect the activity of some transcription factors, thereby altering cell division and organ formation. The HXK pathway also affects plant hormones, such as regulating the transport and response processes of auxin (Avonce et al., 2005; Rolland et al., 2006; Ciereszko, 2018; Vanderwall and Gendron, 2023). Another important pathway is related to trehalose 6-phosphate (T6P). T6P is closely related to sucrose metabolism. It is synthesized by trehalose 6-phosphate synthase and reflects the level of sucrose in cells. When T6P is abundant, the plants grow well. When T6P is low, the growth of plants will slow down. T6P functions by inhibiting SnRK1, a protein kinase. SnRK1 will limit its growth when there is insufficient energy. It can be said that the T6P-SNRK1 system acts like a "switch", linking sugar levels with processes such as plant flowering, embryonic development, and branch formation. If plants cannot synthesize T6P, such as tps1 mutants, growth disorders will occur (Avonce et al., 2005; Xing et al., 2015; Fichtner and Lunn, 2021; Wang et al., 2021b; Gobel and Fichtner, 2023). 5.2 Interaction between glucose signaling and plant hormones (ABA, auxin, cytokinin) The relationship between sugar signals and plant hormones is very close. They will affect each other's content, transportation and function. Glucose can regulate the ability of plants to synthesize and distribute auxin. Through the action of HXK, sugar can promote the synthesis of auxin and activate related genes. In turn, auxin can regulate the utilization and transportation of sugar, thus forming a feedback loop. This interaction is particularly important for the formation of roots and stems because they both control cell division and organ growth (Ciereszko, 2018; Robert, 2019; Kotov, Kotova and Romanov, 2021; Mishra et al., 2021; Rashid et al., 2022). Sugar and cytokinin also interact to jointly regulate the development of stems, roots, seeds and flowers. They can all control the activity of meristem and the growth of organs. At different growth stages, they may promote each other or inhibit each other. Abscisic acid (ABA) is often associated with stress responses and dormancy, but it is also influenced by sugar signaling. When sugar is low, SnRK1 is activated, which initiates the expression of ABA-related genes, thereby linking the state of carbon hunger with the stress response and slow growth of plants (Liu, Offler and Ruan, 2013; Xing et al., 2015; Ciereszko, 2018; Wang et al., 2021b). 5.3 Effects on flowering, seed development and fruit ripening When plants shift from vegetative growth to reproductive growth, sucrose and T6P are key signals. Before many plants are about to flower, the level of sucrose in the apical meristem will increase, thereby promoting the formation of flowers. External supplementation of sucrose can also make plants flower earlier. T6P is downstream of the sucrose signaling pathway and can activate genes such as FLOWERING LOCUS T (FT) to help plants
RkJQdWJsaXNoZXIy MjQ4ODYzNA==