Plant Gene and Trait 2025, Vol.16, No.3, 92-103 http://genbreedpublisher.com/index.php/pgt 96 expression is not only related to the fluctuation of sugar concentration, but also to the efficiency of photosynthesis. This shows that it may be both a “sensor” and a “regulator”. In fact, it is not just sugarcane. Studies on other plants have also found that when the gene expression of Calvin cycle enzymes such as PRK and Rubisco changes, not only photosynthesis is affected, but also the synthesis of starch and even lipids will change (Deslandes-Hérold et al., 2022). This kind of discovery makes people realize that if you want to increase the sugar yield of sugarcane, external management alone is not enough, and you have to start from the perspective of regulating key genes. Figure 2 Simplified model of the Calvin-Benson cycle reactions (Adopted from Chen et al., 2022) 5 Integration of Light Reaction and Carbon Metabolism 5.1 Coordination between photosystem function and CO₂ assimilation In photosynthesis, the light reaction and carbon fixation are not independent of each other. For crops with high light efficiency like sugarcane, the activity of the photosystem and the absorption of carbon dioxide need to be properly coordinated. One cannot run too fast and the other cannot keep up. LHC, or light-harvesting complex, is like installing a “light-enhancing mirror” on the photosystem, which greatly expands the light-harvesting range. With more light energy, there is “power” to fix more carbon dioxide. Especially PSII (photosystem II), whether the structural organization between it and LHC is reasonable directly determines whether the light energy is transmitted smoothly and whether it can be used efficiently. It is not surprising to capture a lot of energy. The key is whether it can be used steadily and turned quickly. This is the fundamental factor affecting the efficiency of carbon fixation (Müh and Zouni, 2020; Lokstein et al., 2021). 5.2 Regulation of photoprotection mechanisms under fluctuating light The light in nature is not as stable as that in the laboratory. When sugarcane is exposed to the sun in the field, the light intensity changes suddenly. If you are not careful, there will be too much energy to use, which will become a problem. At this time, it is not enough to absorb light desperately, but there must be a way to “release the flood”. NPQ (non-photochemical quenching) is like a set of “exothermic valves”, which converts excess light energy into heat and discharges it, protecting PSII from oxidation damage. PsbS protein plays the role of “reactor” here, helping plants to quickly adjust their sensitivity to light (Liu et al., 2019). In addition to it, phosphorylation of LHCII protein and structural changes of thylakoid membrane are also part of the system - together they make the
RkJQdWJsaXNoZXIy MjQ4ODYzNA==