Legume Genomics and Genetics 2025, Vol.16, No.1, 33-43 http://cropscipublisher.com/index.php/lgg 35 chloroplasts. Interestingly, this housekeeper is quite sensitive. When encountering troubles such as heavy metal pollution, its working condition will change accordingly. This indicates that it is not only a butler, but also part-time as a security guard, helping soybeans cope with various environmental pressures. Simply put, GmGLK1 is an all-around player who not only ensures the normal functioning of chloroplasts, but also helps plants overcome difficulties. 3.3 GmPIF4: modulating photosynthetic adaptation to environmental stress It's quite tricky for soybeans to encounter strong light, but there is a transcription factor called GmPIF4 that works quite well. This thing is quite interesting. It not only deals with photosynthesis, but also has to worry about not accumulating too much reactive oxygen species (ROS). Simply put, when the sunlight is too strong, GmPIF4 acts as a dispatcher, adjusting the expression of stress response genes (Zhang et al., 2023). Interestingly, it can also cooperate with proteins such as GmVTC2, one responsible for enhancing ROS scavenging ability and the other maintaining photosynthetic efficiency (Figure 1). However, speaking of which, this regulatory mechanism is not omnipotent, but it has indeed been of great help in dealing with fluctuating light environments, allowing plants to recover faster. 4 Mechanisms of Gene Regulation in Photosynthesis 4.1 Transcriptional regulation by light-responsive genes Soybeans are a very interesting crop, as their photosynthesis completely follows light. Speaking of this, we have to mention the GmRPI2 gene - this guy encodes ribose-5-phosphate isomerase, which plays an important role in photosynthesis. In fact, its promoter region is particularly sensitive, and the photoresponsive elements inside are like switches (Sun et al., 2023). Experiments have shown that if this gene is overexpressed, the photosynthetic capacity of soybeans can indeed be improved. Not only do the leaves become greener, but the photosynthetic rate and sugar content also increase. But when it comes to photosynthesis, it also involves other genes, such as GmRCAα, which is responsible for Rubisco activating enzyme. Interestingly, it relies on transcription factors such as bZIP to initiate, and these proteins directly bind to its promoter region (Zhang et al., 2016). To put it simply, the soybean photosynthesis system is a precise sunlight sensor, with each link adjusting its working state according to changes in light. 4.2 Post-transcriptional regulation through RNA-binding proteins In fact, there is another way to deal with soybean photosynthesis - post transcriptional regulation is also crucial. Those RNA binding proteins (RBPs) act as quality inspectors, specifically targeting the mRNAs involved in photosynthesis (Ku et al., 2022). Take GmZF392 protein as an example, it belongs to the CCCH zinc finger protein family and works in a unique way: it directly runs to the promoter region of the target gene and "codes" with specific cis elements (Lu et al., 2021). By doing this, mRNAs not only became more stable, but also improved translation efficiency, ultimately leading to an increase in oil content in soybean seeds. Simply put, this mechanism is to give the green light to photosynthesis related mRNAs, ensuring that they can smoothly transform into proteins and accurately find their job positions. 4.3 Post-translational modifications in photosynthetic enzymes In the matter of photosynthesis in soybeans, protein modification (PTMs) actually secretly controls many key links. Just take GmDREB2A; For this protein, there is a region with a particularly high amount of serine/threonine on it, like an emergency braking device - as long as this region remains, the protein activity is suppressed (Mizoi et al., 2012). But in the event of drought or something like that, once this braking device is removed, the protein immediately becomes energetic. Not only does it become more stable itself, but it can also help enhance the stress resistance and photosynthetic efficiency of soybeans. Another interesting example is GmGATA58, a transcription factor specifically responsible for chlorophyll synthesis. However, it also has to act according to the PTMs. These modifications are like patching proteins, directly determining its activity and lifespan (Zhang et al., 2020a). To put it bluntly, the photosynthetic system of soybeans is like a precise mechanical watch, and these post-translation modifications are the masters who fine-tune the gears. A slight twist can change the accuracy of the entire watch's timekeeping.
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