Maize Genomics and Genetics 2025, Vol.16, No.4, 219-228 http://cropscipublisher.com/index.php/mgg 224 phosphorus from old leaves to new leaves. Of course, this transport activity is also affected by phosphorylation (Wang et al., 2020a). The situation of ZmVPE is slightly different. It enhances the release of phosphorus in the vacuoles, that is, it enables the internal Pi to re-participate in the flow, thereby helping plants maintain phosphorus balance. Another example is that after overexpression of ZmAPRG, not only did the phosphorus-related fluxes change, but also the lipid structure and photosynthetically related metabolites changed, indicating that its role under low-phosphorus conditions may be more complex than imagined. 7 Case Study 7.1 Background and selection of the target transporter gene for overexpression Not all transporters in corn are worthy of in-depth study, but ZmPT7 is an exception. This gene belonging to the PHT1 family was noticed because it has a particularly strong response when there is a phosphorus deficiency. It expresses itself both in the roots and leaves, and the reaction is very obvious. Similar genes can also be found in other plants, and their functions are quite close as well. Taking these characteristics into account, researchers selected ZmPT7 as a candidate for overexpression validation to see exactly how much it could play in phosphorus absorption and distribution. 7.2 Transformation process and verification of transgenic lines Not all experiments go smoothly, but the transformation process this time is relatively mature. Researchers used Agrobacterium-mediated methods to introduce ZmPT7 into corn and established overexpressed plants. Next, it was necessary to verify whether the conversion was successful, so PCR detection and expression analysis and other methods were used. To further confirm its function, this gene was also placed in yeast and Arabidopsis mutants. The results showed that it could indeed make up for the missing phosphorus transport function (Wang et al., 2020a). 7.3 Key findings: enhanced phosphate uptake, altered physiological traits, and potential agronomic benefits When phosphorus is insufficient, these overexpressed maize lines show particularly obvious symptoms - their phosphorus absorption capacity is much stronger than that of the control (Figure 2). What's more interesting is that they can effectively transfer the phosphorus from the old leaves to the new ones. Overall, the total phosphorus content of the plants is also higher. Its growth condition is also much better than that of the wild type. However, the matter is not that simple. The research also found that the activity of ZmPT7 is regulated by phosphorylation, indicating that its working mechanism may be more complex than expected. In summary, the overexpression of ZmPT7 is indeed helpful in enhancing phosphorus absorption and internal redistribution, and it also provides a promising direction for cultivating efficient corn varieties under low-phosphorus conditions in the future. 8 Implications for Crop Improvement and Phosphate Management 8.1 Potential applications in breeding phosphate-efficient maize varieties Not every plot of land is suitable for heavy application of phosphorus fertilizer, especially in phosphorus-deficient or alkaline soil, where conventional methods are difficult to maintain high yields. Against this backdrop, it has become particularly crucial to breed corn varieties that can efficiently utilize phosphorus. Researchers have identified many candidate genes related to phosphorus absorption and utilization (Guo et al., 2024a). If these genes can be integrated into the breeding program, it is possible to produce varieties that can have good harvests even with less fertilization. Of course, genetic improvement alone is not enough. Sometimes, using phosphorus-solubizing bacteria or mycorrhizal bacteria together, especially in problem soils, may yield better results (Adnan et al., 2020; Wahid et al., 2020; Beltran-Medina et al., 2023). 8.2 Integration with sustainable agricultural practices to reduce fertilizer dependency Excessive use of chemical fertilizers does not necessarily mean they are effective. It wastes resources and may even pollute the environment. In contrast, more precise and economical fertilization methods, such as strip fertilization, foliar spraying or local application, are more worthy of promotion (Rafiullah et al., 2020; Mussarat et al., 2021; Wang et al., 2023a). In addition, intercropping, planting cover crops, and using phosphorus-releasing microorganisms, although traditional, have obvious benefits in enhancing phosphorus efficiency and improving soil quality (Pavinato et al., 2017; Song et al., 2021). Interestingly, some studies conducted simulation tests, and
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