Source-sink coordination serves as the foundation for improving crop yield. Current research primarily focuses on individual factors, such as increasing the source or expanding the sink, which often leads to disrupted source-sink balance, causing trade-offs among photosynthesis, yield, and stress response. To address these limitations, we present an integrated synthetic biological framework that synergistically enhances photosynthetic efficiency (source capacity), sink optimization, and abiotic stress tolerance. We developed an editing-overexpression coupling (EOC) vector system enabling simultaneous overexpression of four photosynthesis-enhancing genes (Cyt c₆, PsbA, FBPase, OsMGT3), knockout of three yield-limiting genes (GS3, Gn1a, OsAAP5), and self-excision of selection markers, gene-editing modules, and fragment deletion cassettes. Field evaluations of CFMP-gga transgenic lines revealed significant physiological improvements, including 13%–17% increase in photosynthetic rates, improved chlorophyll fluorescence parameters, and increased stomatal conductance. These enhancements translated into remarkable agronomic gains, including 18.7%–22.3% higher grain yield, 23.1%–26.1% increased biomass, and improved panicle architecture (increased grain size and grain number per panicle). The engineered lines maintained superior thermotolerance (under 42 °C stress) and alkali tolerance (at pH 10) compared to wild-type controls. This study provides a strategy for enhancing crop yield by demonstrating that coordinated multi-gene regulation of source-sink dynamics, coupled with stress resilience engineering, achieves concurrent improvements.

Chloroplasts are the center of plant life activities including photosynthesis, growth and development, and abiotic stress response. Chloroplast development and biogenesis in rice have been studied in detail, but how does abiotic stress affect chloroplasts is less studied. We obtained an albino mutant, alm1, whose chlorophyll content was greatly decreased. Transmission electron microscopy showed that chloroplast development in alm1 was blocked, especially in thylakoid-like structures, which could not form normally. The ALM1 gene encodes a chloroplast-localized superoxide dismutase. Full-length ALM1 successfully restored the non-albino phenotype, and in knockout lines, the albino phenotype reappeared. The ALM1 gene is expressed mainly in young leaves. alm1 plants died as a consequence of excessive reactive oxygen accumulation after the third-leaf stage. A series of biochemical assays verified that ALM1 interacted with the OsTrxz protein, which is one of the components of plastid-encoded RNA polymerase (PEP) complexes. A western blot experiment indicated that ALM1 played an important role in stabilizing OsTrxz in rice. An overexpression test of ALM1 revealed that ALM1 can increase drought resistance by removing excess reactive oxygen in rice seedlings. This study suggests that ALM1 not only participates in rice chloroplast biogenesis, but also increases rice stress resistance by scavenging excess reactive oxygen.

Abiotic stresses such as drought, salinity, and low temperature cause–losses in rice production worldwide. The emergence of transgenic technology has enabled improvements in the drought resistance of rice plants and helped avert crop damage due to drought stress. Selectable marker genes conferring resistance to antibiotics or herbicides have been widely used to identify genetically modified plants. However, the use of such markers has limited the public acceptance of genetically modified organisms. Marker-free materials (i.e., those containing a single foreign gene) may be more easily accepted by the public and more likely to find common use. In the present study, we created marker-free drought-tolerant transgenic rice plants using particle bombardment. Overall, 842 T₀ plants overexpressing the rice ascorbate peroxidase-coding gene OsAPX2 were generated. Eight independent marker-free lines were identified from T₁ seedlings using the polymerase chain reaction. The molecular characteristics of these lines were examined, including the expression level, copy number, and flanking sequences of OsAPX2, in the T₂ progeny. A simulated drought test using polyethylene glycol and a drought-tolerance test of seedlings confirmed that the marker-free lines carrying OsAPX2 showed significantly improved drought tolerance in seedlings. In the field, the yield of the wild-type plant decreased by 60% under drought conditions compared with normal conditions. However, the transgenic line showed a yield loss of approximately 26%. The results demonstrated that marker-free transgenic lines significantly improved grain yield under drought-stressed conditions.