Improvement of photosynthetic efficiency and yield of upland cotton by SiFBA4 gene of Saussurea involucrata

Cotton ( Gossypium hirsutum ), a key fiber crop, plays a vital role in the development of the agricultural and textile industries. Recognizing that photosynthesis contributes to approximately 95 % of crop yield, enhancing its efficiency is crucial for improving crop yield. One approach targets key regulatory enzymes, such as Fructose-1,6-bisphosphate aldolase (FBA), which is known for its role in the Calvin cycle. After introducing the SiFBA4 gene from Saussurea involucrata into cotton, we investigated how this gene influences photosynthetic characteristics, agronomic traits, yield, and fiber quality, and elucidated the mechanisms using transcriptomic and metabolomic analyses. The analysis showed significant improvements in transgenic lines compared to the wild type. There was a 17.47 % increase in the net photosynthetic rate and a 19.22 % increase in seed cotton yield. We observed an increase in the number of fruit branches and bolls, although the fiber length and strength decreased. Metabolomic analysis revealed reduced sugar content in transgenic leaves and increased sugar content in roots. Transcriptomic analysis showed the upregulation of genes encoding Calvin cycle enzymes, the chloroplast electron transport chain (PSⅠ, Cytb6/f, and PSⅡ), chlorophyll synthesis, and sugar transporters. SiFBA4 enhanced photosynthetic efficiency by increasing Calvin cycle enzyme activity and light reaction-related gene expression. It improves photosynthetic product distribution by promoting sugar transporter gene expression and increasing yield. These findings demonstrate SiFBA4 's role in regulating photosynthesis and yield formation, provide genetic resources for cotton breeding, and offer a basis for designing crop carbon assimilation and distribution networks. • SiFBA4 significantly increased photosynthetic efficiency and yield of cotton. • SiFBA4 regulates cotton growth by modulating carbon metabolism pathways. • SiFBA4 optimized the allocation of photosynthate from the source to the sink.