Elevated [CO2] alleviates AsGH3.8-mediated stolon growth inhibition via IAA accumulation and soluble sugar reduction in perennial grass

Rapid stolon growth is advantageous for greater turf density and faster establishment. Elevated CO 2 concentration ([CO 2 ]) can stimulate stolon growth by increasing the levels of auxin indole-3-acetic acid (IAA) in stolon nodes and internodes of stoloniferous creeping bentgrass ( Agrostis stolonifera ). Concurrently, the expression of the auxin-binding gene AsGH3.8 is significantly upregulated by elevated [CO 2 ]. However, the role of auxin-binding gene AsGH3.8 in stolon growth under elevated [CO 2 ] was still unclear. The objective of this study was to investigate the mechanism by which AsGH3.8 mediates elevated [CO 2 ]-induced plant growth in creeping bentgrass. Transgenic and wild-type plants were grown in growth chambers under ambient [CO 2 ] (400 ± 10 μmol⋅mol −1 ) or elevated [CO 2 ] (800 ± 10 μmol⋅mol −1 ). Overexpression of AsGH3.8 significantly inhibited the stolon growth, as shown by the decline in stolon internode number and length. Elevated [CO 2 ] could mitigate the inhibitory effects of AsGH3.8 overexpression on the stolon growth of creeping bentgrass through increasing IAA and decreasing soluble sugar content in stolons of creeping bentgrass. This study provides new insights into the physiological mechanisms underlying AsGH3.8 -mediated plant growth under elevated [CO 2 ]. • Overexpression of auxin-binding gene AsGH3.8 significantly inhibited the growth of creeping bentgrass. • Elevated [CO 2 ] could mitigate the inhibitory effects of AsGH3.8 overexpression on the growth of creeping bentgrass. • This recovery is driven by a transcriptional reprogramming of auxin metabolism, leading to the enhanced IAA accumulation. • Elevated [CO 2 ] regulates carbon partitioning by down-regulating the sucrose synthesis gene AsSUS1 , reducing the total soluble sugar content.