Functional divergence of G protein γ subunits drives plant vigor and improvement through the CPK28-PIP1;2 pathway in tomato

Maintaining robust plant vigor is essential for sustaining crop productivity, yet the precise roles and molecular underpinnings of G protein γ subunits in this process remain elusive. This study reveals that GGC1 is under selection during tomato domestication, and its mutants exhibit enhanced plant vigor, characterized by superior growth, increased yield, and improved fruit quality. In contrast, triple mutants gga1/ggb1/ggb2 display severely compromised vigor resembling slgb1 mutants lacking the Gβ subunit. Protein assays reveal that GGC1 suppresses the interaction between the three Gγ subunits (GGA1, GGB1, and GGB2) and SlGB1. Further, GGC1 inhibits calcium-dependent protein kinase 28 (CPK28)-mediated phosphorylation of aquaporin plasma membrane intrinsic protein 1;2 (PIP1;2) at the T172 site. Downstream of GGC1, both CPK28 and PIP1;2 positively regulate plant vigor by enhancing photosynthesis. These findings illuminate the functional divergence among G proteins in controlling crop vigor, offering potential strategies to engineer high-yield germplasm with enhanced CO₂ assimilation and photosynthetic efficiency.