G-protein couples MAPK cascade through maize heterotrimeric Gβ subunit

Heterotrimeric G protein G beta interacts with G gamma subunit to generate G beta y dimer in modulation of various biological processes. The modulatory events at transcriptome scale of plant G beta subunit remain largely unknown. To reveal the regulatory basis of G beta subunit at transcriptome level, we first identified a canonical maize G beta subunit MGB1 that physically interacted with Type C G gamma protein MGG4. For transcriptome analysis, two independent CRISPR/Cas9-edited MGB1 lines were generated, which all exhibited growth arrest, suggestive of MGB1 essential for maize seedling establishment. Transcriptomic outcomes showed that MGB1 knockout resulted in elevated transcriptional abundance of plant immune response marker PR and immune receptor RPM1. Integrated GO, KEGG, and GSEA analyses pinpointed the enrichment of differentially expressed genes in defense response pathway. Functional association network construction revealed MAPK cascade components and PR protein as hub regulators of MGB1-mediated immune signaling. MGB1 and scaffold protein ZmRACK1 together with MAPK cascade components coordinately modulated maize immune responses. We built a modulatory hierarchy of G beta subunit at transcriptome and interacting scales, which is informative for our understanding of the regulatory basis of G protein signaling.