G-protein couples MAPK cascade through maize heterotrimeric Gß subunit.

ABSTRACT

KEY MESSAGE G protein couples MAPK cascade through maize heterotrimeric Gß subunit MGB1. Heterotrimeric G protein Gß interacts with Gγ subunit to generate Gßγ dimer in modulation of various biological processes. The modulatory events at transcriptome scale of plant Gß subunit remain largely unknown. To reveal the regulatory basis of Gß subunit at transcriptome level, we first identified a canonical maize Gß subunit MGB1 that physically interacted with Type C Gγ 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 Gß subunit at transcriptome and interacting scales, which is informative for our understanding of the regulatory basis of G protein signaling.