The maize heterotrimeric G protein β subunit controls shoot meristem development and immune responses

Abstract Heterotrimeric G-proteins are important transducers of receptor signaling, functioning in plants with CLAVATA receptors in control of shoot meristem size, and with pathogen associated molecular pattern (PAMP) receptors in basal immunity. However, whether specific members of the heterotrimeric complex potentiate crosstalk between development and defense, and the extent to which these functions are conserved across species, has not been addressed. Here we used CRISPR/Cas9 to knockout the maize Gβ subunit gene, and found that the mutants were lethal, differing from Arabidopsis, where homologous mutants have normal growth and fertility. We show that lethality is not caused by a specific developmental arrest, but by autoimmunity. We used a genetic diversity screen to suppress the lethal gβ phenotype, and also identified a new maize Gβ allele with weak autoimmune responses but strong development phenotypes. Using these tools, we show that Gβ controls meristem size in maize, acting epistatically with Gα , suggesting that Gβ and Gα function in a common signaling complex. Furthermore, we used an association study to show that natural variation in Gβ influences maize kernel row number, an important agronomic trait. Our results demonstrate the dual role of Gβ in immunity and development in a cereal crop, and suggest that it functions in crosstalk between these competing signaling networks. Therefore, modification of Gβ has the potential to optimize the tradeoff between growth and defense signaling to improve agronomic production. Significance Cereal crops, such as maize provide our major food and feed. Crop productivity has been significantly improved by selection of favorable architecture and development alleles, however crops are constantly under attack from pathogens, which severely limits yield due to a defense-growth tradeoff. Therefore, it is critical to identify key signaling regulators that control both developmental and immune signaling, to provide basic knowledge to maximize productivity. This work shows that the maize G protein β subunit regulates both meristem development and immune signaling, and suggests that manipulation of this gene has the potential to optimize the tradeoff between yield and disease resistance to improve crop yields.