AUTHOR=Zhu Chuanmei , Liu Lei , Crowell Olivia , Zhao Hui , Brutnell Thomas P. , Jackson David , Kellogg Elizabeth A. 

TITLE=The CLV3 Homolog in Setaria viridis Selectively Controls Inflorescence Meristem Size

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.636749

DOI=10.3389/fpls.2021.636749

ISSN=1664-462X

ABSTRACT=<p>The CLAVATA pathway controls meristem size during inflorescence development in both eudicots and grasses, and is initiated by peptide ligands encoded by <italic>CLV3</italic>/<italic>ESR</italic>-related (<italic>CLE</italic>) genes. While CLV3 controls all shoot meristems in <italic>Arabidopsis</italic>, evidence from cereal grasses indicates that different meristem types are regulated by different CLE peptides. The rice peptide FON2 primarily controls the size of the floral meristem, whereas the orthologous peptides CLE7 and CLE14 in maize have their most dramatic effects on inflorescence and branch meristems, hinting at diversification among CLE responses in the grasses. <italic>Setaria viridis</italic> is more closely related to maize than to rice, so can be used to test whether the maize CLE network can be generalized to all members of subfamily Panicoideae. We used CRISPR-Cas9 in <italic>S. viridis</italic> to knock out the <italic>SvFON2</italic> gene, the closest homolog to <italic>CLV3</italic> and <italic>FON2</italic>. <italic>Svfon2</italic> mutants developed larger inflorescence meristems, as in maize, but had normal floral meristems, unlike <italic>Osfon2</italic>, suggesting a panicoid-specific CLE network. Vegetative traits such as plant height, tiller number and leaf number were not significantly different between mutant and wild type plants, but time to heading was shorter in the mutants. <italic>In situ</italic> hybridization showed strong expression of <italic>Svfon2</italic> in the inflorescence and branch meristems, consistent with the mutant phenotype. Using bioinformatic analysis, we predicted the co-expression network of <italic>SvFON2</italic> and its signaling components, which included genes known to control inflorescence architecture in maize as well as genes of unknown function. The similarity between SvFON2 function in Setaria and maize suggests that its developmental specialization in inflorescence meristem control may be shared among panicoid grasses.</p>