NERD1, a novel regulator of ovule number in Arabidopsis (PLOS Genetics)

Seed number is a critical component of crop yield; the number of ovules determines the number of seeds. Ovule initiation in the carpel margin meristem (CMM) is controlled by genetic (i.e., AINTEGUMENTA, LEUNIG, SEUSS) and hormonal factors (auxins, cytokinins, gibberellins, and brassinosteroids). Most of the mutants affected in ovule number have also defects in other tissues. In this study, Yuan and Kessler wanted to identify actors that could regulate ovule number without affecting other tissues. The authors exploited natural variation in ovule number in 189 Arabidopsis accessions. They conducted a Genome Wide Association Study (GWAS) and identified some genomic regions linked to variation in ovule number. Then they focused in the genes containing the most significantly associated SNPs and analyzed mutants for those genes. Insertional lines for the NEW ENHANCER of ROOT DWARFISM (NERD1) gene showed reduced ovule number, ovule defects, and other male defects; while overexpression of NERD1 in the Altair-5 background (a low number accession) increased ovule number. Interestingly, the NERD1 gene is expressed ubiquitously during Arabidopsis development; the NERD1 is predicted to be a membrane protein. Further work is required to establish at which level NERD1 interacts with the pathways controlling ovule initiation. This research extends our knowledge of how ovule number (and hence seed number) could be increased. (Summary by Humberto Herrera-Ubaldo) PLOS Genetics 10.1371/journal.pgen.1007934