<i>WUSCHEL-D1</i> upregulation enhances grain number by inducing formation of multiovary-producing florets in wheat.

Abstract

Innovative genetic improvements in food crops are needed to maintain global food security. Here, we report the map-based cloning of <i>TaWUSCHEL-D1</i> (<i>WUS-D1</i>) as the gene responsible for the multiovary phenotype in wheat, which produces three fertile ovaries and grains per floret. We generated a 14.5 Gbp chromosome-level assembly of multiovary wheat line "MOV" that shows unique structural variation in the <i>Mov-1</i> physical region, resulting in widespread gene upregulation. High-resolution genetic mapping refined the locus to a 135 kbp region that contains two genes. We used nine independent deletion mutants, eight TILLING mutants, and genetic complementation of these genotypes to show that a <i>WUSCHEL</i> ortholog, <i>WUS-D1</i>, is the causal gene of the <i>Mov-1</i> locus. Expression studies showed that <i>WUS-D1</i> is highly expressed during early inflorescence development in MOV, whereas the gene is inactive in wild-type wheat. The higher <i>WUS-D1</i> expression is associated with the formation of larger meristems and floret primordia that are competent to produce multiple ovaries. These insights provide a foundation to manipulate floral organ numbers to enhance breeding capabilities of bread wheat.