LEAFY interacts with WHEAT ORTHOLOG OF APO1 to regulate spikelet number per spike in wheat

Abstract

AbstractIn wheat, the transition of the inflorescence meristem (IM) to a terminal spikelet determines the spikelet number per spike (SNS) and the maximum number of grains. In this study, we demonstrate that this transition is repressed by the plant-specific transcription factorLEAFY(LFY) and promoted by the MADS-box genesVRN1andFUL2, affecting SNS in opposite directions. LFY physically interacts with WHEAT ORTHOLOG OF APO1 (WAPO1), and loss-of-function mutations in either or both genes result in significant and similar reductions in SNS. These results indicate that both genes are required to maintain IM indeterminacy. The spatio-temporal distribution of these genes during spike development characterized by single-molecule fluorescencein-situhybridization provides insights on their roles in spike and spikelet development. Finally, we identify naturalLFY-Balleles that affect SNS, determine their interactions with natural alleles ofWAPO-A1, and select an allele combination that maximizes SNS for wheat improvement.Summary StatementThe transcription factorLEAFYplays a central role in the regulation of the number of spikelets per spike in wheat.