Gibberellin and the miRNA156-targetedSlSBPssynergistically regulate tomato floral meristem activity and fruit patterning

Abstract

ABSTRACTMany developmental processes associated with fruit development take place at the floral meristem (FM). Age-regulated microRNA156 (miR156) and gibberellins (GA) interact to control flowering time, but their interplay in subsequent stages of reproductive development is poorly understood. Here, we show that GA and miR156 function in tomato FM and fruit patterning. High GA responses or overexpression of miR156 (156OE), which leads to low levels of miR156-targetedSQUAMOSA PROMOTER BINDING PROTEIN– LIKE(SPL/SBP), resulted in enlarged FMs, defects in FM determinacy and fruits with increased locule number. Conversely, low GA responses reduced fruit indeterminacy and locule number, and overexpression of a miR156-resistantSlSBP15allele (rSBP15) reduced cell number and size in the FM, as well as locule number. GA responses were partially required for the fruit defects observed in 156OE andrSBP15plants. Transcriptome analysis and genetic interactions revealed shared and divergent functions of miR156-targetedSlSBPs, PROCERA/DELLAand the classicalWUSCHEL/CLAVATApathway, which has been previously associated with meristem size and determinacy. Our findings reveal that the miR156/SlSBP/GA regulatory module is deployed differently depending on developmental stage and create novel opportunities to genetically fine-tune aspects of fruit development that have been important for tomato domestication.