FveTRM5 plays a critical role in regulating fruit shape in woodland strawberry

Cultivated strawberry is a globally important fruit crop with high economic value. Fruit shape contributes to fruit quality and diversity and is a target for breeding, but very few regulatory genes have been reported in strawberry. Here, we identified an ethyl methanesulfonate (EMS) round fruit (rf) mutant that produces round or flat fruits in woodland strawberry. The primary candidate point mutation is located in the second exon of FvH4_2g22810, causing a premature stop codon at residue 266. This gene encodes a protein with a high similarity to TON1 RECRUITING MOTIF 5 (TRM5) and has therefore been named FveTRM5. Transformation of FveTRM5pro:FveTRM5 into rf could rescue the round fruit phenotype, suggesting that FveTRM5 is responsible for rf. Overexpression of FveTRM5 produced elongated organs in both Arabidopsis and woodland strawberry, suggesting a conserved role in different species. FveTRM5 is ubiquitously expressed with higher levels in developing organs. Observation of cell shape showed that FveTRM5 promotes cell elongation and inhibits cell division in the medial-lateral direction in the receptacle. The FveTRM5 protein localized to microtubules. In conclusion, our results suggest that FveTRM5 plays an essential role in regulating strawberry fruit shape by influencing cell elongation and cell division, providing an excellent target gene for breeding new fruit shape cultivars.