FRUITFULL is involved in double fruit formation at high temperature in sweet cherry

Abstract

Sweet cherry (Prunus avium L.) is sensitive to high temperature during pistil development, but the spatial and temporal variability of high temperature and the molecular mechanism of its impact on the formation of double pistils are little known. An analysis of historical and projected climate data was conducted to characterize the spatial and temporal variability of high temperature from June to September at 5 stations in main sweet cherry growing regions of China and a warmer reference site. Several high temperature indices were developed to quantify heat frequency, intensity and duration during pistil development based on observed and projected maximum temperatures. The risk of high temperature was projected to increase under two Representative Concentration Pathways for 2035–2065 and 2070–2100, and the increasing rate was higher in the south station than the north except for Yantai city. Furthermore, to explore the mechanism of double fruit formation at high temperature, we investigated the regulation of FRUITFULL (FUL) during the growth of floral buds in sweet cherry. We identified a AP1/ FUL family gene FUL from sweet cherry, which was grouped with PpCAL, PpMADS6 from Prunus persica, ParFUL from Prunus armeniaca, PyeCAL from Prunus yedoensis, and PdCAL, PdAGL8 from Prunus dulcis by phylogenetic tree analysis. The seasonal expression level of PavFUL was higher in the high multi-pistil rate cultivar during summer stage and enhanced by high temperature. Moreover, overexpression of PavFUL led to multi-silique formation and early flowering in Arabidopsis. In addition, Y2H and BiFC assays revealed that PavFUL interacted with other MADS-box proteins, including PavLFY, PavSOC1, PavAP1, and PavSEP, to co-regulate the flowering and multi-silique formation. Our findings will help decipher the possible mechanism of high temperature-mediated double fruit via affecting FUL and other MADS-box genes in molecular level for tree fruit species.