Expression Profiling of Four Mango FT/TFL1-Encoding Genes under Different Fruit Load Conditions, and Their Involvement in Flowering Regulation.

Plant flowering is antagonistically modulated by similar FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1) proteins. In mango ( L.), flowering is induced by cold temperatures, unless the tree is juvenile or the adult tree had a high fruit load (HFL) in the summer. Here, we studied the effects of juvenility and fruit load on the expression of four / genes cloned from the mango 'Shelly' cultivar. Ectopic expression of in resulted in early flowering, whereas over-expression of and the two cloned genes repressed flowering. Moreover, juvenility was positively correlated with higher transcript levels of and both s. In trees with a low fruit load, leaf expression increased in winter, whereas HFL delayed its upregulation. expression was upregulated in both leaves and buds under both fruit load conditions. Downregulation of both s in buds was associated with a decrease in regional temperatures under both conditions; nevertheless, HFL delayed the decrease in their accumulation. Our results suggest that cold temperature has opposite effects on the expression of and the s, thereby inducing flowering, whereas HFL represses flowering by both suppressing upregulation and delaying downregulation. The apparent flowering-inhibitory functions of are discussed.