The MADS-box gene RhAGL6 plays a master role in regulating the receptacle malformation in rose at low temperature

Low temperature usually results in the developmental deformity of flower organs, immensely affecting the quality of rose flowers. However, it's largely unknown about the regulatory mechanisms activated by low temperature. Here, we used a low temperature-sensitive Rosa hybrida cv. ‘Peach Avalanche’ to screen a MADS-box gene RhAGL6 via conjoint analysis between RNA sequencing (RNA-seq) and whole-genome bisulfite sequencing (WGBS). Furthermore, we found that low temperature induced the hypermethylation and elevated histone 3 lys-27 trimethylation (H3K27me3) level on the RhAGL6 promoter, leading to decreased RhAGL6 expression. In addition, RhAGL6 silencing resulted in the formation of abnormal receptacles. We also found that the levels of gibberellins (GA₃) and abscisic acid (ABA) in the receptacle under low temperature were lower and higher, respectively, than under normal temperature. Promoter activity analysis revealed that GA₃ significantly activated RhAGL6 promoter activity, whereas ABA inhibited it. Thus, we propose that RhAGL6 regulates rose receptacle development by integrating epigenetic regulation and phytohormones signaling at low temperature.