背景回顾：In Citrus, the response to environmental floral inductive signals is inhibited by the presence of developing fruits. The mechanism involves epigenetic activation of the CcMADS19 locus (FLC orthologue), encoding a floral repressor. 

主要研究：To understand how this epigenetic regulation is reverted to allow flowering in the following season, we have forced precocious sprouting of axillary buds in fruit-bearing shoots, and examined the competence to floral inductive signals of old and new leaves derived from them. 

结果：We have found that CcMADS19 is enriched in repressive H3K27me3 marks in young, but not old leaves, revealing that axillary buds retain a silenced version of the floral repressor that is mitotically transmitted to the newly emerging leaves, which are able to induce flowering. 

结论：Therefore, we propose that flowering in Citrus is necessarily preceded by vegetative sprouting, so that the competence to respond to floral inductive signals is reset in the new leaves.

 摘 要 

在柑橘属物种中，响应于环境花诱导信号在有正在发育果实的植株中是被抑制的。该过程涉及到了开花抑制因子FLC在柑橘中的同源基因CcMADS19的表观激活。为了理解该表观调控是如何发生逆转，以便在下一季来临时能够正常开花，作者强行让带有果实的枝上的腋芽提前开花，并研究了其新老叶片中的开花诱导信号。作者发现新叶片中CcMADS19基因富集了抑制性的H3K27me3标记，但是老叶片中并没有，说明腋芽保留了开花抑制因子的沉默状态，并可以通过有丝分裂传递给新形成的叶片，从而诱导开花。因此，作者提出柑橘开花必需发生在营养芽发芽之后，以便于在新叶中重置对花诱导信号的响应能力。