背景回顾：Seed thermoinhibition, the repression of germination under high temperatures, prevents seedling establishment under potentially fatal conditions. Thermoinhibition is relevant for phenology and agriculture, particularly in a warming globe. 

提出问题：The temperature sensing mechanisms and signaling pathways sustaining thermoinhibition are unknown. 

主要发现：Here we show that thermoinhibition in Arabidopsis thaliana is not autonomously controlled by the embryo but is rather implemented by the endosperm. 

结果1-高温促进phyB失活，释放PIFs：High temperature is sensed through endospermic phyB by accelerating its reversion from the active signaling Pfr form into the inactive Pr form, as previously described in seedlings. This leads to thermoinhibition mediated by PIFs, mainly PIF1, PIF3 and PIF5.

结果2-胚乳PIFs抑制ABA代谢，促进胚乳ABA积累：Endospermic PIF3 represses the expression of the endospermic ABA catabolic gene CYP707A1 and promotes endospermic ABA accumulation and release towards the embryo to block its growth.  

结果3-胚乳ABA抑制胚胎PIF3：Furthermore, endospermic ABA represses embryonic PIF3accumulation that would otherwise promote embryonic growth. 

结论：Hence, under high temperatures PIF3 exerts opposite growth responses in the endosperm and embryo.

种子的热抑制作用，即在高温条件下种子萌发受到抑制，能够防止种子在不利环境条件下萌发影响幼苗生长。热抑制与物候和农艺息息相关，尤其是我们正面对全球气候变暖的挑战。然而，维持热抑制的温度感知机制和信号转导途径仍不清楚。本文中，作者发现拟南芥种子的热抑制并非由胚胎自主性控制的，而是通过胚乳来实现的。胚乳中的phyB会感知高温，然后加速其从激活态Pfr转变为非激活态Pr。这会导致由PIF1/3/5等PIFs介导的热抑制。胚乳中的PIF3能够抑制胚乳中ABA代谢基因CYP707A1的表达，从而促进胚乳中ABA的积累以及向胚胎的释放，进而阻断胚胎的生长。此外，胚乳中的ABA能够抑制胚胎中的PIF3积累，而PIF3又是胚胎生长的促进因子。因此，在高温条件下，PIF3在胚乳和胚胎中存在完全相反的生长响应。