High temperature during grain filling induces transgenerational heat stress memory in rice (Oryza sativa L.)

在相同的非胁迫条件下，高温条件下发育的种子萌发明显延迟。这种发芽延迟是由于ABA分解代谢基因和α-淀粉酶基因的超甲基化引起的吸胀后转录变化。Chop-qPCR和MeDIP-qPCR均证实了靶基因的高甲基化水平，结果表明ABA分解代谢基因和α-淀粉酶基因的高甲基化与热胁迫种子延迟萌发有关。在自然条件下，与对照植株相比，在总生物量不变的情况下，由热胁迫种子生长的植株在营养生长过程中分蘖增多，植株高度降低。收获时，热胁迫植株单株总穗数增加，总穗数增加，产量增加。其他产量指标如每穗粒数、千粒重、收获指数和结实率保持不变。通过对其他22个粳稻品种的观察，我们发现早花表型和叶片形态变化并不是品种特有的性状。不同品种籽粒灌浆过程中的热胁迫对后代的跨代记忆有不同程度的影响。

Seeds developed under high temperature showed significantly delayed germination compared to control under the same non-stressed condition. This delay in germination was due to transcriptional changes after imbibition caused by hyper-methylation of ABA catabolism genes, and α-amylase gene. Higher methylation levels of target genes were confirmed by both Chop-qPCR and MeDIP-qPCR, which showed similar results stating that hyper-methylation of ABA catabolism genes and of α-amylase genes was involved in delayed seed germination of heat stressed seeds.At natural condition, plants grown from heat stressed seeds developed more tillers together with reduced height during vegetative growth despite unchanged total biomass compared to control plants. At harvest, heat stressed plants showed higher total panicle per plant, resulting in higher total spikelet number resulting higher yield. Other yield components, spikelet per panicle, 1000-grain weight, harvest index and seed setting rate, remained unchanged.We observed that early flowering phenotype and changes in leaf morphology were not cultivar-specific traits, by observing other 22 Japonica rice cultivars. Cultivar differences show that heat stress during grain filling induces transgenerational memory to the progeny to some content depending on cultivars.