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，高温下发育的种子萌发明显滞后于对照。这种萌发延迟是由于脱落酸分解代谢基因和α-淀粉酶基因的高甲基化引起的吸胀后转录的变化。CHOP-qPCR法和MeDIPqPCR法都证实了目标基因的甲基化水平较高，这表明脱落酸分解代谢基因和α-淀粉酶基因的高甲基化与种子萌发延迟有关。在自然条件下，尽管总生物量与对照相比没有变化，但热胁迫种子生长的植株在营养生长过程中发育了更多的分蘖和降低的高度。在收获时，高温胁迫植株表现出更高的单株总穗数，从而导致更多的总小穗数，从而获得更高的产量。其他产量构成因素，如每穗实粒数、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，我们观察到早花表型和叶片形态变化不是品种特有的性状。品种差异表明，灌浆过程中的高温胁迫会诱导后代产生一定程度的跨代记忆，具体程度取决于品种。

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.