The mechanism underlying the ability of rice to germinate underwater is a largely enigmatic but key research question highly relevant to rice cultivation. Moreover, although rice is known to accumulate salicylic acid (SA), SA biosynthesis is poorly defined, and its role in underwater germination is unknown. It is also unclear whether peroxisomes, organelles essential to oilseed germination and rice SA accumulation, play a role in rice germination. Here, we show that submerged imbibition of rice seeds induces SA accumulation to promote germination in submergence. Two submergence-induced peroxisomal Oryza sativa cinnamate:CoA ligases (OsCNLs) are required for this SA accumulation. SA exerts this germination-promoting function by inducing indole-acetic acid (IAA) catabolism through the IAA-amino acid conjugating enzyme GH3. The metabolic cascade we identified may potentially be adopted in agriculture to improve the underwater germination of submergence-intolerant rice varieties. SA pretreatment is also a promising strategy to improve submerged rice germination in the field.

水稻水下发芽能力的机制是一个很大程度上神秘但与水稻种植高度相关的关键研究问题。此外，尽管已知水稻会积累水杨酸（SA），但SA的生物合成尚不清楚，并且其在水下发芽中的作用尚不清楚。目前还不清楚过氧化物酶体（对油籽发芽和水稻 SA 积累至关重要的细胞器）是否在水稻发芽中发挥作用。在这里，我们发现水稻种子的水下吸胀会诱导 SA 积累，从而促进水下发芽。SA 的积累需要两种浸没诱导的过氧化物酶体稻肉桂酸辅酶A 连接酶 (OsCNL)。 SA 通过 IAA-氨基酸结合酶 GH3 诱导吲哚乙酸 (IAA) 分解代谢，从而发挥这种促进发芽的功能。我们确定的代谢级联可能会在农业中采用，以改善不耐淹水稻品种的水下发芽。 SA 预处理也是一种有前途的改善田间沉水水稻发芽的策略。