Huang Zhichong, Han Xiao, He Kunrong, Ye Jingwen, Yu Chunlan, Xu Tingting, Zhang Juping, Du Jiancan, Fu Qiantang, Hu Yanru
School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230027, China.
CAS Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming, Yunnan 650223, China.
Plant Cell. 2025 Mar 5;37(3). doi: 10.1093/plcell/koaf046.
Abscisic acid (ABA) suppresses Arabidopsis (Arabidopsis thaliana) seed germination and post-germinative growth. Nitrate stimulates seed germination, but whether it directly regulates ABA signaling and the associated underlying molecular mechanisms remain unknown. Here, we showed that nitrate alleviates the repressive effects of ABA on seed germination independently of the nitric oxide (NO) pathway. Moreover, nitrate attenuates ABA signaling activated by ABSCISIC ACID INSENSITIVE3 (ABI3) and ABI5, two critical transcriptional regulators of the ABA pathway. Mechanistic analyses demonstrated that ABI3 and ABI5 physically interact with the nitrate signaling-related core transcription factor NIN-LIKE PROTEIN 8 (NLP8). After ABA treatment, NLP8 suppresses ABA responses during seed germination without affecting ABA content. Notably, nitrate represses ABA signaling mainly through NLP8. Genetic analyses showed that NLP8 acts upstream of ABI3 and ABI5. Specifically, NLP8 inhibits the transcriptional functions of ABI3 and ABI5, as well as their ABA-induced accumulation. Additionally, NLP8 overexpression largely suppresses the ABA hypersensitivity of mutant plants exhibiting impaired NO biosynthesis or signaling. Collectively, our study reveals that nitrate counteracts the inhibitory effects of ABA signaling on seed germination and provides mechanistic insights into the NLP8-ABI3/ABI5 interactions and their antagonistic relationships in ABA signaling.
脱落酸（ABA）抑制拟南芥种子萌发和萌发后的生长。硝酸盐能刺激种子萌发，但它是否直接调节ABA信号传导以及相关的潜在分子机制仍不清楚。在此，我们表明硝酸盐可独立于一氧化氮（NO）途径减轻ABA对种子萌发的抑制作用。此外，硝酸盐减弱了由ABA途径的两个关键转录调节因子ABSCISIC ACID INSENSITIVE3（ABI3）和ABI5激活的ABA信号传导。机制分析表明，ABI3和ABI5与硝酸盐信号传导相关的核心转录因子NIN-LIKE PROTEIN 8（NLP8）发生物理相互作用。经过ABA处理后，NLP8在种子萌发期间抑制ABA反应，而不影响ABA含量。值得注意的是，硝酸盐主要通过NLP8抑制ABA信号传导。遗传分析表明，NLP8在ABI3和ABI5的上游起作用。具体而言，NLP8抑制ABI3和ABI5的转录功能以及它们由ABA诱导的积累。此外，NLP8过表达在很大程度上抑制了表现出NO生物合成或信号传导受损的突变植物的ABA超敏反应。总之，我们的研究揭示了硝酸盐可抵消ABA信号传导对种子萌发的抑制作用，并为NLP8-ABI3/ABI5相互作用及其在ABA信号传导中的拮抗关系提供了机制见解。
