Table_1_The Auxin Signaling Repressor IAA8 Promotes Seed Germination Through Down-Regulation of ABI3 Transcription in Arabidopsis.docx

Seed germination is a complex biological process controlled by various regulators, including phytohormones. Among these, abscisic acid and gibberellic acid inhibit and promote seed germination, respectively. Many studies have addressed the biological roles of auxin in plant growth and development, but very few have considered its role in seed germination. Here, we identified a novel function of the auxin signaling repressor Aux/IAA8 during seed germination. The IAA8 loss-of-function mutant iaa8-1 exhibited delayed seed germination. The phenotype of iaa8-1 was restored by ectopic expression of IAA8. Interestingly, IAA8 accumulated to high levels during seed germination, which was achieved not only by increased protein synthesis but also by the stabilization of IAA8 protein. We also showed that IAA8 down-regulates the transcription of ABSCISIC ACID INSENSITIVE3 (ABI3), a negative regulator of seed germination. Our study, thus strongly suggest that the auxin signaling repressor IAA8 acts as a positive regulator of seed germination in Arabidopsis thaliana.

种子萌发是一类受多种调控因子（包括植物激素）调控的复杂生物学过程。其中，脱落酸（abscisic acid）与赤霉素（gibberellic acid）分别抑制和促进种子萌发。既往诸多研究已阐明生长素（auxin）在植物生长发育中的生物学功能，但针对其在种子萌发过程中作用的报道却相对匮乏。本研究鉴定得到生长素信号抑制因子Aux/IAA8在种子萌发过程中的全新功能。IAA8功能缺失突变体iaa8-1表现出种子萌发延迟的表型，通过异位表达IAA8即可恢复该突变体的表型。值得注意的是，IAA8在种子萌发过程中会积累至较高水平，这一过程不仅依赖于蛋白质合成水平的提升，同时也得益于IAA8蛋白稳定性的增强。本研究同时证实，IAA8可下调种子萌发负调控因子脱落酸不敏感3（ABSCISIC ACID INSENSITIVE3, ABI3）的转录水平。综上，本研究有力证明生长素信号抑制因子IAA8可作为拟南芥（Arabidopsis thaliana）种子萌发的正调控因子发挥作用。