自噬蛋白ATG8是真核生物自噬过程中的核心组分，它们能直接与自噬货物受体等蛋白在细胞质中相互作用，从而使后者通过溶酶体或液泡降解。然而，我们最近研究发现拟南芥ATG8I蛋白能特异与ABI5转录因子在细胞核内相互作用形成复合物。ATG8I主要在干种子中表达，并受ABA激素诱导；表型分析发现atg8i突变体对ABA敏感，且该表型依赖于ABI5。上述结果暗示ATG8I可能具有不依赖于自噬过程的转录调控功能。为了深入研究ABI5-ATG8I复合物调控ABA信号转导的分子机制，本项目将采用分子生物学、遗传学及生物化学的方法手段，系统分析ATG8I调控ABA反应的生物学功能，揭示它与ABI5之间的遗传关系，并详细阐明它对ABI5蛋白稳定性、转录活性或DNA结合能力等的调控作用。本项目的研究结果不仅有助于人们深入理解ABI5介导的信号网络，还有可能揭示自噬蛋白在基因转录调控方面的生物学功能及其分子机理。

Autophagy is a highly conserved degradation and recycling process in eukaryotes. Acting as critical components in autophagic processes, ATG8 (AUTOPAHGY 8) family proteins have been shown to physically interact with cargo receptors in cytoplasm and mediate their degradation through the lysosome or vacuole. However, we recently found that Arabidopsis ATG8I protein specifically interacts with ABI5 transcription factor in the nucleus, suggesting that it may function as a modulator of transcription. ATG8I is predominantly expressed in dry seeds and strongly induced by abscisic acid (ABA) treatment. Phenotypic analysis showed that atg8i mutants are more sensitive to ABA than the wild type during seed germination. Further genetic analysis demonstrated that the ABA-hypersensitive phenotype of atg8i-1 plants is dependent on ABI5. These results suggest that ATG8I may be directly involved in ABA signaling through physically interacting with ABI5 transcription factor. To test this possibility, we will undertake molecular and genetic approaches in this project to further clarify the roles of ATG8I and the genetic interaction between ATG8I and ABI5 during seed germination. Moreover, we will investigate whether ATG8I interferes with the degradation, transcriptional function and/or DNA-binding activity of ABI5. Our study may not only contribute to explore the molecular mechanisms of ABI5-mediated ABA signaling, but also help understand the transcription functions of autophagy-related proteins.