Li Linxuan, Zhu Tingting, Song Yun, Feng Li, Farag Essam Ali Hassan, Ren Maozhi
Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences/Chengdu National Agricultural Science and Technology Center, Chengdu, China.
Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou, China.
Front Plant Sci. 2021 Jan 18;11:598654. doi: 10.3389/fpls.2020.598654. eCollection 2020.
ABSCISIC ACID INSENSITIVE5 (ABI5) is an important regulator of abscisic acid (ABA) signaling pathway involved in regulating seed germination and postgerminative growth in , which integrates various phytohormone pathways to balance plant growth and stress responses. However, the transcriptional regulatory mechanisms underlying ABI5 and its interacting proteins remain largely unknown. Here, we found that inhibition of AtTOR could increase ABA content by up-regulating the expression levels of ABA biosynthesis-related genes, and thus activated the expression of ABA-responsive genes. Pharmacological assay showed that mutant was insensitive to TOR inhibitor AZD8055, whereas overexpression lines were hypersensitive to AZD8055 in . Biochemical interaction assays demonstrated that ABI5 physically interacted with the RIBOSOMAL S6 KINASE2 (S6K2) protein in plant cell. S6K2 positively regulated ABA responses during seedling growth and upregulated ABA-responsive genes expression. Furthermore, genetic and physiological analysis indicated that overexpression lines enhanced resistance to drought treatment while interference lines were sensitive to drought. These results indicated that AtABI5 interacted with AtS6K2 to positively modulate ABA responses during seedling growth and shed light on a underlying mechanism of the crosstalk between TOR and ABA signaling pathways in modulating seedling growth in .
脱落酸不敏感5（ABI5）是脱落酸（ABA）信号通路中的一个重要调节因子，参与调节种子萌发和萌发后的生长，它整合了各种植物激素途径以平衡植物生长和应激反应。然而，ABI5及其相互作用蛋白的转录调控机制仍 largely未知。在这里，我们发现抑制AtTOR可以通过上调ABA生物合成相关基因的表达水平来增加ABA含量，从而激活ABA响应基因的表达。药理学分析表明，突变体对TOR抑制剂AZD8055不敏感，而超表达系在中对AZD8055敏感。生化相互作用分析表明，ABI5在植物细胞中与核糖体S6激酶2（S6K2）蛋白发生物理相互作用。S6K2在幼苗生长过程中正向调节ABA反应并上调ABA响应基因的表达。此外，遗传和生理学分析表明，超表达系增强了对干旱处理的抗性，而干扰系对干旱敏感。这些结果表明，AtABI5与AtS6K2相互作用以正向调节幼苗生长过程中的ABA反应，并揭示了TOR和ABA信号通路在调节幼苗生长中的潜在串扰机制。
