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Article|27 Jun 2022|OPEN
Target of rapamycin (TOR) regulates the response to low nitrogen stress via autophagy and hormone pathways in Malus hupehensis
Danyang Li1 ,† , Yuduan Ding1 ,† , Li Cheng1 ,† , Xiaoli Zhang1 , Siyuan Cheng1 , Ying Ye1 , Yongchen Gao1 , Ying Qin1 , Zhu Liu1 , Cuiying Li1 , Fengwang Ma1 , and Xiaoqing Gong,1 ,
1State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, China
*Corresponding author. E-mail: fwm64@sina.com,gongxq0103@nwsuaf.edu.cn
Danyang Li,Yuduan Ding and Li Cheng contributed equally to the study.

Horticulture Research 9,
Article number: uhac143 (2022)
doi: https://doi.org/10.1093/hr/uhac143
Views: 85

Received: 17 Nov 2021
Accepted: 20 Jun 2022
Published online: 27 Jun 2022

Abstract

Target of rapamycin (TOR) is a highly conserved master regulator in eukaryotes; it regulates cell proliferation and growth by integrating different signals. However, little is known about the function of TOR in perennial woody plants. Different concentrations of AZD8055 (an inhibitor of TOR) were used in this study to investigate the role of TOR in the response to low nitrogen (N) stress in the wild apple species Malus hupehensis. Low N stress inhibited the growth of M. hupehensis plants, and 1 μM AZD alleviated this effect. Plants supplied with 1 μM AZD had higher photosynthetic capacity, which promoted the accumulation of biomass, as well as higher contents of N and anthocyanins and lower content of starch. Exogenous application of 1 μM AZD also promoted the development of the root system. Plants supplied with at least 5 μM AZD displayed early leaf senescence. RNA-seq analysis indicated that TOR altered the expression of genes related to the low N stress response, such as genes involved in photosystem, starch metabolism, autophagy, and hormone metabolism. Further analysis revealed altered autophagy in plants supplied with AZD under low N stress; the metabolism of plant hormones also changed following AZD supplementation. In sum, our findings revealed that appropriate inhibition of TOR activated autophagy and jasmonic acid signaling in M. hupehensis, which allowed plants to cope with low N stress. Severe TOR inhibition resulted in the excessive accumulation of salicylic acid, which probably led to programmed cell death in M. hupehensis.