The crosstalk between Target of Rapamycin (TOR) and Jasmonic Acid (JA) signaling existing in Arabidopsis and cotton

Yun Song,Raju Datla,Fangjie Xiong,Fengping Zhuo,Fuguang Li,Xueyan Zhang,Ge Zhao,Maozhi Ren,Zuoren Yang,Linxuan Li,Chaojun Zhang

doi:10.1038/srep45830

Abstract

Target of rapamycin (TOR) acts as an important regulator of cell growth, development and stress responses in most examined diploid eukaryotes. However, little is known about TOR in tetraploid species such as cotton. Here, we show that TORC1-S6K-RPS6, the major signaling components, are conserved and further expanded in cotton genome. Though the cotton seedlings are insensitive to rapamycin, AZD8055, the second-generation inhibitor of TOR, can significantly suppress the growth in cotton. Global transcriptome analysis revealed that genes associated with jasmonic acid (JA) biosynthesis and transduction were significantly altered in AZD8055 treated cotton seedlings, suggesting the potential crosstalk between TOR and JA signaling. Pharmacological and genetic approaches have been employed to get further insights into the molecular mechanism of the crosstalk between TOR and JA. Combination of AZD8055 with methyl jasmonate can synergistically inhibit cotton growth, and additionally JA levels were significantly increased when cotton seedlings were subjected to AZD8055. JA biosynthetic and signaling mutants including jar1, coi1-2 and myc2-2 displayed TOR inhibitor-resistant phenotypes, whereas COI1 overexpression transgenic lines and jaz10 exhibited sensitivity to AZD8055. Consistently, cotton JAZ can partially rescue TOR-suppressed phenotypes in Arabidopsis. These evidences revealed that the crosstalk between TOR and JA pathway operates in cotton and Arabidopsis.

Highlights

Compared to great progress made in the understanding of Target of rapamycin (TOR) signaling in animals and yeasts, relatively less is known about this ancient and important regulatory system in higher plants
We found the putative homologous gene sequences encoding the key proteins of TORC1 complex including TOR, RAPTOR, and LST8; no putative homologs of TORC2specific proteins, such as RICTOR and SIN1, were present in cotton genome (Table 1 and Supplementary Table 1)
It should be noted that besides the two TOR homologs, four putative RAPTOR homologs were found, but only one copy of LST8 and FKBP12 can be detected in cotton genome (Supplementary Table 1). These observations indicate that TOR and RAPTOR have been duplicated during the evolution of cotton genome from diploid to heterotetraploid whereas one copy of LST8 and FKBP12 was lost during this process, indicating that TOR and RAPTOR may play more crucial parts in the evolutionary history and life strategies of cotton (Supplementary Table 1)

Summary

Introduction

Compared to great progress made in the understanding of TOR signaling in animals and yeasts, relatively less is known about this ancient and important regulatory system in higher plants. Inhibitors, which were named after active-site TOR inhibitors (asTORis) including AZD8055 (AZD), Torin[1] and Torin[2], can effectively inhibit TOR activity and retard plant growth[8,9,10]. A recent transcriptome analysis of Arabidopsis seedlings exposed to AZD showed that TOR regulated photosynthesis and phytohormone signaling pathways including jasmonic acid (JA) signaling pathway[11]. These results implied the potential crosstalk between TOR and JA, direct experimental evidence supporting this interaction remains largely elusive. To deal with environmental stresses, crop plants like cotton frequently encounter yield penalties resulting from effects on growth and development. Our results provide new evidences showing a connection between TOR and JA signaling pathways and demonstrate that TOR has a negatively effect on JA signaling pathway

Methods

Results

Conclusion