Gibberellin mediates spermidine-induced salt tolerance and the expression of GT-3b in cucumber

Shirong Guo,Yu Wang,Xinyu Si,Lei Kong,Weikang Liu,Xiaowen Gong,Jin Sun

doi:10.1016/j.plaphy.2020.04.041

Shirong Guo, Yu Wang + Show 5 more

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https://doi.org/10.1016/j.plaphy.2020.04.041

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Abstract

Numerous studies have demonstrated that spermidine (Spd) plays a critical role in salt tolerance in plants, but the associated mechanism remains largely unknown. In this study, we investigated the role of gibberellin (GA) in Spd-induced salt tolerance and the expression of GT-3b transcription factor in cucumber. The results showed that exogenous Spd significantly increased the salt tolerance of cucumber plants, while its effects were compromised in the presence of methylglyoxal bis-guanylhydrazone (MGBG), an inhibitor of Spd biosynthesis. Interestingly, the expression of GT-3b was significantly induced by Spd under salt stress, and the promoter sequence of GT-3b was predicted to contain cis-acting regulatory elements that could respond to phytohormones, such as GA, salicylic acid (SA), and methyl jasmonate (MeJA). The application of GA3, SA and MeJA as foliar spray could induce the expression of GT-3b. In addition, exogenous Spd dramatically increased the expression of genes related to GA biosynthesis, the activity of gibberellin oxidase, and the accumulation of GA3, whereas these effects were attenuated in the MGBG-treated plants. Furthermore, the application of GA3 increased GT-3b expression and salt tolerance, whereas these effects were blocked when the plants were treated with paclobutrazol (PAZ), a GA biosynthesis inhibitor. Similarly, the Spd-induced salt tolerance was compromised in the PAZ-treated plants. Our results suggest that GA mediates Spd-induced salt tolerance and the expression of GT-3b in cucumber. These results provide a new perspective for understanding the molecular mechanism of Spd-regulated salt tolerance in plants.

Highlights

IntroductionGT-3b binds to the GT-1 element in the promoter of S adenosylmethionine synthase ( S-adenosylmethionine synthase (SAMs) ) gene, the key gene of spermidine (Spd) biosynthesis, to regulate its expression, thereby increasing the salt tolerance of cucumber plants
Background Transcription factorGT-3b binds to the GT-1 element in the promoter of S adenosylmethionine synthase ( S-adenosylmethionine synthase (SAMs) ) gene, the key gene of spermidine (Spd) biosynthesis, to regulate its expression, thereby increasing the salt tolerance of cucumber plants
The results indicated that Spd could alleviate the inhibition of cucumber seedling growth by salt stress and reduce the degree of damage in plants

Summary

Introduction

GT-3b binds to the GT-1 element in the promoter of S adenosylmethionine synthase ( SAMs ) gene, the key gene of spermidine (Spd) biosynthesis, to regulate its expression, thereby increasing the salt tolerance of cucumber plants. Transcription factors are key components that generate specific stress responses They manipulate the transcriptional expression of a variety of stress-tolerant genes and control a wide range of downstream metabolism pathways. Northern blotting indicates that the expression level of the GT–1 protein RML1 is significantly upregulated in rice seedling leaves infected with rice blast [8] It wasfound that GT–4 interacts with TEM2 to regulate the salt response gene Cor15A to improve salt tolerance [9]. Our previous work found that the GT–3b is induced by salt stress and binds to the GT–1 element in the promoter of S-adenosylmethionine synthase gene (CsSAMs) to trigger its expression in cucumber [11], thereby improving the salt tolerance of cucumber plants

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