BrrICE1.1 is associated with putrescine synthesis through regulation of the arginine decarboxylase gene in freezing tolerance of turnip (Brassica rapa var. rapa)

Xin Yin,Yan Li,Yunqiang Yang,Yanqiu Lv,Danni Yang,Yongping Yang,Yanling Yue

doi:10.1186/s12870-020-02697-6

Abstract

BackgroundIn the agricultural areas of Qinghai-Tibet Plateau, temperature varies widely from day to night during the growing season, which makes the extreme temperature become one of the limiting factors of crop yield. Turnip (Brassica rapa var. rapa) is a traditional crop of Tibet grown in the Tibet Plateau, but its molecular and metabolic mechanisms of freezing tolerance are unclear.ResultsHere, based on the changes in transcriptional and metabolic levels of Tibetan turnip under freezing treatment, the expression of the arginine decarboxylase gene BrrADC2.2 exhibited an accumulative pattern in accordance with putrescine content. Moreover, we demonstrated that BrrICE1.1 (Inducer of CBF Expression 1) could directly bind to the BrrADC2.2 promoter, activating BrrADC2.2 to promote the accumulation of putrescine, which was verified by RNAi and overexpression analyses for both BrrADC2.2 and BrrICE1.1 using transgenic hair root. The function of putrescine in turnip was further analyzed by exogenous application putrescine and its inhibitor DL-α-(Difluoromethyl) arginine (DFMA) under freezing tolerance. In addition, the BrrICE1.1 was found to be involved in the ICE1-CBF pathway to increase the freezing stress of turnip.ConclusionsBrrICE1.1 could bind the promoter of BrrADC2.2 or CBFs to participate in freezing tolerance of turnip by transcriptomics and targeted metabolomics analyses. This study revealed the regulatory network of the freezing tolerance process in turnip and increased our understanding of the plateau crops response to extreme environments in Tibet.

Highlights

In the agricultural areas of Qinghai-Tibet Plateau, temperature varies widely from day to night during the growing season, which makes the extreme temperature become one of the limiting factors of crop yield
Through analysis of differential gene expressions and weighted gene coexpression correlation network analysis (WGCN A) by transcriptome and metabonomic studies, we identified a key gene BrrADC2.2 that may be involved in putrescine metabolism
BrrADC2.2 (GenBank number: MN630676) was found to participate in polyamine synthesis, and the increase in BrrADC2.2 expression was consistent with the accumulation of putrescine under freezing treatment. These results suggested that BrrADC2.2 may play a key role in polyamine synthesis under freezing stress in turnip, and the upregulation of BrrADC2.2 expression and the increase in putrescine could be essential for freezing tolerance of turnip

Summary

Introduction

In the agricultural areas of Qinghai-Tibet Plateau, temperature varies widely from day to night during the growing season, which makes the extreme temperature become one of the limiting factors of crop yield. Rapa) is a traditional crop of Tibet grown in the Tibet Plateau, but its molecular and metabolic mechanisms of freezing tolerance are unclear. Polyamines are low molecular weight aliphatic polymers that are widely present in various organisms. Many types of polyamines, such as agmatine, putrescine, spermidine, spermine, and cadaverine, have been found in higher plants [1]. Putrescine acts as the first key factor in polyamine and the synthesis of polyamines begin with the synthesis of putrescine metabolism in most organisms. Putrescine in plants could be formed in two ways: arginine decarboxylase (ADC) and Orn decarboxylase (ODC) pathway [2, 3]. Spermidine synthetase (SPDS) catalyzes putrescine to produce spermidine, and spermine synthetase (SPMS) catalyzes the combination of spermidine and aminopropyl to produce spermine, in which the aminopropyl is generated from S-adenosylmethionine (SAM) by SAM decarboxylase [3]

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Conclusion