Abstract
Key messageHbMBF1a was isolated and characterized in H. brevisubulatum, and overexpressed HbMBF1a could enhance the salt tolerance and ABA insensitivity in Arabidopsis thaliana. The transcript levels of stress-responsive genes were significantly increased in the transgenic lines under salt and ABA conditions.Salinity is an abiotic stress that considerably affects plant growth, yield, and distribution. Hordeum brevisubulatum is a halophyte that evolved to become highly tolerant to salinity. Multiprotein bridging factor 1 (MBF1) is a transcriptional coactivator and an important regulator of stress tolerance. In this study, we isolated and characterized HbMBF1a based on the transcriptome data of H. brevisubulatum grown under saline conditions. We overexpressed HbMBF1a in Arabidopsis thaliana and compared the phenotypes of the transgenic lines and the wild-type in response to stresses. The results indicated that HbMBF1a expression was induced by salt and ABA treatments during the middle and late stages. The overexpression of HbMBF1a in A. thaliana resulted in enhanced salt tolerance and ABA insensitivity. More specifically, the enhanced salt tolerance manifested as the increased seed germination and seedling growth and development. Similarly, under ABA treatments, the cotyledon greening rate and seedling root length were higher in the HbMBF1a-overexpressing lines, suggesting the transgenic plants were better adapted to high exogenous ABA levels. Furthermore, the transcript levels of stress-responsive genes were significantly increased in the transgenic lines under salt and ABA conditions. Thus, HbMBF1a is a positive regulator of salt and ABA responses, and the corresponding gene may be useful for producing transgenic plants that are salt tolerant and/or ABA insensitive, with few adverse effects. This study involved a comprehensive analysis of HbMBF1a. The results may provide the basis and insight for the application of MBF1 family genes for developing stress-tolerant crops.
Highlights
Salt stress is a serious threat affecting crop production and distribution
The HbMBF1a expression pattern in response to salt stress was consistent with the transcriptome data (Fig. 2e). These results suggested that HbMBF1a expression is regulated by salt and exogenous abscisic acid (ABA), but not during the early stage of the stress treatments
The results suggested that HbMBF1a overexpression may enhance the adaptability of A. thaliana to exogenous ABA
Summary
Salt stress is a serious threat affecting crop production and distribution. High salinity, especially during the seedling stage, dramatically decreases crop yield and quality, and may result in the death of all seedlings. The main objective of this study was to functionally characterize saltresponsive genes in the halophyte Hordeum brevisubulatum and use them for breeding halotolerant crops. Previous studies have identified and described the salt-tolerance genes cloned from model plant species such as Arabidopsis thaliana (Kim et al 2007; Alavilli et al 2017). The salient feature of H. brevisubulatum is its high tolerance to multiple abiotic stresses, including salinity, alkalinity and drought, enabling it to grow in the salinealkali grasslands of northern China, where it is used as a major forage crop for livestock (Li et al 2012). Previous studies have investigated H. brevisubulatum regarding ion balance and gene functions (Zhang et al 2015), very little is known about the molecular mechanism underlying the resistance of H. brevisubulatum to stress
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