Background

Tibetan hulless barley (Hordeum vulgare var. nudum), adjusting to the harsh environment on Qinghai–Tibet Plateau, is a good subject for analyzing drought tolerance mechanism. Several unannotated differentially expressed genes (DEGs) were identified through our previous RNA-Seq study using two hulless barley accessions with contrasting drought tolerance. One of these DEGs, HVU010048.2, showed up-regulated pattern under dehydration stress in both drought tolerant (DT) and drought susceptible (DS) accessions, while its function in drought resistance remains unknown. This new gene was named as HvLRX (light responsive X), because its expression was induced under high light intensity while suppressed under dark.

Objective

To provide preliminary bioinformatics prediction, expression pattern, and drought resistance function of this new gene.

Methods

Bioinformatics analysis of HvLRX were conducted by MEGA, PlantCARE, ProtParam, CELLO et al. The expression pattern of HvLRX under different light intensity, dehydration shock, gradual drought stress, NaCl stress, polyethylene glycol (PEG) 6000 stress and abscisic acid (ABA) treatment was investigated by quantitative reverse transcription-polymerase chain reaction (RT-qPCR). The function of HvLRX was analyzed by virus induced gene silencing (VIGS) in hulless barley and by transgenic method in tobacco.

Results

Full cDNAs of HvLRX were cloned and compared in three hulless barley accessions. Homologues of HvLRX protein in other plants were excavated and their phylogenetic relationship was analyzed. Several light responsive elements (ATC-motif, Box 4, G-box, Sp1, and chs-CMA1a) were identified in its promoter region. Its expression can be promoted under high light intensity, dehydration shock, gradual drought stress, PEG 6000, and NaCl stress, but was almost unchanged in ABA treatment. HvLRX-silenced plants had a higher leaf water loss rate (WLR) and a lower survival rate (SR) compared with controls under dehydration stress. The infected leaves of HvLRX-silenced plants lost their water content quickly and became withered at 10 dpi. The SR of HvLRX overexpressed transgenic tobacco plants was significantly higher than that of wild-type plants. These results indicated HvLRX play a role in drought resistance. Besides, retarded vegetative growth was detected in HvLRX-silenced hulless barley plants, which suggested that this gene is important for plant development.

Conclusions

This study provided data of bioinformatics, expression pattern, and function of HvLRX. To our knowledge, this is the first report of this new dehydration and light responsive gene.

中文翻译：

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青稞（Hordeum vulgare var. nudum）中新的脱水光响应基因HvLRX的鉴定

背景

青藏大麦（Hordeum vulgare var. nudum）适应青藏高原的恶劣环境，是分析耐旱机制的良好课题。通过我们之前的 RNA-Seq 研究，我们使用两种具有不同耐旱性的无壳大麦种质鉴定了几个未注释的差异表达基因 (DEG)。其中一个DEGs，HVU010048.2，在耐旱（DT）和易旱（DS）种质中均在脱水胁迫下显示出上调模式，而其在抗旱中的功能仍然未知。这个新基因被命名为HvLRX（光响应X），因为它的表达在高光强度下被诱导，而在黑暗中被抑制。

客观的

提供该新基因的初步生物信息学预测、表达模式和抗旱功能。

方法

HvLRX的生物信息学分析由 MEGA、PlantCARE、ProtParam、CELLO 等人进行。通过定量逆转录-聚合酶链反应（RT-qPCR）研究了HvLRX在不同光照强度、脱水休克、逐渐干旱胁迫、NaCl胁迫、聚乙二醇（PEG）6000胁迫和脱落酸（ABA）处理下的表达模式。HvLRX的功能在去壳大麦中通过病毒诱导基因沉默 (VIGS) 和在烟草中通过转基因方法进行了分析。

结果

克隆了HvLRX的完整 cDNA，并在三个无壳大麦种质中进行了比较。挖掘了其他植物中HvLRX蛋白的同源物，并分析了它们的系统发育关系。在其启动子区域鉴定了几种光响应元件（ATC 基序、Box 4、G-box、Sp1 和 chs-CMA1a）。在高光、脱水休克、渐进干旱胁迫、PEG 6000和NaCl胁迫下，其表达均得到促进，而ABA处理几乎没有变化。与脱水胁迫下的对照相比， HvLRX沉默的植物具有较高的叶片失水率 (WLR) 和较低的存活率 (SR)。HvLRX沉默植物的受感染叶片迅速失去水分并在 10 dpi 时枯萎。HvLRX的 SR过表达的转基因烟草植物显着高于野生型植物。这些结果表明HvLRX在抗旱中发挥作用。此外，在HvLRX沉默的无壳大麦植物中检测到营养生长延迟，这表明该基因对植物发育很重要。

结论

本研究提供了HvLRX的生物信息学、表达模式和功能数据。据我们所知，这是对这种新的脱水和光反应基因的首次报道。