摘要：

为了解谷子中SibHLH19的功能,以抗病谷子材料十里香叶片cDNA和基因组DNA为模板,分别克隆到SibHLH19基因的CDS序列和启动子序列,并利用生物信息学在线工具分析了启动子顺式作用元件及生物学特征;采用Real-time PCR技术检测了SibHLH19转录因子在谷子不同组织部位和抗谷锈病过程中的表达丰度变化;利用SDS-PAGE技术分析了该基因原核表达特征。结果表明,SibHLH19转录因子CDS序列全长843 bp,编码280个氨基酸,预测蛋白质分子质量为29.97 ku,理论等电点pI为5.85,编码蛋白质化学式为C₁₂₉₆H₂₀₇₁N₃₉₇O₄₀₀S₁₁,含有一个bHLH保守结构域,属于不稳定亲水性蛋白质。该蛋白质二级结构的最大元件是无规则卷曲,最小元件为β-转角。进化分析表明,SibHLH19与禾本科植物糜子(RLM85279.1)、哈氏黍(PUZ71581.1)和柳枝稷(XP_039835205.1)氨基酸序列的同源性较高,与小麦(KAF7059972.1)、节节麦(XP_040244423.1)同源性最低。启动子顺式作用元件分析表明,该基因启动子区存在多个激素、胁迫等应答元件。组织表达分析表明,该基因主要在谷子苗期表达,并以苗期地上部分表达量最高,孕穗期几乎无表达。在谷子响应谷锈菌生物胁迫反应的24 h内,SibHLH19基因在抗病反应8,16 h上调表达,而感病反应中仅在16 h略微上调表达,其余时间均下调表达,推测SibHLH19在谷子抗锈病反应中起正调控作用。构建的原核表达载体pET30a-SibHLH19经0.1 mmol/L IPTG诱导能表达出表观分子质量约44 ku的SibHLH19融合蛋白。

关键词: 谷子, 谷子锈病, bHLH转录因子, 基因表达, 抗病反应

Abstract:

In order to understand the function of SibHLH19 in foxtail millet,the CDS sequence and promoter sequence of SibHLH19 gene were separately cloned with the leaf cDNA and genomic DNA from resistance material Shilixiang as template by PCR.Promoter cis-acting elements and biological characteristics were analyzed using bioinformatics online tools.Then the expression patterns of SibHLH19 in different tissues and during the process to rust resistance were surveyed by qRT-PCR,respectively.Lastly the prokaryotic expression characteristics for the gene were detected by SDS-PAGE,laying a theoretical foundation for further research on SibHLH19 gene function and disease resistance mechanism.The results showed that the CDS sequence of the SibHLH19 transcription factor was 843 bp in length,encoding a total of 280 amino acids,the predicted protein molecular weight was 29.97 ku.The theoretical isoelectric point was 5.85,and the encoded protein chemical formula was C₁₂₉₆H₂₀₇₁N₃₉₇O₄₀₀S₁₁,containing a bHLH conserved domain,belonging unstable hydrophilic protein.The largest element of the protein's secondary structure was random coils,and the smallest element was a β-turn.Evolutionary analysis showed that SibHLH19 had the higher homology to the amino acid sequences of Panicum miliaceum (RLM85279.1),Panicum hallii (PUZ71581.1)and Panicum virgatum (XP_039835205.1),and had the lowest homology with Triticum aestivum(KAF7059972.1)and Aegilops tauschii subsp.strangulata (XP_040244423.1).The analysis of the promoter cis-acting elements showed that there were multiple response elements such as hormones and stresses in the promoter region of the SibHLH19 gene.Tissue expression analysis showed that the gene was mainly expressed at the seedling stage with the highest expression in the aboveground part,and was almost no expression at the booting stage.Within 24 hours of the response to the biotic stress of rust disease in foxtail millet,the SibHLH19 gene expression was up-regulated at 8 and 16 h in the disease resistance response,while its expression was only slightly up-regulated at 16 h and down-regulated at the rest of the time points in the susceptible response.It was speculated that SibHLH19 played a positive regulatory role in the resistance response to rust disease in foxtail millet.The constructed prokaryotic expression vector pET30a-SibHLH19 could express the SibHLH19 fusion protein with an apparent molecular weight of about 44 ku after being induced by 0.1 mmol/L IPTG.

Key words: Foxtail millet, Foxtail millet rust, bHLH transcription factor, Gene expression, Disease resistance