逆境胁迫下山新杨PdbHMGs基因表达模式分析

Expression Pattern Analysis of PdbHMGs Genes in Populus davidiana×P.bolleana under Abiotic Stress

为了初步探究山新杨HMG(High mobility group proteins)基因在非生物胁迫下的功能,本研究从山新杨(Populus davidiana×P.bolleana)中克隆获得HMGs基因,研究HMGs抗逆功能。利用同源序列比对,在山新杨中找到7条拟南芥(Arabidopsis thaliana)HMGs的同源基因(命名为PdbHMG1~7)。利用生物信息学工具对PdbH⁃MG1~7进行序列分析。此外,通过qRT-PCR探究不同逆境胁迫下PdbHMG1~7基因在山新杨根和叶中的表达模式。PdbHMG1-7 ORF长度为456~2004 bp,编码氨基酸残基数为151~667,编码蛋白相对分子质量为16.72~75.54 kDa,理论等电点为5.35~9.36,且7个PdbHMG蛋白均为亲水性蛋白。多序列比对与进化树分析结果表明,7个PdbHMGs基因均含有保守的HMG-box结构域,都属于HMGB亚家族。顺式作用元件的分析结果表明,PdbHMGs基因的启动子序列包含多种响应激素和逆境胁迫元件。高盐、干旱、重金属和激素等胁迫处理后表达模式分析结果显示,7个PdbHMGs基因在山新杨根和叶中的表达至少在一个胁迫处理时间点发生了显著变化。在叶片中,PdbHMG2在NaCl、ABA、PEG_(6000)和CdCl_(2)胁迫下被诱导几乎全部为显著上调表达,而PdbHMG7则全部为下调表达;在NaCl和CdCl_(2)胁迫下,PdbHMG1、PdbHMG3和PdbHMG6在整个胁迫过程中几乎全部为显著上调表达。在根中,NaCl处理整个过程中PdbHMG3和PdbHMG5的表达趋势全部显著上调,而PdbHMG6在NaCl胁迫过程中除9~12 h无明显表达外,其余胁迫时间点全部为显著下调表达;在ABA处理过程中,PdbHMG6在根中全部为下调表达。7个PdbHMGs基因至少能在1种器官中对1种胁迫处理做出应答,但响应的胁迫类型和机制可能不同。本研究为后续进一步研究山新杨PdbHMGs家族基因的功能提供了参考。

In order to investigate the function of HMG(High mobility group proteins)genes under abiotic stresses in Populus davidiana×P.bolleana,the HMG genes were cloned and the stress tolerant function of HMGs was identified,and the theoretical foundation for using the gene in tree breeding through genetic engineering was laid.Seven homologous genes of Arabidopsis HMGs(named PdbHMG1-7)were found by homologous sequence alignment,and sequence analysis of PdbHMG1-7 was performed using bioinformatics tools respectively,the expression patterns of PdbHMG1-7 gene in leaves and roots of Populus davidiana×P.bolleana under different stresses were investigated by qRT-PCR.Results The ORF length of PdbHMG1-7 were 456-2004 weight of the encoded protein were 16.72-75.54 kDa,and the theoretical isoelectric point were 5.35-9.36,and the seven PdbHMG were hydrophilic proteins.The results of multiple sequence alignment and phylogenetic tree analysis showed that all 7 PdbHMG genes contained HMG-box conserved domains and belonged to HMGB subfamily.The analysis results of cis-acting elements contained in the promoter showed that the promoter sequence of PdbHMG genes contained a variety of elements in response to hormones and stress.The expression pattern analysis showed that the expression levels of seven PdbHMGs in roots and leaves under NaCl,PEG_(6000),ABA and CdCl_(2)stress treatment changed in at least one stress treatment time point respectively.In leaves,PdbHMG2 were induced under the stress of NaCl,PEG_(6000),ABA and CdCl_(2),and almost all of them were significantly up-regulated respectively,but PdbHMG7 was down-regulated.Under NaCl and CdCl_(2)stress,PdbHMG1,PdbHMG3 and PdbHMG6 were almost significantly up-regulated during the whole stress process respectively.The expressions of PdbHMG3 in leaves were also significantly up-regulated at most time points under NaCl and CdCl_(2)stress.In roots,the expression of PdbHMG3 and PdbHMG5 was significantly upregulated in the whole process of NaCl treatment.However,PdbHMG6 was not significantly expressed during NaCl stress except for 9-12 h,the expression of PdbHMG6 was significantly down-regulated at other stress time points.During ABA treatment,PdbHMG6 was down-regulated in roots.Conclusion The results showed that seven PdbHMG genes could respond to at least one stress treatment in one organ,but the types and mechanisms of involved stress response might be different.This study provided a reference for further studying the function of PdbHMGs family genes in Populus davidiana×P.bolleana.