茶树CsbZIP4转录因子正调控拟南芥对盐胁迫响应

Positive Regulation of CsbZIP4 Transcription Factor on Salt Stress Response in Transgenic Arabidopsis

bZIP转录因子是真核生物中一类多功能蛋白家族,参与种子成熟、光信号调节、胁迫响应等多种生物学过程,拟南芥中根据序列相似性和保守域主要分为10个亚家族(A-I和S)。本文以茶树的C亚家族转录因子CsbZIP4为研究对象,调查非生物胁迫下的表达模式,及转化拟南芥后CsbZIP4过表达对耐盐性的影响。结果显示,在4℃低温、外源ABA、盐和干旱胁迫处理后,CsbZIP4的表达在茶树叶片中呈上调模式,特别是在盐和干旱胁迫下其表达分别上调2.9倍和2.2倍;而在根中,低温、盐和干旱胁迫均能显著抑制CsbZIP4的表达,其中盐胁迫能将其表达抑制2倍;荧光显微镜下观察CsbZIP4-GFP融合蛋白,将CsbZIP4定位于细胞核中;CsbZIP4的过表达能够降低转基因株系种子萌发时对外源ABA、盐胁迫的敏感性,在300mmolL^(-1)NaCl盐胁迫下,转化拟南芥植株过表达CsbZIP4增强抗性,其叶片的SPAD值较高,同时过表达株系中盐胁迫响应基因AtSOS1的表达显著增强。根据CsbZIP4正调控拟南芥的盐胁迫响应,推断CsbZIP4与茶树抵御盐胁迫密切相关。

Basic region / leucine zipper （bZIP） transcription factors is a multi-functional protein family in eukaryotes, which isinvolved in various biological processes including seed maturation, light signaling regulation and stress response. According tosequence similarity and conserved motifs, the AtbZIPs are classified into 10 groups （A, B, C, D, E, F, G, H, I, and S）. In this study,CsbZIP4 of C-group bZIP transcription factors was using as an objective, the expression patterns of CsbZIP4 in response toabiotic stress in tea plants were investigated, and the salinity tolerance caused by CsbZIP4 overexpression in Arabidopsis wasanalyzed. The CsbZIP4 from tea plant leaves was up-regulated under 4°C, exogenous ABA, salinity and dehydration stresses,especially the induction of salinity and dehydration stresses led to up-regulation of 2.9-fold and 2.2-fold, respectively. In roots,CsbZIP4 was down-regulated in response to cold, salinity and dehydration stresses, especially down-regulated by 2-fold undersalinity stress. Under fluorescence microscope, it was indicated that CsbZIP4 was located in nucleus. Constitutive overexpressionof CsbZIP4 in transgenic Arabidopsis lowered the plants’ sensitivity to exogenous ABA and salinity at germination stage. Moreover,CsbZIP4 overexpression lines exhibited higher salinity tolerance under 300 mmol L–1 NaCl conditions and higher SPAD values. AtSOS1, which is a salinity responsive gene, was strongly induced in overexpression lines. In conclusion, CsbZIP4 positivelyregulates salt stress response in Arabidopsis, and might be closely related to the tolerance to salinity stress in tea plant.