沙地云杉MYB转录因子家族鉴定及其对盐胁迫的响应

Identification of the MYB transcription factor family involved in response to salt stress in Picea mongolica

摘要:

沙地云杉(Picea mongolica)具有耐寒、耐旱及耐盐的优良特性，是“三北”地区生态建设及城市绿化的重要树种。MYB转录因子可以响应非生物胁迫及次生代谢产物合成过程，为鉴定沙地云杉MYB转录因子家族并探究其在盐胁迫过程中的响应，本研究以挪威云杉基因组及沙地云杉转录组数据为参考，共鉴定出196个MYBs家族成员。根据系统进化树，MYB转录因子家族分为7个亚类，其中，R2R3-MYB亚类基因数量最多，占84.77%，R-R和R1R2R3亚类数量最少，均占0.51%。基序、结构域、基因结构及保守性分析表明，同一亚类MYB转录因子具有高度保守性且具有相似基序和基因结构。不同盐胁迫梯度实验表明，沙地云杉最高的耐受盐胁迫浓度为1 000 mmol/L。在1 000 mmol/L盐胁迫浓度下设置不同处理时间(0、3、6、12、24 h)并测定转录组数据，共筛选出34个MYBs差异表达基因，表明其可能在调控盐胁迫过程中发挥着重要作用。对差异基因编码的蛋白进行理化性质分析发现，蛋白序列长度在89–731 aa，分子量约为10.19–79.73 kDa，等电点为4.80–9.91，不稳定系数41.20–70.99。亚细胞定位显示，大部分蛋白位于细胞核，3个蛋白位于叶绿体中。选取其中12个MYB基因进行实时荧光定量PCR (quantitative real-time PCR,qRT-PCR)验证，其表达模式与RNA-seq数据一致。本研究为后续探索沙地云杉中MYB家族成员在响应盐胁迫过程的功能及作用机制提供了数据支持。

Abstract:

Picea mongolica, known for its remarkable tolerance to cold, drought, and salinity, is a key species for ecological restoration and urban greening in the “Three Norths” region of China. MYB transcription factors are involved in plant responses to abiotic stress and synthesis of secondary metabolites. However, studies are limited regarding the MYB transcription factors in P. mongolica and their roles in salt stress tolerance. In this study, 196 MYBs were identified based on the genome of Picea abies and the transcriptome of P. mongolica. Phylogenetic analysis classified the MYB transcription factors into seven subclasses. The R2R3-MYB subclass contained the maximum number of genes (84.77%), while the R-R and R1R2R3 subclasses each represented the smallest proportion, at about 0.51%. The MYB transcription factors within the same subclass were highly conserved, exhibiting similar motifs and gene structures. Experiments with varying salt stress gradients revealed that P. mongolica could tolerate the salt concentration up to 1 000 mmol/L. From the transcriptome data of P. mongolica exposed to salt stress (1 000 mmol/L) for 0, 3, 6, 12, and 24 h, a total of 34 differentially expressed MYBs were identified, which suggested that these MYBs played a key role in regulating the response to salt stress. The proteins encoded by these differentially expressed genes varied in length from 89 aa to 731 aa, with molecular weights ranging from 10.19 kDa to 79.73 kDa, isoelectric points between 4.80 and 9.91, and instability coefficients from 41.20 to 70.99. Subcellular localization analysis indicated that most proteins were localized in the nucleus, while three were found in the chloroplasts. Twelve MYBs were selected for quantitative real-time PCR (qRT-PCR), which showed that their expression patterns were consistent with the RNA-seq data. This study provides valuable data for further investigation into the functions and mechanisms of MYB family members in response to salt stress in P. mongolica.