Laboratory of Walnut Research Center, College of Forestry, Northwest A & F University, Yangling, 712100, Shaanxi, China.
BMC Genomics. 2020 Jul 10;21(1):474. doi: 10.1186/s12864-020-06879-2.
Walnut (Juglans regia) is an important tree cultivated worldwide and is exposed to a series of both abiotic and biotic stress during their life-cycles. The heat stress transcription factors (HSFs) play a crucial role in plant response to various stresses by regulating the expression of stress-responsive genes. HSF genes are classified into 3 classes: HSFA, HSFB, and HSFC. HSFA gene has transcriptional activation function and is the main regulator of high temperature-induced gene expression. HSFB gene negatively regulates plant resistance to drought and NaCl. And HSFC gene may be involved in plant response to various stresses. There are some reports about the HSF family in herbaceous plants, however, there are no reports about the HSFs in walnut.
In this study, based on the complete genome sequencing of walnut, the bioinformatics method was used and 29 HSF genes were identified. These HSFs covered 18 HSFA, 9 HSFB, and 2 HSFC genes. Phylogenetic analysis of these HSF proteins along with those from Arabidopsis thaliana showed that the HSFs in the two species are closely related to each other and have different evolutionary processes. The distribution of conserved motifs and the sequence analysis of HSF genes family indicated that the members of the walnut HSFs are highly conserved. Quantitative Real-Time PCR (qRT-PCR) analysis revealed that the most of walnut HSFs were expressed in the walnut varieties of 'Qingxiang' and 'Xiangling' under high temperature (HT), high salt and drought stress, and some JrHSFs expression pattern are different between the two varieties.
The complex HSF genes family from walnut was confirmed by genome-wide identification, evolutionary exploration, sequence characterization and expression analysis. This research provides useful information for future studies on the function of the HSF genes and molecular mechanism in plant stress response.
核桃（Juglans regia）是一种在全球范围内广泛种植的重要树种，在其生命周期中会受到一系列非生物和生物胁迫的影响。热激转录因子（HSFs）通过调节应激响应基因的表达，在植物对各种胁迫的反应中起着至关重要的作用。HSF 基因分为 3 类：HSFA、HSFB 和 HSFC。HSFA 基因具有转录激活功能，是高温诱导基因表达的主要调控因子。HSFB 基因负调控植物对干旱和 NaCl 的抗性。而 HSFC 基因可能参与植物对各种胁迫的反应。已有一些关于草本植物 HSF 家族的报道，但关于核桃 HSF 的报道尚不多见。
本研究基于核桃全基因组测序，采用生物信息学方法鉴定了 29 个 HSF 基因。这些 HSF 基因涵盖了 18 个 HSFA、9 个 HSFB 和 2 个 HSFC 基因。这些 HSF 蛋白与拟南芥的系统进化分析表明，这两个物种的 HSF 密切相关，且具有不同的进化过程。保守基序的分布和 HSF 基因家族的序列分析表明，核桃 HSF 成员高度保守。定量实时 PCR（qRT-PCR）分析显示，在高温（HT）、高盐和干旱胁迫下，大多数核桃 HSF 在‘清香’和‘香玲’两个品种中均有表达，而一些 JrHSFs 在两个品种中的表达模式不同。
通过全基因组鉴定、进化探索、序列特征分析和表达分析，证实了核桃中复杂的 HSF 基因家族的存在。本研究为进一步研究 HSF 基因在植物应激反应中的功能和分子机制提供了有价值的信息。
