Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Sciences, Northeast Forestry University, Harbin, 150040, China.
Harbin Univ, Sch Geog & Tourism, Key Lab Heilongjiang Prov Cold Reg Wetlands Ecol &, Harbin, China.
Int J Biol Macromol. 2024 Nov;279(Pt 2):135193. doi: 10.1016/j.ijbiomac.2024.135193. Epub 2024 Aug 30.
The Myeloblastosis (MYB) transcription factor (TF) family is one of the largest transcription factor families in plants and plays an important role in various physiological processes. At present, there are few reports on birch (Betula platyphylla Suk.) of R2R3-MYB-TFs, and most BpMYBs still need to be characterized. In this study, 111 R2R3-MYB-TFs with conserved R2 and R3 MYB domains were identified. Phylogenetic tree analysis showed that the MYB family members of Arabidopsis thaliana and birch were divided into 23 and 21 subgroups, respectively. The latter exhibited an uneven distribution across 14 chromosomes. There were five tandem duplication events and 17 segmental duplication events between BpMYBs, and repeat events play an important role in the expansion of the family. In addition, the promoter region of MYBs was rich in various cis-acting elements, and MYB-TFs were involved in plant growth and development, light responses, biotic stress, and abiotic stress. RNA-sequencing (RNA-seq) and quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) results revealed that most R2R3-MYB-TFs in birch responded to salt stress. In particular, the expression of BpMYBs in the S20 subfamily was significantly induced by salt, drought, abscisic acid, and methyl jasmonate stresses. Based on the weighted co-expression network analysis of physiological and RNA-seq data of birch under salt stress, a key MYB-TF BpMYB95 (BPChr12G24087), was identified in response to salt stress, and its expression level was induced by salt stress. BpMYB95 is a nuclear localization protein with transcriptional activation activity in yeast and overexpression of this gene significantly enhanced salt tolerance in Saccharomyces cerevisiae. The qRT-PCR and histochemical staining results showed that BpMYB95 exhibited the highest expression in the roots, young leaves, and petioles of birch plants. Overexpression of BpMYB95 significantly improved salt-induced browning and wilting symptoms in birch leaves and alleviated the degree of PSII photoinhibition caused by salt stress in birch seedlings. In conclusion, most R2R3-MYB-TFs found in birch were involved in the salt stress response mechanisms. Among these, BpMYB95 was a key regulatory factor that significantly enhanced salt tolerance in birch. The findings of this study provide valuable genetic resources for the development of salt-tolerant birch varieties.
成髓细胞瘤（MYB）转录因子（TF）家族是植物中最大的转录因子家族之一，在各种生理过程中发挥着重要作用。目前，关于桦木（Betula platyphylla Suk.）的 R2R3-MYB-TFs 报道较少，大多数 BpMYBs 仍需要进行特征描述。在这项研究中，鉴定出了 111 个具有保守 R2 和 R3 MYB 结构域的 R2R3-MYB-TFs。系统发育树分析表明，拟南芥和桦木的 MYB 家族成员分别分为 23 和 21 个亚组，后者在 14 条染色体上不均匀分布。在 BpMYBs 之间发生了 5 次串联重复事件和 17 次片段重复事件，重复事件在家族的扩展中起着重要作用。此外，MYB 的启动子区域富含各种顺式作用元件，MYB-TFs 参与植物的生长发育、光响应、生物胁迫和非生物胁迫。RNA-seq 和定量实时聚合酶链反应（qRT-PCR）结果表明，桦木中的大多数 R2R3-MYB-TFs 对盐胁迫有反应。特别是，S20 亚家族的 BpMYBs 对盐、干旱、脱落酸和茉莉酸甲酯胁迫的表达明显诱导。基于桦木在盐胁迫下的生理和 RNA-seq 数据的加权共表达网络分析，鉴定出了一个关键的 MYB-TF BpMYB95（BPChr12G24087），它对盐胁迫有反应，其表达水平受盐胁迫诱导。BpMYB95 是一种核定位蛋白，在酵母中有转录激活活性，过表达该基因可显著提高酿酒酵母的耐盐性。qRT-PCR 和组织化学染色结果表明，BpMYB95 在桦木植物的根、幼叶和叶柄中表达最高。过表达 BpMYB95 可显著改善桦木叶的盐诱导褐变和萎蔫症状，并减轻盐胁迫对桦木叶二磷酸合成酶（PSII）光抑制的程度。综上所述，在桦木中发现的大多数 R2R3-MYB-TFs 参与了盐胁迫反应机制。其中，BpMYB95 是一个关键的调节因子，可显著提高桦木的耐盐性。本研究为培育耐盐桦木品种提供了有价值的遗传资源。
