成髓细胞病(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,关于桦树的报道很少(白桦。)的R2R3-MYB-TFs,大多数BpMYB仍然需要表征。在这项研究中,鉴定了111个具有保守的R2和R3MYB结构域的R2R3-MYB-TF。系统发育树分析表明拟南芥和桦树MYB家族成员分为23个和21个亚组,分别。后者在14条染色体上表现出不均匀分布。BpMYB之间有5个串联重复事件和17个节段重复事件,重复事件在家庭的扩张中起着重要作用。此外,MYBs的启动子区富含各种顺式作用元件,MYB-TFs参与植物的生长发育,光的反应,生物应激,和非生物胁迫。RNA测序(RNA-seq)和定量实时聚合酶链反应(qRT-PCR)结果表明,桦树中的大多数R2R3-MYB-TF对盐胁迫有反应。特别是,盐显著诱导S20亚家族中BpMYBs的表达,干旱,脱落酸,和茉莉酸甲酯应力。基于盐胁迫下桦树生理和RNA-seq数据的加权共表达网络分析,一个关键的MYB-TFBpMYB95(BPCr12G24087),被鉴定为对盐胁迫的反应,其表达水平受盐胁迫诱导。BpMYB95是一种在酵母中具有转录激活活性的核定位蛋白,该基因的过表达显着增强了酿酒酵母的耐盐性。qRT-PCR和组织化学染色结果显示,BpMYB95在根中表达量最高,幼叶,和桦树植物的叶柄。过表达BpMYB95显著改善了盐诱导的桦树叶片褐变和萎萎症状,减轻了盐胁迫对桦树幼苗的PSII光抑制程度。总之,在桦树中发现的大多数R2R3-MYB-TF都参与了盐胁迫响应机制。其中,BpMYB95是显著增强桦树耐盐性的关键调控因子。本研究结果为耐盐桦树品种的开发提供了宝贵的遗传资源。
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.