College of Life Sciences, North China University of Science and Technology, Tangshan, 063210, Hebei, China.
BMC Genomics. 2022 Aug 8;23(1):568. doi: 10.1186/s12864-022-08810-3.
Brassinosteroids (BRs) are a group of essential steroid hormones involved in diverse developmental and physiological processes in plants. The Brassinazole-resistant 1 (BZR1) transcription factors are key components of BR signaling and integrate a wide range of internal and environmental signals to coordinate plant development, growth, and resistance to abiotic and biotic stresses. Although the BZR1 family has been fully studied in Arabidopsis, celery BZR1 family genes remain largely unknown.
Nine BZR1 genes were identified in the celery genome, and categorized into four classes based on phylogenetic and gene structure analyses. All the BZR1 proteins shared a typical bHLH (basic helix-loop-helix) domain that is highly conserved across the whole family in Arabidopsis, grape, lettuce, ginseng, and three Apiaceae species. Both duplications and losses of the BZR1 gene family were detected during the shaping of the celery genome. Whole-genome duplication (WGD) or segmental duplication contributed 55.56% of the BZR1 genes expansion, and the γ as well as celery-ω polyploidization events made a considerable contribution to the production of the BZR1 paralogs in celery. Four AgBZR1 members (AgBZR1.1, AgBZR1.3, AgBZR1.5, and AgBZR1.9), which were localized both in the nucleus and cytoplasm, exhibit transcription activation activity in yeast. AgBZR1.5 overexpression transgenic plants in Arabidopsis showed curled leaves with bent, long petioles and constitutive BR-responsive phenotypes. Furthermore, the AgBZR1 genes possessed divergent expression patterns with some overlaps in roots, petioles, and leaves, suggesting an extensive involvement of AgBZR1s in the developmental processes in celery with both functional redundancy and divergence.
Our results not only demonstrated that AgBZR1 played a conserved role in BR signaling but also suggested that AgBZR1 might be extensively involved in plant developmental processes in celery. The findings lay the foundation for further study on the molecular mechanism of the AgBZR1s in regulating the agronomic traits and environmental adaptation of celery, and provide insights for future BR-related genetic breeding of celery and other Apiaceae crops.
油菜素内酯（BRs）是一组植物中参与多种发育和生理过程的必需甾体激素。油菜素内酯不敏感 1（BZR1）转录因子是 BR 信号转导的关键组成部分，可整合广泛的内部和环境信号，协调植物发育、生长以及对非生物和生物胁迫的抗性。尽管拟南芥中的 BZR1 家族已被充分研究，但芹菜 BZR1 家族基因仍知之甚少。
在芹菜基因组中鉴定出 9 个 BZR1 基因，并根据系统发育和基因结构分析将其分为四个类群。所有 BZR1 蛋白均共享一个典型的 bHLH（碱性螺旋-环-螺旋）结构域，该结构域在整个拟南芥、葡萄、生菜、人参和 3 种伞形科物种的整个家族中高度保守。在芹菜基因组形成过程中，BZR1 基因家族发生了倍增和缺失。全基因组复制（WGD）或片段复制导致 55.56%的 BZR1 基因扩张，γ和芹菜-ω多倍体化事件对芹菜 BZR1 基因的产生做出了巨大贡献。4 个 AgBZR1 成员（AgBZR1.1、AgBZR1.3、AgBZR1.5 和 AgBZR1.9），它们在酵母中定位于细胞核和细胞质中，具有转录激活活性。在拟南芥中过表达 AgBZR1.5 的转基因植物表现出卷曲的叶子，叶柄弯曲，长，并且表现出组成型 BR 响应表型。此外，AgBZR1 基因在根、叶柄和叶片中表现出不同的表达模式，有些重叠，表明 AgBZR1s 在芹菜的发育过程中广泛参与，具有功能冗余和分化。
我们的研究结果不仅表明 AgBZR1 在 BR 信号转导中发挥保守作用，而且还表明 AgBZR1 可能广泛参与芹菜的植物发育过程。这些发现为进一步研究 AgBZR1 调节芹菜农艺性状和环境适应性的分子机制奠定了基础，为未来芹菜和其他伞形科作物的 BR 相关遗传育种提供了依据。
