Plant roots can sense the nitrogen level in the environment and change the expression of related genes to maintain normal life activities. However, their regulatory mechanism in Chrysanthemum has not been fully clarified. In this study, an R2R3-MYB transcription factor CmMYB42 was isolated from Chrysanthemum ‘Jinba.’ Tissue expression analysis showed that the gene was mainly expressed in the root and could rapidly up-regulate the expression of CmMYB42 under low-nitrogen conditions. Subcellular localization analysis showed that CmMYB42 was located in the nucleus. Under low-nitrogen stress, overexpressing CmMYB42 Chrysanthemum’s total root length, lateral root number, plant height, and biomass accumulation were significantly higher than wild type and slowed down the damage to photosynthetic system and improved NO₃⁻ content and nitrogen metabolism assimilation enzyme activity. In addition, we also found that CmMYB42 increased the expression of nitrogen stress-related genes. These results indicated that CmMYB42 acts as a positive regulator to improve the tolerance of Chrysanthemum to low-nitrogen stress, providing a theoretical basis for further exploring the molecular mechanism of low-nitrogen tolerance in Chrysanthemum.

植物根系可以感知环境中的氮含量，改变相关基因的表达，维持正常的生命活动。然而，它们在菊花中的调控机制尚未完全阐明。在这项研究中，R2R3-MYB 转录因子CmMYB42是从菊花'Jinba' 中分离出来的。组织表达分析表明，该基因主要在根中表达，在低氮条件下能够快速上调CmMYB42的表达。亚细胞定位分析显示CmMYB42定位于细胞核。低氮胁迫下过表达CmMYB42菊花其总根长、侧根数、株高和生物量积累均显着高于野生型，减缓了对光合系统的损害，提高了NO 3 - 含量和_氮^代谢同化酶活性。此外，我们还发现CmMYB42增加了氮胁迫相关基因的表达。这些结果表明CmMYB42作为正调控因子提高菊花对低氮胁迫的耐受性，为进一步探索菊花耐低氮的分子机制提供理论依据。