Combining Physiology and Transcriptome to Reveal Mechanisms of 'Golden Cadet' in Response to Alkali Stress.

As an ornamentally and medicinally worthy plant, (Lam.) Aschers. has the adapted capacity to survive cold temperate monsoon climates in Northeastern China. However, its use is limited by the soil alkalization of urban gardens. Our pre-experiment found that 'Golden Cadet' has the potential to be alkali-tolerant. Hence, tissue-cultured seedlings of 'Golden Cadet' were used as experimental material. Its related growth, physiology, and transcripts were examined to reveal the molecular mechanism of in response to alkali stress. The results show that the development of 'Golden Cadet' was affected by alkali stress. In comparison with the control, malondialdehyde (MDA) content increased by 4.28-fold at the 24th hour, superoxide dismutase (SOD) activity increased by 49% at the 6th hour, and peroxidase (POD) activity and soluble sugar (SS) content increased by 67% and 30% at the 12th hour, respectively. The RNA-seq analysis revealed that 'Golden Cadet' gene expressions at 0 h, 6 h, 12 h, 21 h and 48 h differed after 200 mmol/L NaHCO treatment. During 48 h under alkali stress, 2366 differentially expressed genes were found. The transcription factors MYB, AP2/ERF, and WRKY were activated in differentially expressed genes. The KEGG analysis found that phytohormone signaling pathways, starch and sucrose metabolism, and phenylpropane production were activated in 'Golden Cadet' in response to alkali stress. In summary, 'Golden Cadet' can reduce membrane damage by improving osmoregulation and antioxidant capacity, increase sucrose and starch metabolism, and regulate phenylpropane biosynthesis by activating transcription factors and inducing related phytohormone signaling, mitigating the effects of alkali toxicity. These findings guide an investigation into the mechanism of alkali tolerance in plants, screening alkali tolerance genes, and selecting and breeding novel alkali-tolerant cultivars.