CmoNAC1's key role in grafted cucumbers revealed salt tolerance in crops

Soil salinity, impacting about one billion square hectometers worldwide, significantly hinders crop growth. Plants counteract this through signaling pathways involving molecules such as H₂O₂ and ABA. NAC transcription factors, which are unique to plants, play a central role in the regulation of these stress responses. In grafted vegetables, such as cucumbers on pumpkin rootstocks, these factors seem crucial for enhancing salt tolerance by modulating stomatal closure. However, the detailed regulatory role of NAC factors in this context remains unclear, highlighting a vital area for research.

In July 2023, Horticulture Research published a research entitled by “CmoNAC1 in pumpkin rootstocks improves salt tolerance of grafted cucumbers by binding to the promoters of CmoRBOHD1, CmoNCED6, CmoAKT1;2 and CmoHKT1;1 to regulate H₂O₂, ABA signaling and K+/Na+ homeostasis”. This study provides new insights into improving salt tolerance in cucumbers and valuable references for molecular breeding of salt tolerant pumpkin rootstocks.

Initially, homologs of the enzyme NCED were identified in pumpkin, with CmoNCED6 emerging as the key gene for ABA synthesis under salt stress. The analysis of transcription factors binding to the promoters of CmoRBOHD1 and CmoNCED6 identified CmoNAC1 as a significant regulator. Root transformation experiments demonstrated that CmoNAC1 knockout resulted in decreased H₂O₂, ABA content, and K+/Na+ ratio in grafted cucumbers, while overexpression had the opposite effect, confirming CmoNAC1's role in enhancing salt tolerance.  Further research has shown that CmoNAC1 affects the production of H₂O₂ and ABA in grafted cucumber leaves and roots by regulating the expression of CsaRBOHD, CsaNCED3, CmoRBOHD1, and CmoNCED6, thereby regulating physiological responses under salt stress.

In addition, this study validated the important role of CmoNCED6 in salt tolerance of grafted cucumbers, particularly in influencing ABA signal transduction, stomatal regulation, and ion balance regulation. CmoNAC1 can bind to the promoters of CmoRBOHD1, CmoNCED6, CmoAKT1;2, and CmoHKT1;1, thereby regulating their expression. This binding was confirmed using yeast one-hybrid, luciferase, and electrophoretic mobility shift assays. The regulatory effect of CmoNAC1 on K+/Na+ transporters under salt stress was also established, showing that knockout and overexpression of CmoNAC1 significantly altered the expression of key transporters.

In conclusion, this research demonstrated that CmoNAC1 is a pivotal transcription factor in grafted cucumbers, contributing to salt tolerance by regulating H₂O₂ and ABA signaling and K+/Na+ homeostasis. This discovery adds valuable knowledge to the field of plant biology and agricultural practices, particularly in the context of enhancing crop resilience to environmental stressors such as soil salinity.

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References

Authors

Yuquan Peng¹, Haishun Cao^1,2, Lvjun Cui¹, Ying Wang¹, Lanxing Wei¹, Shouyu Geng¹, Li Yang¹, Yuan Huang^1,*, and Zhilong Bie^1,3,*

Affiliations

¹National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops/College of Horticulture and Forestry Sciences, Huazhong Agricultural University, 430070 Wuhan, China

²Institute of Facility Agriculture, Guangdong Academy of Agricultural Sciences, 510640 Guangzhou, China

³Hubei Hongshan Laboratory, 430070 Wuhan, China

About Zhilong Bie

He is a professor in the College of Horticulture and Forestry Sciences at Huazhong Agricultural University. His research interests include vegetable and watermelon facility cultivation and growth and development regulation, and vegetable adversity physiology and molecular biology.