CONSTANS (CO), a well-known member of B-box (BBX) family, is the main component of the photoperiodic regulating flowering and circadian pathways in Arabidopsis (Arabidopsis thaliana). CO is expressed in multiple tissues, including seedling roots and young leaves. However, the roles and underlying mechanisms of CO in modulating physiological processes outside of flowering remains unclear.  

In a study published in Plant Physiology, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) showed that CONSTANS protein negatively modulated salinity tolerance in Arabidopsis through physically associating with and antagonizing the ABSCISIC ACID-RESPONSIVE ELEMENT BINDING FACTOR (ABF) transcription factors under long-day conditions. 

The researchers firstly analyzed spatial pattern of CO expression and detected its transcripts in young leaves and seedling roots. They observed that the CO transcription and proteins levels decreased in seedlings treated with salt stress.  

They then carried out phenotypic analyses and found that CO negatively mediated salinity tolerance under long day (LD) conditions. The loss-of-function co mutant seedlings were more tolerant to salinity stress, whereas overexpression of CO resulted in plants with decreased tolerance to salinity stress. 

Genetic analyses revealed the negative implication of GIGANTEA (GI) in mediating salinity tolerance required a functional CO protein. Further investigations showed that CO physically interacted with the ABSCISIC ACID-RESPONSIVE ELEMENT BINDING  FACTOR1 (ABF1), ABF2, ABF3, and ABF4, which belong to a large basic leucine  zipper (bZIP) domain family. Those ABFs were positively involved in the modulation of salinity tolerance. CO repressed the expression of several salinity-responsive genes and interfered with the transcriptional regulation function of ABF3. 

"Our findings indicate that CO interacts antagonistically with ABFs to inhibit salinity responses. Our study provides a mechanistic understanding of how plant salinity tolerance is negatively regulated by CO functioning in conjunction with ABFs transcription factors," said HU Yanru of XTBG.   

Contact 

HU Yanru   Ph.D Principal Investigator 

Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, Yunnan, China                       

E-mail:  huyanru@xtbg.ac.cn     

Published: 28 June 2023