Abstract
Brassinosteroids (BRs) play crucial roles in the physiology and development of plants. In the model plant Arabidopsis, BR signaling is initiated at the level of membrane receptors, BRASSINOSTEROIDS INSENSITIVE 1 (BRI1) and BRI1-ASSOCIATED RECEPTOR KINASE 1 (BAK1) complex, thus activating the transcription factors (TFs) BRASSINAZOLE RESISTANT 1/BRI1-EMS-SUPPRESSOR 1 (BZR1/BES1) to coordinate BR responsive genes. BRASSINOSTEROIDS INSENSITIVE 2 (BIN2), glycogen synthase kinase 3 (GSK3) like-kinase, negatively regulates BZR1/BES1 transcriptional activity through phosphorylation-dependent cytosolic retention and shuttling. However, it is still unknown whether this mechanism is conserved in Panax ginseng C. A. Mayer, a member of the Araliaceae family, which is a shade-tolerant perennial root crop. Despite its pharmacological and agricultural importance, the role of BR signaling in the development of P. ginseng and characterization of BR signaling components are still elusive. In this study, by utilizing the Arabidopsis bri1 mutant, we found that ectopic expression of the gain of function form of PgBZR1 (Pgbzr1-1D) restores BR deficiency. In detail, ectopic expression of Pgbzr1-1D rescues dwarfism, defects of floral organ development, and hypocotyl elongation of bri1-5, implying the functional conservation of PgBZR1 in P. ginseng. Interestingly, brassinolide (BL) and BRs biosynthesis inhibitor treatment in two-year-old P. ginseng storage root interferes with and promotes, respectively, secondary growth in terms of xylem formation. Altogether, our results provide new insight into the functional conservation and potential diversification of BR signaling and response in P. ginseng.
Highlights
Brassinosteroids (BRs) are major plant-specific steroid hormones which regulate multiple aspects of growth and development [1,2]
We focused on the major regulators of BR signaling, BRASSINOSTEROID INSENSITIVE 1 (BRI1), BRASSINOSTEROID INSENSITIVE 2 (BIN2), and BRASSINAZOLE-RESISTANT 1 (BZR1)
We characterized components of BR signaling in P. ginseng and the functional role of BR signaling mediated by PgBZR1 from P. ginseng, the perennial medicinal plant belonging to Araliaceae
Summary
Brassinosteroids (BRs) are major plant-specific steroid hormones which regulate multiple aspects of growth and development [1,2]. Among these well-characterized BR signaling components, the atypical basic helix-loop-helix (bHLH) plant-specific transcription factors BES1, BZR1, and BES1/BZR1 homolog 1-4 (BEH1-4) have been identified as key transcriptional regulators of BR signaling in Arabidopsis [22,23,24,25] These members are functionally redundant in the BR response, including a common set of the binding element in DNA (E-box; CANNTG for BR induced gene expression, BRRE; CGTGT/CG for BR repressed gene expression), and tightly controlled by BIN2 at the level of post-translational modification [25,26]. The role of BR signaling during the formation of the storage root, the hidden half of the secondary growth of the plant, has not yet been explored
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
