AN HMA DOMAIN-CONTAINING PROTEIN NaKR1 REGULATES LONG-DISTANCE FLORIGEN MOVEMENT IN ARABIDOPSIS THALIANA

Abstract

PLANTS PERCEIVE SEASONAL CHANGES IN DAY LENGTH IN LEAVES AND CONSEQUENTIALLY TRIGGER LONG-DISTANCE SIGNALING TO INDUCE FLOWERING AT THE SHOOT APEX. IN A. THALIANA, PART OF THE MOBILE FLOWERING SIGNALS CALLED FLORIGEN HAS BEEN IDENTIFIED AS THE FLOWERING LOCUS T (FT) PROTEIN, WHICH IS INDUCED BY THE NUCLEAR PROTEIN CONSTANS (CO) IN RESPONSE TO LONG-DAY (LD) CONDITIONS. HERE WE REPORT THAT A HEAVY-METAL-ASSOCIATED (HMA) DOMAIN-CONTAINING PROTEIN, SODIUM POTASSIUM ROOT DEFECTIVE1 (NAKR1), IS ALSO INDUCED BY CO UNDER LDS, AND PLAYS AN IMPORTANT ROLE IN FT TRANSPORTATION. LOSS OF FUNCTION OF NAKR1 RESULTS IN EXTREMELY LATE FLOWERING ONLY UNDER LDS. FURTHERMORE, NAKR1 SHARES SIMILAR MRNA EXPRESSION AND PROTEIN SUBCELLULAR LOCALIZATION PATTERNS WITH FT, AND IT ALSO INTERACTS WITH FT IN PLANTA. FINALLY, WE DEMONSTRATE THAT NAKR1 ACTS AS A CHAPERONE REQUIRED FOR FT LONG-DISTANCE MOVEMENT FROM THE LEAF VASCULATURE TO THE APEX BETWEEN DONOR AND RECIPIENT PLANTS. THESE RESULTS SUGGEST THAT NAKR1 I