Function of ABCBs in Light Signaling

Light signaling controls the growth and development of plants through regulating gene expression and the action of phytohormones including auxin. Among 21 full-size ATP-binding cassette protein subfamily B (ABCB) genes in the Arabidopsis thaliana genome, ABCB19/PGP19/MDR1 (P-GLYCOPROTEIN19/MULTIDRUG RESISTANCE1) and its closest homolog ABCB1/PGP1 encode auxin transporters, and these functions have been well studied in the light responses of plants. They are involved not only in photomorphogenesis including inhibition of hypocotyl elongation and apical hook opening but also in photomovements including phototropic responses and light-induced randomization of hypocotyl growth orientation. Here, we review the functional regulation of ABCB19 by light signaling, and then discuss the functions of ABCB19 and ABCB1 for each light response.