Phytochromes and cryptochromes regulate the differential growth of Arabidopsis hypocotyls in both a PGP19-dependent and a PGP19-independent manner.
Photoreceptors, phytochromes and cryptochromes regulate hypocotyl growth under specific conditions, by suppressing negative gravitropism, modulating phototropism and inhibiting elongation. Although these effects seem to be partially caused via the regulation of the phytohormone auxin, the molecular mechanisms underlying this process are still poorly understood. In our present study, we demonstrate that the flabby mutation enhances both phytochrome- and cryptochrome-inducible hypocotyl bending in Arabidopsis. The FLABBY gene encodes the ABC-type auxin transporter, PGP19, and its expression is suppressed by the activation of phytochromes and cryptochromes. Our current results therefore indicate that the phytochromes and cryptochromes have at least two effects upon the tropic responses of the hypocotyls in Arabidopsis: the enhancement of hypocotyl bending through the suppression of PGP19, and a PGP19-independent mechanism that induces hypocotyl bending. By the using an auxin polar transport assay and DR5:GUS expression analysis, we further find that the phytochromes inhibit basipetal auxin transport, and induce the asymmetric distribution of auxin in the hypocotyls. These data suggest that the control of auxin transport by phytochromes and cryptochromes is a critical regulatory component of hypocotyl growth in response to light.
Nagashima
Akitomo
A
RIKEN Plant Science Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230 0045, Japan.
Suzuki
Genki
G
Uehara
Yukiko
Y
Saji
Kensuke
K
Furukawa
Toshiko
T
Koshiba
Tomokazu
T
Sekimoto
Masayo
M
Fujioka
Shozo
S
Kuroha
Takeshi
T
Kojima
Mikiko
M
Sakakibara
Hitoshi
H
Fujisawa
Noriko
N
Okada
Kiyotaka
K
Sakai
Tatsuya
T
D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D001692:Biological Transport; D015152:Blotting, Northern; D015153:Blotting, Western; D056931:Cryptochromes; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism; D008027:Light; D010834:Phytochrome / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
D018528:ATP-Binding Cassette Transporters; D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D005420:Flavoproteins; D007210:Indoleacetic Acids; C519873:PGP19 protein, Arabidopsis; D010834:Phytochrome