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Phytochromes and cryptochromes regulate the differential growth of Arabidopsis hypocotyls in both a PGP19‐dependent and a PGP19‐independent manner
Author(s) -
Nagashima Akitomo,
Suzuki Genki,
Uehara Yukiko,
Saji Kensuke,
Furukawa Toshiko,
Koshiba Tomokazu,
Sekimoto Masayo,
Fujioka Shozo,
Kuroha Takeshi,
Kojima Mikiko,
Sakakibara Hitoshi,
Fujisawa Noriko,
Okada Kiyotaka,
Sakai Tatsuya
Publication year - 2008
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2007.03358.x
Subject(s) - hypocotyl , cryptochrome , arabidopsis , auxin , phototropism , gravitropism , phytochrome , microbiology and biotechnology , polar auxin transport , biology , phytochrome a , chemistry , botany , biochemistry , mutant , blue light , gene , materials science , circadian clock , red light , optoelectronics
Summary 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.