A role for ABCB19-mediated polar auxin transport in seedling photomorphogenesis mediated by cryptochrome 1 and phytochrome B
Article first published online: 18 JAN 2010
© 2010 The Authors. Journal compilation © 2010 Blackwell Publishing Ltd
The Plant Journal
Volume 62, Issue 2, pages 179–191, April 2010
How to Cite
Wu, G., Cameron, J. N., Ljung, K. and Spalding, E. P. (2010), A role for ABCB19-mediated polar auxin transport in seedling photomorphogenesis mediated by cryptochrome 1 and phytochrome B. The Plant Journal, 62: 179–191. doi: 10.1111/j.1365-313X.2010.04137.x
- Issue published online: 21 APR 2010
- Article first published online: 18 JAN 2010
- Received 5 November 2009; revised 4 December 2009; accepted 16 December 2009; published online 3 March 2010.
- auxin transport;
- hypocotyl growth;
During seedling establishment, blue and red light suppress hypocotyl growth through the cryptochrome 1 (cry1) and phytochrome B (phyB) photosensory pathways, respectively. How these photosensory pathways integrate with growth control mechanisms to achieve the appropriate degree of stem elongation was investigated by combining cry1 and phyB photoreceptor mutations with genetic manipulations of a multidrug resistance-like membrane protein known as ABCB19 that influenced auxin distribution within the plant, as evidenced by a combination of reporter gene assays and direct auxin measurements. Auxin signaling and ABCB19 protein levels, hypocotyl growth rates, and apical hook opening were measured in mutant and wild-type seedlings exposed to a range of red and blue light conditions. Ectopic/overexpression of ABCB19 (B19OE) greatly increased auxin in the hypocotyl, which reduced the sensitivity of hypocotyl growth specifically to blue light in long-term assays and red light in high-resolution, short-term assays. Loss of ABCB19 partially suppressed the cry1 hypocotyl growth phenotype in blue light. Hypocotyl growth of B19OE seedlings in red light was very similar to phyB mutants. Altered auxin distribution in B19OE seedlings also affected the opening of the apical hook. The cry1 and phyB photoreceptor mutations both increased ABCB19 protein levels at the plasma membrane, as measured by confocal microscopy. The B19OE plant proved to be a useful tool for determining aspects of the mechanism by which light, acting through cry1 or phyB, influences the auxin transport process to control hypocotyl growth during de-etiolation.