Present address: Department of Biology, Wake Forest University, 1834 Wake Forest Road, Winston-Salem, NC 27109, USA.
Auxin transport into cotyledons and cotyledon growth depend similarly on the ABCB19 Multidrug Resistance-like transporter
Article first published online: 29 JUN 2009
© 2009 The Authors. Journal compilation © 2009 Blackwell Publishing Ltd
The Plant Journal
Volume 60, Issue 1, pages 91–101, October 2009
How to Cite
Lewis, D. R., Wu, G., Ljung, K. and Spalding, E. P. (2009), Auxin transport into cotyledons and cotyledon growth depend similarly on the ABCB19 Multidrug Resistance-like transporter. The Plant Journal, 60: 91–101. doi: 10.1111/j.1365-313X.2009.03941.x
- Issue published online: 24 SEP 2009
- Article first published online: 29 JUN 2009
- Received 10 March 2009; revised 13 May 2009; accepted 18 May 2009; published online 29 June 2009.
ABCB19 of Arabidopsis thaliana (formerly known as MDR1 and PGP19) belongs to the Multidrug Resistance-like (MDR) or B group of the ATP-binding cassette (ABC) transporter superfamily, and mediates polar auxin transport in stems and roots. Here we have investigated the role of ABCB19 and auxin distribution in cotyledon development. During embryogenesis, confocal microscopy showed ABCB19 protein to be present in cotyledons during their main growth phase, but not later. Analysis of ProDR5:GFP expression patterns showed a significantly diminished and restricted auxin distribution pattern in abcb19 cotyledons. Nonetheless, development of abcb19 embryonic cotyledons was very similar to that of wild-type. Post-germination, ABCB19 was present in the plasma membrane of cotyledon epidermal, mesophyll and petiole cells during blade expansion. Post-germination cotyledon blade expansion in abcb19 was 65% slower than in wild-type, although the epidermal cell area was reduced by only 17%. The growth rate reduction quantitatively correlated with reduced auxin levels rather than auxin sensitivity as indicated by quantitative ProDR5:GUS assays and direct auxin measurements, and may be explained by the 50% reduction in the import of auxin through the petioles of abcb19 cotyledons during the period of maximum expansion. Taken together, these data indicate that cotyledon expansion during the establishment of photoautotrophic growth depends on ABCB19-mediated auxin import.