Spatial distribution of transcript changes in the maize primary root elongation zone at low water potential
1 Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA
2 Department of Animal Science, University of Arizona, Tucson, Arizona 85721, USA
3 Department of Computer Science, University of Missouri, Columbia, MO 65211, USA
4 Department of Plant Biology and Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
5 W. M. Keck Center for Comparative and Functional Genomics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
6 Donald Danforth Plant Science Center, St. Louis, Missouri 63132, USA
7 School of Biotechnology, Yeungnam University, Gyeongsan, Gyeongbuk, 712749 South Korea
8 Research Support Computing, University of Missouri, Columbia, MO 65211, USA
9 Bio-Rad Laboratories, 2000 Alfred Nobel Drive, Hercules, CA 94547, USA
10 School of Biotechnology, Yeungnam University, Gyeongsan, Gyeongbuk, 712749 South Korea
11 Insightful Corporation, Seattle, WA 98109, USA
BMC Plant Biology 2008, 8:32 doi:10.1186/1471-2229-8-32Published: 3 April 2008
Previous work showed that the maize primary root adapts to low Ψw (-1.6 MPa) by maintaining longitudinal expansion in the apical 3 mm (region 1), whereas in the adjacent 4 mm (region 2) longitudinal expansion reaches a maximum in well-watered roots but is progressively inhibited at low Ψw. To identify mechanisms that determine these responses to low Ψw, transcript expression was profiled in these regions of water-stressed and well-watered roots. In addition, comparison between region 2 of water-stressed roots and the zone of growth deceleration in well-watered roots (region 3) distinguished stress-responsive genes in region 2 from those involved in cell maturation.
Responses of gene expression to water stress in regions 1 and 2 were largely distinct. The largest functional categories of differentially expressed transcripts were reactive oxygen species and carbon metabolism in region 1, and membrane transport in region 2. Transcripts controlling sucrose hydrolysis distinguished well-watered and water-stressed states (invertase vs. sucrose synthase), and changes in expression of transcripts for starch synthesis indicated further alteration in carbon metabolism under water deficit. A role for inositols in the stress response was suggested, as was control of proline metabolism. Increased expression of transcripts for wall-loosening proteins in region 1, and for elements of ABA and ethylene signaling were also indicated in the response to water deficit.
The analysis indicates that fundamentally different signaling and metabolic response mechanisms are involved in the response to water stress in different regions of the maize primary root elongation zone.