Research article

Spatial distribution of transcript changes in the maize primary root elongation zone at low water potential

William G Spollen^1,8 , Wenjing Tao^1,9 , Babu Valliyodan¹ , Kegui Chen¹ , Lindsey G Hejlek¹ , Jong-Joo Kim^2,7,10 , Mary E LeNoble¹ , Jinming Zhu¹ , Hans J Bohnert^4,5 , David Henderson^2,11 , Daniel P Schachtman⁶ , Georgia E Davis¹ , Gordon K Springer³ , Robert E Sharp¹ and Henry T Nguyen¹

¹Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA

²Department of Animal Science, University of Arizona, Tucson, Arizona 85721, USA

³Department of Computer Science, University of Missouri, Columbia, MO 65211, USA

⁴Department of Plant Biology and Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA

⁵W. M. Keck Center for Comparative and Functional Genomics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA

⁶Donald Danforth Plant Science Center, St. Louis, Missouri 63132, USA

⁷School of Biotechnology, Yeungnam University, Gyeongsan, Gyeongbuk, 712749 South Korea

⁸Research Support Computing, University of Missouri, Columbia, MO 65211, USA

⁹Bio-Rad Laboratories, 2000 Alfred Nobel Drive, Hercules, CA 94547, USA

¹⁰School of Biotechnology, Yeungnam University, Gyeongsan, Gyeongbuk, 712749 South Korea

¹¹Insightful Corporation, Seattle, WA 98109, USA

author email corresponding author email

BMC Plant Biology 2008, 8:32doi:10.1186/1471-2229-8-32

Published:	3 April 2008

Abstract

Background

Previous work showed that the maize primary root adapts to low Ψ_w (-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 Ψ_w. To identify mechanisms that determine these responses to low Ψ_w, 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.

Results

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.

Conclusion

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.