Dataset Information

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

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

SUBMITTER: Spollen WG

PROVIDER: S-EPMC2364623 | biostudies-literature | 2008 Apr

REPOSITORIES: biostudies-literature

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

Spollen William G WG Tao Wenjing W Valliyodan Babu B Chen Kegui K Hejlek Lindsey G LG Kim Jong-Joo JJ Lenoble Mary E ME Zhu Jinming J Bohnert Hans J HJ Henderson David D Schachtman Daniel P DP Davis Georgia E GE Springer Gordon K GK Sharp Robert E RE Nguyen Henry T HT

BMC plant biology 20080403

<h4>Background</h4>Previous work showed that the maize primary root adapts to low Psiw (-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 Psiw. To identify mechanisms that determine these responses to low Psiw, transcript expression was profiled in these regions of water-stressed and well-watered roots. In addition, comparison b ...[more]

PMID: 18387193

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Project description:Reactive oxygen species (ROS) can act as signaling molecules involved in the acclimation of plants to various abiotic and biotic stresses. However, it is not clear how the generalized increases in ROS and downstream signaling events that occur in response to stressful conditions are coordinated to modify plant growth and development. Previous studies of maize (Zea mays L.) primary root growth under water deficit stress showed that cell elongation is maintained in the apical region of the growth zone but progressively inhibited further from the apex, and that the rate of cell production is also decreased. It was observed that apoplastic ROS, particularly hydrogen peroxide (H2O2), increased specifically in the apical region of the growth zone under water stress, resulting at least partly from increased oxalate oxidase activity in this region. To assess the function of the increase in apoplastic H2O2 in root growth regulation, transgenic maize lines constitutively expressing a wheat oxalate oxidase were utilized in combination with kinematic growth analysis to examine effects of increased apoplastic H2O2 on the spatial pattern of cell elongation and on cell production in well-watered and water-stressed roots. Effects of H2O2 removal (via scavenger pretreatment) specifically from the apical region of the growth zone were also assessed. The results show that apoplastic H2O2 positively modulates cell production and root elongation under well-watered conditions, whereas the normal increase in apoplastic H2O2 in water-stressed roots is causally related to down-regulation of cell production and root growth inhibition. The effects on cell production were accompanied by changes in spatial profiles of cell elongation and in the length of the growth zone. However, effects on overall cell elongation, as reflected in final cell lengths, were minor. These results reveal a fundamental role of apoplastic H2O2 in regulating cell production and root elongation in both well-watered and water-stressed conditions.

Project description:Background and aimsInternal aeration is important for plants to survive during periods of waterlogging, and the ability to form aerenchyma contributes by creating a continuous gas space between the shoots and the roots. Roots of maize (Zea mays) react to prolonged waterlogging by forming aerenchyma in root cortical cells by programmed cell death (PCD) in response to ethylene. The aim of this study was to understand the molecular mechanisms of ethylene-induced aerenchyma formation by identifying genes that are either up- or downregulated by ethylene treatment in maize root cortical cells.MethodsThree-day-old maize seedlings were treated with ethylene for several hours under aerobic conditions. Cortical cells were isolated from the primary roots using laser microdissection (LM), and transcript profiles with and without ethylene treatment were compared by microarray. In addition, the effect on ethylene-induced aerenchyma formation of diphenyleneiodonium (DPI), an inhibitor of NADPH oxidases, was examined in order to assess the involvement of reactive oxygen species (ROS).Key resultsA total of 223 genes were identified whose transcript levels were significantly increased or decreased by ethylene treatment in root cortical cells under aerobic conditions. Subsequent tissue-specific quantitative reverse-transcription PCR analyses revealed that ethylene increased the transcript levels of genes related to ethylene signalling in all of the root tissues examined (stelar cells, cortical cells and outer cell layers), whereas it increased the transcript levels of genes related to cell wall modification and proteolysis specifically in the cortical cells. DPI treatment inhibited the ethylene-induced aerenchyma formation and suppressed expression of some cell wall modification-related genes.ConclusionsSeveral genes related to cell wall modification and proteolysis are specifically up- or downregulated in cortical cells during lysigenous aerenchyma formation under aerobic conditions with ethylene treatment. The results suggest that ethylene is perceived in stelar cells, cortical cells and outer cell layers in the maize primary root, and that the cortical cell-specific PCD is controlled downstream of ethylene perception through subsequent gene expression, which is partly regulated by ROS, in the cortical cells.

Dataset Information

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

Publications

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

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