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Title: Stomatal Function Requires Pectin De-methyl-esterification of the Guard Cell Wall

Stomatal opening and closure depends on changes in turgor pressure acting within guard cells to alter cell shape. The extent of these shape changes is limited by the mechanical properties of the cells, which will be largely dependent on the structure of the cell walls. Although it has long been observed that guard cells are anisotropic due to differential thickening and the orientation of cellulose microfibrils, our understanding of the composition of the cell wall that allows them to undergo repeated swelling and deflation remains surprisingly poor. Here, we show that the walls of guard cells are rich in un-esterified pectins. We identify a pectin methylesterase gene, PME6, which is highly expressed in guard cells and required for stomatal function. pme6-1 mutant guard cells have walls enriched in methyl-esterified pectin and show a decreased dynamic range in response to triggers of stomatal opening/closure, including elevated osmoticum, suggesting that abrogation of stomatal function reflects a mechanical change in the guard cell wall. Altered stomatal function leads to increased conductance and evaporative cooling, as well as decreased plant growth. The growth defect of the  pme6-1 mutant is rescued by maintaining the plants in elevated CO 2, substantiating gas exchange analyses, indicating that the mutant stomata can bestowmore » an improved assimilation rate. Restoration of PME6 rescues guard cell wall pectin methyl-esterification status, stomatal function, and plant growth. Our results establish a link between gene expression in guard cells and their cell wall properties, with a corresponding effect on stomatal function and plant physiology.« less
 [1] ;  [1] ;  [2] ;  [1] ;  [1] ;  [3] ;  [3] ;  [4] ;  [1] ;  [1]
  1. Univ. of Sheffield, Sheffield (United Kingdom)
  2. Univ. of Sheffield, Sheffield (United Kingdom); Univ. of Omar Al-Mukhtar, Al-Baida (Libya)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Univ. of Leeds, Leeds (United Kingdom)
Publication Date:
Grant/Contract Number:
Published Article
Journal Name:
Current Biology
Additional Journal Information:
Journal Volume: 26; Journal Issue: 21; Journal ID: ISSN 0960-9822
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
59 BASIC BIOLOGICAL SCIENCES; stomata; guard cell; cell wall; pectin; Arabidopsis
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1377573