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Restricted cell elongation in Arabidopsis hypocotyls is associated with a reduced average pectin esterification level.

Derbyshire P, McCann MC, Roberts K - BMC Plant Biol. (2007)

Bottom Line: We present evidence that the degree of pectin methyl-esterification (DE%) limits cell growth, and that a minimum level of about 60% DE is required for normal cell elongation in Arabidopsis hypocotyls.Low average levels of pectin DE% are associated with reduced cell elongation, implicating PMEs, the enzymes that regulate DE%, in the cell elongation process and in responses to GA.At high average DE% other components of the cell wall limit GA-induced growth.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Metabolic Biology, John Innes Centre, Norwich, UK. paul.derbyshire@bbsrc.ac.uk

ABSTRACT

Background: Cell elongation is mainly limited by the extensibility of the cell wall. Dicotyledonous primary (growing) cell walls contain cellulose, xyloglucan, pectin and proteins, but little is known about how each polymer class contributes to the cell wall mechanical properties that control extensibility.

Results: We present evidence that the degree of pectin methyl-esterification (DE%) limits cell growth, and that a minimum level of about 60% DE is required for normal cell elongation in Arabidopsis hypocotyls. When the average DE% falls below this level, as in two gibberellic acid (GA) mutants ga1-3 and gai, and plants expressing pectin methyl-esterase (PME1) from Aspergillus aculeatus, then hypocotyl elongation is reduced.

Conclusion: Low average levels of pectin DE% are associated with reduced cell elongation, implicating PMEs, the enzymes that regulate DE%, in the cell elongation process and in responses to GA. At high average DE% other components of the cell wall limit GA-induced growth.

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Growth kinetics and hypocotyl cell elongation in P5-3, PME01, and PME08 seedlings. Seedlings were grown in continuous light for 10 d with plates in a near vertical position and hypocotyl growth measured over this period. Measurements are an average taken from 12 to 20 seedlings ± SE for each time point. After 3 d seedlings were transferred to control medium, or induction medium containing 0.1% (v/v) ethanol. Arrows indicate time (5 d) at which hypocotyls were further analysed. (A) P5-3, (B) PME01, (C) PME08.
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Figure 3: Growth kinetics and hypocotyl cell elongation in P5-3, PME01, and PME08 seedlings. Seedlings were grown in continuous light for 10 d with plates in a near vertical position and hypocotyl growth measured over this period. Measurements are an average taken from 12 to 20 seedlings ± SE for each time point. After 3 d seedlings were transferred to control medium, or induction medium containing 0.1% (v/v) ethanol. Arrows indicate time (5 d) at which hypocotyls were further analysed. (A) P5-3, (B) PME01, (C) PME08.

Mentions: Hypocotyl growth kinetics are shown in Figure 3. In the absence of ethanol, P5-3 hypocotyls grew over a period of 6 d, from day 2 to day 8, with a final length of 5.56 ± 0.17 mm (Figure 3A). The concentration of ethanol used to induce PME1 expression did not affect either the growth profile or final length of P5-3 hypocotyls, which measured 5.77 ± 0.29 mm at day 10. However, compared to previous experiments (Figure 1A), the duration and extent of hypocotyl elongation was increased when plates were positioned vertically, and may be the result of additional nutrient uptake and/or touch responses from being in contact with the surface of the growing medium. In the absence of ethanol, both PME01 and PME08 hypocotyls followed a similar growth profile as P5-3. Final lengths were 5.67 ± 0.22 and 5.25 ± 0.21 mm in lines PME01 and PME08, respectively (Figure 3B, C). However, transfer of the seedlings to induction medium resulted in a deflection of the growth curve for both expressing lines. Hypocotyls stopped growing about 1 d earlier, and final lengths were 4.63 ± 0.24 and 4.27 ± 0.23 mm, respectively, representing a length reduction of about 20%.


Restricted cell elongation in Arabidopsis hypocotyls is associated with a reduced average pectin esterification level.

Derbyshire P, McCann MC, Roberts K - BMC Plant Biol. (2007)

Growth kinetics and hypocotyl cell elongation in P5-3, PME01, and PME08 seedlings. Seedlings were grown in continuous light for 10 d with plates in a near vertical position and hypocotyl growth measured over this period. Measurements are an average taken from 12 to 20 seedlings ± SE for each time point. After 3 d seedlings were transferred to control medium, or induction medium containing 0.1% (v/v) ethanol. Arrows indicate time (5 d) at which hypocotyls were further analysed. (A) P5-3, (B) PME01, (C) PME08.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1913053&req=5

Figure 3: Growth kinetics and hypocotyl cell elongation in P5-3, PME01, and PME08 seedlings. Seedlings were grown in continuous light for 10 d with plates in a near vertical position and hypocotyl growth measured over this period. Measurements are an average taken from 12 to 20 seedlings ± SE for each time point. After 3 d seedlings were transferred to control medium, or induction medium containing 0.1% (v/v) ethanol. Arrows indicate time (5 d) at which hypocotyls were further analysed. (A) P5-3, (B) PME01, (C) PME08.
Mentions: Hypocotyl growth kinetics are shown in Figure 3. In the absence of ethanol, P5-3 hypocotyls grew over a period of 6 d, from day 2 to day 8, with a final length of 5.56 ± 0.17 mm (Figure 3A). The concentration of ethanol used to induce PME1 expression did not affect either the growth profile or final length of P5-3 hypocotyls, which measured 5.77 ± 0.29 mm at day 10. However, compared to previous experiments (Figure 1A), the duration and extent of hypocotyl elongation was increased when plates were positioned vertically, and may be the result of additional nutrient uptake and/or touch responses from being in contact with the surface of the growing medium. In the absence of ethanol, both PME01 and PME08 hypocotyls followed a similar growth profile as P5-3. Final lengths were 5.67 ± 0.22 and 5.25 ± 0.21 mm in lines PME01 and PME08, respectively (Figure 3B, C). However, transfer of the seedlings to induction medium resulted in a deflection of the growth curve for both expressing lines. Hypocotyls stopped growing about 1 d earlier, and final lengths were 4.63 ± 0.24 and 4.27 ± 0.23 mm, respectively, representing a length reduction of about 20%.

Bottom Line: We present evidence that the degree of pectin methyl-esterification (DE%) limits cell growth, and that a minimum level of about 60% DE is required for normal cell elongation in Arabidopsis hypocotyls.Low average levels of pectin DE% are associated with reduced cell elongation, implicating PMEs, the enzymes that regulate DE%, in the cell elongation process and in responses to GA.At high average DE% other components of the cell wall limit GA-induced growth.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Metabolic Biology, John Innes Centre, Norwich, UK. paul.derbyshire@bbsrc.ac.uk

ABSTRACT

Background: Cell elongation is mainly limited by the extensibility of the cell wall. Dicotyledonous primary (growing) cell walls contain cellulose, xyloglucan, pectin and proteins, but little is known about how each polymer class contributes to the cell wall mechanical properties that control extensibility.

Results: We present evidence that the degree of pectin methyl-esterification (DE%) limits cell growth, and that a minimum level of about 60% DE is required for normal cell elongation in Arabidopsis hypocotyls. When the average DE% falls below this level, as in two gibberellic acid (GA) mutants ga1-3 and gai, and plants expressing pectin methyl-esterase (PME1) from Aspergillus aculeatus, then hypocotyl elongation is reduced.

Conclusion: Low average levels of pectin DE% are associated with reduced cell elongation, implicating PMEs, the enzymes that regulate DE%, in the cell elongation process and in responses to GA. At high average DE% other components of the cell wall limit GA-induced growth.

Show MeSH
Related in: MedlinePlus