Limits...
1-Aminocyclopropane-1-carboxylic acid (ACC) concentration and ACC synthase expression in soybean roots, root tips, and soybean cyst nematode (Heterodera glycines)-infected roots.

Tucker ML, Xue P, Yang R - J. Exp. Bot. (2009)

Bottom Line: In addition, an ACS-like sequence was found in the public SCN nucleotide database.Acquisition of a full-length sequence for this mRNA (accession GQ389647) and alignment with transcripts for other well-characterized ACS proteins indicated that the nematode sequence is missing a key element required for ACS activity and therefore probably is not a functional ACS.Moreover, no significant amount of ACC was found in any growth stage of SCN that was tested.

View Article: PubMed Central - PubMed

Affiliation: Soybean Genomics and Improvement Lab, Agricultural Research Service, United States Department of Agriculture, 10300 Baltimore Ave., Beltsville, MD, USA. mark.tucker@ars.usda.gov

ABSTRACT
Colonization of plant roots by root knot and cyst nematodes requires a functional ethylene response pathway. However, ethylene plays many roles in root development and whether its role in nematode colonization is direct or indirect, for example lateral root initiation or root hair growth, is not known. The temporal requirement for ethylene and localized synthesis of ethylene during the life span of soybean cyst nematode (SCN) on soybean roots was further investigated. Although a significant increase in ethylene evolution was not detected from SCN-colonized roots, the concentration of the immediate precursor to ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC), was higher in SCN-colonized root pieces and root tips than in other parts of the root. Moreover, expression analysis of 17 ACC synthase (ACS) genes indicated that a select set of ACS genes is expressed in SCN-colonized root pieces that is clearly different from the set of genes expressed in non-colonized roots or root tips. Semi-quantitative real-time PCR indicated that ACS transcript accumulation correlates with the high concentration of ACC in root tips. In addition, an ACS-like sequence was found in the public SCN nucleotide database. Acquisition of a full-length sequence for this mRNA (accession GQ389647) and alignment with transcripts for other well-characterized ACS proteins indicated that the nematode sequence is missing a key element required for ACS activity and therefore probably is not a functional ACS. Moreover, no significant amount of ACC was found in any growth stage of SCN that was tested.

Show MeSH

Related in: MedlinePlus

Inhibition of ethylene action reduces the numbers of SCNs that develop on soybean roots, and addition of ethylene increases the number. (A) Continuous exposure of SCN-inoculated monoxenic roots to no inhibitors (control), 2 μl l−1 1-MCP, 5000 μl l−1 NBD, or 1 μl l−1 ethylene. (B) Exposure of monoxenic roots to 5000 μl l−1 NBD for 10 d intervals preceded or followed by exposure to air with no inhibitor, or continuous exposure of roots to 5000 μl l−1 NBD for 30 d or to 5000 μl l−1 NBD plus 100 μl l−1 ethylene. (C) Continuous exposure of monoxenic roots to 2000 μl l−1 NBD or 2000 μl l−1 NBD plus 25 μl l−1 ethylene.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC2803212&req=5

fig2: Inhibition of ethylene action reduces the numbers of SCNs that develop on soybean roots, and addition of ethylene increases the number. (A) Continuous exposure of SCN-inoculated monoxenic roots to no inhibitors (control), 2 μl l−1 1-MCP, 5000 μl l−1 NBD, or 1 μl l−1 ethylene. (B) Exposure of monoxenic roots to 5000 μl l−1 NBD for 10 d intervals preceded or followed by exposure to air with no inhibitor, or continuous exposure of roots to 5000 μl l−1 NBD for 30 d or to 5000 μl l−1 NBD plus 100 μl l−1 ethylene. (C) Continuous exposure of monoxenic roots to 2000 μl l−1 NBD or 2000 μl l−1 NBD plus 25 μl l−1 ethylene.

Mentions: Bent et al. (2006) reported that the number of nematodes on identically inoculated roots was inhibited by 50% in a soybean mutant that was partially resistant to ethylene action. To determine if a more complete block of ethylene action might produce a greater inhibition of SCN numbers, ethylene action was inhibited with 2 μl l−1 1-MCP or 5000 μl l−1 NBD. 1-MCP and NBD reduced nematode numbers on cultured roots by nearly 90% (Fig. 2A). 1-MCP is a non-competitive inhibitor of ethylene action and its effect on ethylene action appears to be irreversible until new receptors are synthesized in the absence of 1-MCP (Sisler, 2006). NBD, on the other hand, is a competitive inhibitor of ethylene and its effect on ethylene action can be reversed by addition of an excessive amount of ethylene (Sisler, 2006). To determine which stage of SCN development was sensitive to ethylene inhibition 5000 μl l−1 NBD was applied for 10 d intervals at 0–10, 10–20, and 20–30 dpi. Treatment of the infected roots with NBD at 10 d intervals reduced the number of mature females counted at 30 dpi by ∼20% at all three stages (Fig. 2B). This is in contrast to the continuous (0–30 dpi) treatment that inhibited SCN numbers by >95% (Fig. 2B). NBD at the high concentration of 5000 μl l−1 was chosen to maximize inhibition of the ethylene response (Sisler et al., 1986); however, NDB inhibition of SCN numbers was only partly reversed by the addition of 100 μl l−1 ethylene. A reduced level of NBD, 2000 μl l−1, was less effective on nematode numbers but the inhibition was fully reversed with 25 μl l−1 ethylene; however, root morphology looked similar between the NBD-treated and non-treated roots (result not shown), indicating that ethylene action was not fully inhibited at 2000 μl l−1. NBD at 5000 μl l−1, as did 2 μl l−1 1-MCP, caused the roots to grow long and thin with less branching and a slightly lower total root mass than the controls.


1-Aminocyclopropane-1-carboxylic acid (ACC) concentration and ACC synthase expression in soybean roots, root tips, and soybean cyst nematode (Heterodera glycines)-infected roots.

Tucker ML, Xue P, Yang R - J. Exp. Bot. (2009)

Inhibition of ethylene action reduces the numbers of SCNs that develop on soybean roots, and addition of ethylene increases the number. (A) Continuous exposure of SCN-inoculated monoxenic roots to no inhibitors (control), 2 μl l−1 1-MCP, 5000 μl l−1 NBD, or 1 μl l−1 ethylene. (B) Exposure of monoxenic roots to 5000 μl l−1 NBD for 10 d intervals preceded or followed by exposure to air with no inhibitor, or continuous exposure of roots to 5000 μl l−1 NBD for 30 d or to 5000 μl l−1 NBD plus 100 μl l−1 ethylene. (C) Continuous exposure of monoxenic roots to 2000 μl l−1 NBD or 2000 μl l−1 NBD plus 25 μl l−1 ethylene.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2803212&req=5

fig2: Inhibition of ethylene action reduces the numbers of SCNs that develop on soybean roots, and addition of ethylene increases the number. (A) Continuous exposure of SCN-inoculated monoxenic roots to no inhibitors (control), 2 μl l−1 1-MCP, 5000 μl l−1 NBD, or 1 μl l−1 ethylene. (B) Exposure of monoxenic roots to 5000 μl l−1 NBD for 10 d intervals preceded or followed by exposure to air with no inhibitor, or continuous exposure of roots to 5000 μl l−1 NBD for 30 d or to 5000 μl l−1 NBD plus 100 μl l−1 ethylene. (C) Continuous exposure of monoxenic roots to 2000 μl l−1 NBD or 2000 μl l−1 NBD plus 25 μl l−1 ethylene.
Mentions: Bent et al. (2006) reported that the number of nematodes on identically inoculated roots was inhibited by 50% in a soybean mutant that was partially resistant to ethylene action. To determine if a more complete block of ethylene action might produce a greater inhibition of SCN numbers, ethylene action was inhibited with 2 μl l−1 1-MCP or 5000 μl l−1 NBD. 1-MCP and NBD reduced nematode numbers on cultured roots by nearly 90% (Fig. 2A). 1-MCP is a non-competitive inhibitor of ethylene action and its effect on ethylene action appears to be irreversible until new receptors are synthesized in the absence of 1-MCP (Sisler, 2006). NBD, on the other hand, is a competitive inhibitor of ethylene and its effect on ethylene action can be reversed by addition of an excessive amount of ethylene (Sisler, 2006). To determine which stage of SCN development was sensitive to ethylene inhibition 5000 μl l−1 NBD was applied for 10 d intervals at 0–10, 10–20, and 20–30 dpi. Treatment of the infected roots with NBD at 10 d intervals reduced the number of mature females counted at 30 dpi by ∼20% at all three stages (Fig. 2B). This is in contrast to the continuous (0–30 dpi) treatment that inhibited SCN numbers by >95% (Fig. 2B). NBD at the high concentration of 5000 μl l−1 was chosen to maximize inhibition of the ethylene response (Sisler et al., 1986); however, NDB inhibition of SCN numbers was only partly reversed by the addition of 100 μl l−1 ethylene. A reduced level of NBD, 2000 μl l−1, was less effective on nematode numbers but the inhibition was fully reversed with 25 μl l−1 ethylene; however, root morphology looked similar between the NBD-treated and non-treated roots (result not shown), indicating that ethylene action was not fully inhibited at 2000 μl l−1. NBD at 5000 μl l−1, as did 2 μl l−1 1-MCP, caused the roots to grow long and thin with less branching and a slightly lower total root mass than the controls.

Bottom Line: In addition, an ACS-like sequence was found in the public SCN nucleotide database.Acquisition of a full-length sequence for this mRNA (accession GQ389647) and alignment with transcripts for other well-characterized ACS proteins indicated that the nematode sequence is missing a key element required for ACS activity and therefore probably is not a functional ACS.Moreover, no significant amount of ACC was found in any growth stage of SCN that was tested.

View Article: PubMed Central - PubMed

Affiliation: Soybean Genomics and Improvement Lab, Agricultural Research Service, United States Department of Agriculture, 10300 Baltimore Ave., Beltsville, MD, USA. mark.tucker@ars.usda.gov

ABSTRACT
Colonization of plant roots by root knot and cyst nematodes requires a functional ethylene response pathway. However, ethylene plays many roles in root development and whether its role in nematode colonization is direct or indirect, for example lateral root initiation or root hair growth, is not known. The temporal requirement for ethylene and localized synthesis of ethylene during the life span of soybean cyst nematode (SCN) on soybean roots was further investigated. Although a significant increase in ethylene evolution was not detected from SCN-colonized roots, the concentration of the immediate precursor to ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC), was higher in SCN-colonized root pieces and root tips than in other parts of the root. Moreover, expression analysis of 17 ACC synthase (ACS) genes indicated that a select set of ACS genes is expressed in SCN-colonized root pieces that is clearly different from the set of genes expressed in non-colonized roots or root tips. Semi-quantitative real-time PCR indicated that ACS transcript accumulation correlates with the high concentration of ACC in root tips. In addition, an ACS-like sequence was found in the public SCN nucleotide database. Acquisition of a full-length sequence for this mRNA (accession GQ389647) and alignment with transcripts for other well-characterized ACS proteins indicated that the nematode sequence is missing a key element required for ACS activity and therefore probably is not a functional ACS. Moreover, no significant amount of ACC was found in any growth stage of SCN that was tested.

Show MeSH
Related in: MedlinePlus