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Title: 1-aminocyclopropane-1-carboxylic acid (ACC) concentration and ACC synthase expression in soybean roots and root tips and soybean cyst nematode (Heterodera glycines) colonized root pieces

Author
item Tucker, Mark
item PING, XUE - JOHNS HOPKINS UNIVERSITY
item Yang, Ronghui

Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2009
Publication Date: 1/10/2010
Citation: Tucker, M.L., Ping, X., Yang, R. 2010. 1-aminocyclopropane-1-carboxylic acid (ACC) concentration and ACC synthase expression in soybean roots and root tips and soybean cyst nematode (Heterodera glycines) colonized root pieces. Journal of Experimental Botany. 61(2):463-472.

Interpretive Summary: Soybean cyst nematode (SCN) is the most economically damaging pathogen of soybean. It has been estimated that damage to the United States soybean crop by SCN costs farmers one billion dollars annually. It is fairly well established that the plant hormone ethylene is important to high numbers of nematode infections on plant roots. The evidence for this conclusion stems mostly from research where ethylene synthesis or action was inhibited. However, ethylene is necessary for normal root growth. Abnormal root development may be why nematode infections are less when ethylene synthesis or action is disturbed. To better understand the role of ethylene in SCN infection of soybean roots we examined how ethylene synthesis genes and chemical precursors to ethylene changed during an SCN infection. Clearly, ethylene synthesis substrates and gene expression were different in SCN infected roots compared to non-infected roots. A better understanding of how these genes and chemical substrates are altered by the nematode will greatly improve the ability of scientists and industrial partners to control SCN infection of soybean.

Technical Abstract: It's fairly well established that a functional ethylene response path is important to root knot and cyst nematode colonization of plant roots. However, ethylene plays many roles in root development and the role of ethylene in nematode colonization of roots may be indirect, e.g. lateral root initiation or root hair growth. We confirmed the need for ethylene in soybean cyst nematode (SCN) colonization of soybean roots and extended our understanding of its role by measuring the concentration of the immediate precursor to ethylene, 1-aminocyclopropane-l-carboxylic acid (ACC), and the expression patterns for 17 ACC synthase (ACS) genes in root tips and SCN colonized and non-colonized root pieces. ACC concentration is higher in SCN colonized root pieces and root tips than other parts of the root. Moreover, ACS gene expression is clearly different in SCN colonized root pieces compared to non-colonize roots or root tips. Semi-quantitative RT-PCR indicates that ACS transcript accumulation correlates with the increased concentration of ACC in root tips and SCN colonized root pieces. In addition, an ACS-like cDNA was discovered in SCN (accession GQ389647). A full-length sequence for this mRNA indicated that it probably isn't a functional ACS and no significant amount of ACC was found in any growth stage of SCN.