Journal Article

Phenylalanine ammonia lyase functions as a switch directly controlling the accumulation of calycosin and calycosin-7-<i>O</i>-β-<span class="smallCaps">D</span>-glucoside in <i>Astragalus membranaceus</i> var. <i>mongholicus</i> plants

Haiyun Pan, Yuguo Wang, Yongfeng Zhang, Tongshui Zhou, Changming Fang, Peng Nan, Xiaoqiang Wang, Xiaobing Li, Yinlong Wei and Jiakuan Chen

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 59, issue 11, pages 3027-3037
Published in print August 2008 | ISSN: 0022-0957
Published online June 2008 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jxb/ern152
Phenylalanine ammonia lyase functions as a switch directly controlling the accumulation of calycosin and calycosin-7-O-β-D-glucoside in Astragalus membranaceus var. mongholicus plants

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Previously it had been shown that calycosin and calycosin-7-O-β-D-glucoside (CGs) accumulate in whole plants, mainly in leaves, of Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao (A. mongholicus) plants in response to low temperature. In this work, it was demonstrated that the influences of different conditions on CGs biosynthesis, by examining the changes in CGs content, as well as the expression of related genes, including phenylalanine ammonia lyase (PAL1), cinnamic acid 4-hydroxylase (C4H), chalcone synthase (CHS), chalcone reductase (CHR), chalcone isomerase (CHI), isoflavone synthase (IFS), and isoflavone 3′-hydroxylase (I3′H). The seven gene mRNAs accumulated in leaves of A. mongholicus upon exposure to low temperature in a light-dependent manner, though they exhibited different expression patterns. Transcriptions of CHS, CHR, CHI, IFS, and I3′H of the calycosin-7-O-β-D-glucoside pathway were all up-regulated when plants were transferred from 16 °C to 2 °C or 25 °C or from 2 °C (kept for 24 h) to 25 °C. However, fluctuations in temperature influenced differently the transcriptions of PAL1 and C4H of the general phenylpropanoid pathway in leaves. Moreover, the amount of PAL1 expression changed sharply up and down, consistent with the variation of the content of CGs. PAL enzyme activity appears to be the limiting factor in determining the CGs levels. The inhibitor of PAL enzyme, L-α-aminooxy-β-phenylpropionic acid, almost entirely shut down CGs accumulation at low temperature. All these results confirmed that PAL1, as a smart gene switch, directly controls the accumulation of CGs in A. mongholicus plants, in a light-dependent manner, during low temperature treatment.

Keywords: Accumulation; enzyme inhibitor; gene switch; isoflavonoid; phenylalanine ammonia lyase

Journal Article.  6006 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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