Metabolism of salicylic acid in wild-type, ugt74f1 and ugt74f2 glucosyltransferase mutants of Arabidopsis thaliana
作者:John V. Dean、Sean P. Delaney
DOI:10.1111/j.1399-3054.2007.01041.x
日期:2008.4
Arabidopsis thaliana contains two salicylic acid (SA) glucosyltransferase enzymes designated UGT74F1 and UGT74F2. UGT74F1 forms only SA 2‐O‐β‐D‐glucose (SAG), while UGT74F2 forms both SAG and the SA glucose ester (SGE). In an attempt to determine the in vivo role of each SA glucosyltransferase (SAGT), the metabolism of SA in ugt74f1 and ugt74f2 mutants was examined and compared with that of the wild‐type. The three major metabolites formed in wild‐type Arabidopsis included SAG, SGE, and 2,5‐dihydroxbenzoic acid 2‐O‐β‐D‐glucose (DHB2G). This is the first description of DHB2G as a major metabolite of SA in plants. The major metabolites of SA formed in ugt74f1 mutants were SGE, SAG and 2,5‐dihydroxybenzoic acid 5‐O‐β‐D‐glucose (DHB5G). DHB5G was not formed in the wild‐type plants. SAG and DHB2G were the main metabolites of SA in ugt74f2 mutants. The ugt74f2 mutant was unable to form SGE. Only SGE could be detected during in vitro SAGT assays of untreated wild‐type and ugt74f1 mutants. This activity was because of constitutive UGT74F2 activity. Both SGE and SAG could be formed during in vitro assays of SA‐pretreated wild‐type and ugt74f1 leaves. Neither SAG nor SGE could be detected during the in vitro SAGT assays of untreated ugt74f2 leaves. Only SAG was formed during the in vitro SAGT assays of SA‐pretreated ugt74f2 leaves. The SAG formation was a result of the UGT74F1 activity. This work demonstrates that changes in the activity of either SAGT enzyme can have a dramatic effect on the metabolism of exogenously supplied SA in Arabidopsis.
Arabidopsis thaliana 中包含两种水杨酸(SA)葡萄糖基转移酶(SAGT),分别命名为UGT74F1和UGT74F2。UGT74F1仅形成SA 2-O-β-D-葡萄糖(SAG),而UGT74F2可以形成SAG和SA葡萄糖酯(SGE)。为了确定每种SA葡萄糖基转移酶在体内的功能,研究者比较了ugt74f1 和ugt74f2 突变体与野生型植物中SA的代谢情况。
在野生型Arabidopsis 中,三种主要的代谢产物包括SAG、SGE和2,5-二羟基苯甲酸2-O-β-D-葡萄糖(DHB2G)。这是首次将DHB2G描述为植物中SA的主要代谢产物。在ugt74f1 突变体中,SA的主要代谢产物为SGE、SAG和2,5-二羟基苯甲酸5-O-β-D-葡萄糖(DHB5G)。DHB5G在野生型植物中并未形成。而在ugt74f2 突变体中,SAG和DHB2G是SA的主要代谢产物,且该突变体无法形成SGE。
在体外SAGT活性测定中,未处理的野生型和ugt74f1 突变体只能检测到SGE的形成,这一活性归因于UGT74F2的组成型活性。然而,在SA预处理的野生型和ugt74f1 叶片中,既能形成SGE也能形成SAG。在未经处理的ugt74f2 叶片中,无论是SGE还是SAG均未被检测到。然而,在SA预处理的ugt74f2 叶片中,只形成了SAG,这是由于UGT74F1的活性。
这项研究展示了两种SAGT酶活性的变化对拟南芥中外源供给的SA代谢产生的显著影响。