Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA Department of Genetics, University of Georgia, Athens, GA 30602, USA.
Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA.
J Exp Bot. 2014 Aug;65(15):4191-200. doi: 10.1093/jxb/eru192. Epub 2014 May 6.
The diversity of phenylpropanoids offers a rich inventory of bioactive chemicals that can be exploited for plant improvement and human health. Recent evidence suggests that glycosylation may play a role in the partitioning of phenylpropanoid precursors for a variety of downstream uses. This work reports the functional characterization of a stress-responsive glycosyltransferase, GT1-316 in Populus. GT1-316 belongs to the UGT84A subfamily of plant glycosyltransferase family 1 and is designated UGT84A17. Recombinant protein analysis showed that UGT84A17 is a hydroxycinnamate glycosyltransferase and able to accept a range of unsubstituted and substituted cinnamic and benzoic acids as substrates in vitro. Overexpression of GT1-316 in transgenic Populus led to plant-wide increases of hydroxycinnamoyl-glucose esters, which were further elevated under N-limiting conditions. Levels of the two most abundant flavonoid glycosides, rutin and kaempferol-3-O-rutinoside, decreased, while levels of other less abundant flavonoid and phenylpropanoid conjugates increased in leaves of the GT1-316-overexpressing plants. Transcript levels of representative phenylpropanoid pathway genes were unchanged in transgenic plants, supporting a glycosylation-mediated redirection of phenylpropanoid carbon flow as opposed to enhanced phenylpropanoid pathway flux. The metabolic response of N-replete transgenic plants overlapped with that of N-stressed wild types, as the majority of phenylpropanoid derivatives significantly affected by GT1-316 overexpression were also significantly changed by N stress in the wild types. These results suggest that UGT84A17 plays an important role in phenylpropanoid metabolism by modulating biosynthesis of hydroxycinnamoyl-glucose esters and their derivatives in response to developmental and environmental cues.
苯丙烷类的多样性提供了丰富的生物活性化学物质库存，可用于植物改良和人类健康。最近的证据表明，糖基化可能在苯丙烷前体的分配中发挥作用，以用于各种下游用途。本研究报告了杨树中应激响应糖基转移酶 GT1-316 的功能特征。GT1-316 属于植物糖基转移酶家族 1 的 UGT84A 亚家族，被指定为 UGT84A17。重组蛋白分析表明，UGT84A17 是一种羟基肉桂酰基糖基转移酶，能够在体外接受一系列未取代和取代的肉桂酸和苯甲酸作为底物。GT1-316 在转基因杨树中的过表达导致植物中羟基肉桂酰基-葡萄糖酯的广泛增加，在氮限制条件下进一步升高。两种最丰富的类黄酮糖苷芦丁和山奈酚-3-O-芦丁糖苷的水平降低，而 GT1-316 过表达植物叶片中其他较少的类黄酮和苯丙烷轭合物的水平升高。转基因植物中代表性的苯丙烷途径基因的转录水平没有变化，支持糖基化介导的苯丙烷碳流重定向，而不是增强苯丙烷途径通量。氮充足的转基因植物的代谢反应与氮胁迫的野生型重叠，因为 GT1-316 过表达显著影响的大多数苯丙烷衍生物在野生型中也因氮胁迫而显著变化。这些结果表明，UGT84A17 通过调节羟基肉桂酰基-葡萄糖酯及其衍生物的生物合成，在响应发育和环境线索时，在苯丙烷代谢中发挥重要作用。
