The Key Lab of Plant Cell Engineering and Germplasm Innovation, Ministry of Education of China, School of Life Sciences, Shandong University, Jinan, Shandong, PR China.
School of Pharmacy, Liaocheng University, Liaocheng, Shandong, China.
Ann Bot. 2018 Dec 31;122(7):1203-1217. doi: 10.1093/aob/mcy123.
Nowadays, the plant family 1 glycosyltransferases (UGTs) are attracting more and more attention since members of this family can improve the properties of secondary metabolites and have significantly enriched the chemical species in plants. Over the past decade, most studies on UGTs have been conducted in Arabidopsis thaliana and they were proved to play diverse roles during the plant life cycle. The Zea mays (maize) GT1 family comprises a large number of UDP-glycosyltransferase (UGT) members. However, their enzyme activities and the biological functions are rarely revealed. In this study, a maize flavonol glycosyltransferase, UFGT2, is identified and its biological role is characterized in detail.
The UFGT2 enzyme activity, the flavonol and glycoside levels in planta were examined by high- performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). The functions of UFGT2 in modifying flavonols, mediating flavonol accumulation and improving stress tolerance were analysed using two ufgt2 mutants and transgenic arabidopsis plants.
By in vitro enzyme assay, the maize UFGT2 was found to show strong activity towards two flavonols: kaemferol and quercetin. Two ufgt2 knockout mutants, Mu689 and Mu943, exhibited obvious sensitivity to salt and drought stresses. The endogenous quercetin and kaempferol glycosides, as well as the total flavonol levels were found to be substantially decreased in the two ufgt2 mutants, with declined H2O2-scavenging capacity. In contrast, ectopic expression of UFGT2 in arabidopsis led to increased flavonol contents and enhanced oxidative tolerance. Moreover, expression of typical stress-related genes in arabidopsis and maize were affected in UFGT2 overexpression plants or knockout mutants in response to abiotic stresses. UFGT2 was also transferred into the arabidopsis ugt78d2 mutant and it was found to recover the deficient flavonol glycoside pattern in the ugt78d2 mutant, which confirmed its catalysing activity in planta.
It is demonstrated in our study that a maize glycosyltransferase, UFGT2, involved in modifying flavonols, contributes to improving plant tolerance to abiotic stresses.
如今，植物家族 1 糖基转移酶（UGTs）越来越受到关注，因为该家族的成员可以改善次生代谢物的性质，并显著丰富植物中的化学物质种类。在过去的十年中，对 UGTs 的大多数研究都在拟南芥中进行，证明它们在植物生命周期中发挥着多样化的作用。玉米 GT1 家族包含大量的 UDP-糖基转移酶（UGT）成员。然而，它们的酶活性和生物学功能很少被揭示。本研究鉴定了一个玉米类黄酮糖基转移酶 UFGT2，并详细描述了其生物学功能。
通过高效液相色谱（HPLC）和液相色谱-质谱联用（LC-MS）检测 UFGT2 酶活性、植物内类黄酮和糖苷水平。利用两个 ufgt2 突变体和转基因拟南芥植物分析 UFGT2 在修饰类黄酮、介导类黄酮积累和提高胁迫耐受性方面的功能。
通过体外酶活性测定，发现玉米 UFGT2 对两种类黄酮：山奈酚和槲皮素具有很强的活性。两个 ufgt2 敲除突变体 Mu689 和 Mu943 对盐和干旱胁迫表现出明显的敏感性。两个 ufgt2 突变体的内源槲皮素和山奈酚糖苷以及总类黄酮水平显著降低，H2O2 清除能力下降。相比之下，UFGT2 在拟南芥中的异位表达导致类黄酮含量增加和氧化胁迫耐受性增强。此外，在拟南芥和玉米中，胁迫相关基因的表达在 UFGT2 过表达植物或敲除突变体中受到影响，以响应非生物胁迫。UFGT2 还被转移到拟南芥 ugt78d2 突变体中，发现它能够恢复 ugt78d2 突变体中缺乏的类黄酮糖苷模式，这证实了它在植物体内的催化活性。
本研究表明，玉米糖基转移酶 UFGT2 参与修饰类黄酮，有助于提高植物对非生物胁迫的耐受性。
