Strategies for enhancement of bioactive flavonol glycosides in plants

黄酮醇（例如槲皮素）是众所周知的植物化学物质。将它们纳入人类饮食中可以防止与包括阿尔茨海默氏症在内的慢性疾病相关的破坏性自由基的积累。大约5%的65岁以上的加拿大人被诊断患有某种形式的痴呆症。黄酮醇提供了一种预防措施，以抵消加拿大每年用于治疗这些疾病的330亿美元。在人类饮食中，黄酮醇不像它们的糖苷那样可用，糖苷形式倾向于在植物（例如洋葱，羽衣甘蓝，花椰菜）和水果（例如苹果，葡萄，辣椒，番茄）组织中占主导地位。在植物中，黄酮醇作为一种或多种糖的缀合物存在，包括单糖苷、二糖苷和双糖苷（例如槲皮素3-O-β-葡糖苷-7-O-α-鼠李糖苷）。这些化合物在植物中的生理作用尚不清楚，但有证据表明它们与生长，环境胁迫和植物-昆虫相互作用有关。植物黄酮醇双糖苷的积累是对环境扰动的响应，包括UV-B光、寒冷、营养缺乏，并且依赖于生物合成途径的转录调节。植物（包括食品）中黄酮醇的保存不仅取决于生物合成过程，因为每天损失约1-35%是典型的，包括在收获后处理期间。黄酮醇双糖苷的水平可以通过最大限度地减少其在植物中的降解来实现，这一过程知之甚少。 在过去的6年里，我的实验室已经建立了植物中黄酮醇双糖苷及其相关分子损失的生化证据。我们目前的研究重点是在拟南芥，由于遗传突变体的可用性，黄酮醇生物化学的模式植物，这种catenorase的特征。我们研究的一个亮点包括鉴定酶组分，特别是β-葡萄糖苷酶，作为这些生物活性化合物损失的可能的第一步。我们对阐明植物中完整的黄酮醇双糖苷催化途径很感兴趣。我们的实验室使用尖端的分析化学平台以及生理学，经典生物化学和生物技术来识别与这些重要小分子的周转相关的基因/酶。除了为生物化学，分子生物学和分析化学的学生提供独特的培训机会外，本研究旨在提高植物黄酮醇催化剂的知识。此外，这项新的研究提供了潜在的工具，基因工程和分子育种策略，目标黄酮醇生物强化在经济上重要的作物植物。

Flavonols (e.g. quercetin) are well known phytochemicals. Their incorporation in the human diet may prevent accumulation of damaging radicals associated with chronic diseases including Alzheimer’s. Approximately 5% of Canadians over the age of 65 are diagnosed with some form of dementia. Flavonols offer a preventative measure to offset the $33 billion spent annually to treat these disorders in Canada. In the human diet, flavonols are not as available as their glycosides, forms which tend to predominate across vegetative (e.g. onion, kale, broccoli) and fruit (e.g. apple, grape, pepper, tomato) tissues. In plants, flavonols exists as conjugates of one or more sugars, including monoglycosides, diglycosides and bisglycosides (e.g. quercetin 3-O-ß-glucoside-7-O-a-rhamnoside). The physiological roles of these compounds in plants are not yet clear, but evidence suggests they are linked to growth, environmental stress, and plant-insect interactions. Plant accumulation of flavonol bisglycosides occurs in response to environmental perturbations, including UV-B light, chilling, nutrient deficiencies, and is dependent upon transcriptional regulation of the biosynthetic pathway. Flavonol preservation in plants, including foodstuffs, is not solely dependent upon biosynthetic processes as losses on the order of 1-35% per day are typical, including during postharvest handling. Enhanced levels of flavonol bisglycosides may be achieved by minimizing their degradation in planta, processes that are little understood. Over the past 6 years, my laboratory has established the biochemical evidence for the loss of flavonol bisglycosides and their related molecules from plants. Our current research focuses on characterizing this catabolism in Arabidopsis thaliana, a model plant for flavonol biochemistry due to the availability of genetic mutants. A highlight of our research includes the identification of an enzymatic component, specifically a ß-glucosidase, as a possible first step in the loss of these bioactive compounds. We are interested in elucidation of the complete flavonol bisglycoside catabolism pathway in plants. Our laboratory uses cutting edge analytical chemistry platforms together with physiology, classical biochemistry and biotechnology to identify the genes/enzymes associated with the turnover of these important small molecules. In addition to providing unique training opportunities for students in biochemistry, molecular biology and analytical chemistry, this research aims to enhance knowledge of plant flavonol catabolism. Moreover, this novel research provides potential tools for genetic engineering and molecular breeding strategies targeting flavonol biofortification in economically important crop plants.