Genetic, biochemical, and metabolomic analysis of plant purine catabolism

为了提高作物氮素利用效率，需要深入了解植物氮素再动员。最佳利用氮资源的作物需要较少的施肥，从而降低成本和对环境的有害影响。嘌呤核苷酸降解有助于植物氮的再动员，但这一途径的几种酶尚未被遗传鉴定。我们建议(i)鉴定和表征拟南芥和大豆中嘌呤降解“缺失”的酶，（ii）利用一系列突变体、瞬时敲除植物和过表达系研究拟南芥和大豆中嘌呤降解改变的生理和代谢影响。将测量生长、氮再动员和代谢物谱。嘌呤分解代谢在转录和转录后水平上的调控取决于不同的生理条件。嘌呤降解中间体的积累可能具有毒性作用（在尿酸盐的情况下）或对植物有益（在尿囊素的情况下），然后在某些应激情况下成为所需的代谢输出。以尿囊素含量改变的拟南芥为研究对象，探讨该化合物在衰老、盐胁迫和渗透胁迫中的生理作用。拟南芥尿酸酶突变体将用于研究植物细胞和分子水平上的尿酸毒性。这些研究可能也会让人们对尿酸盐对人类的毒性有新的认识，从而导致痛风和莱希尼汉综合征等疾病。

A profound understanding of plant nitrogen (N) remobilisation is needed to improve crop nitrogen use efficiency. Crops that make optimal use of their N resources require less fertilisation which reduces costs and hazardous effects to the environment. Purine nucleotide degradation contributes to N remobilisation in plants but several enzymes of this pathway have not been identified genetically yet. We propose to (i) identify and characterise “missing” enzymes in purine degradation in arabidopsis and soybean, (ii) investigate the physiological and metabolic effects of altered purine degradation in arabidopsis and soybean using a range of mutants, transient knock-down plants, and over-expression lines. Growth, N remobilisation, and metabolite profiles will be measured. The regulation of purine catabolism on transcriptional and post-transcriptional level will be determined in different physiological situations. Accumulation of purine degradation intermediates can have toxic effects (in the case of urate) or be beneficial to the plant (in case of allantoin) and then be a desired metabolic output in certain stress situations. Using arabidopsis plants altered in allantoin content we will investigate the physiological role of this compound in senescence, salt and osmotic stress. A uricase mutant of arabidopsis will be employed to investigate urate toxicity on cellular and molecular level in plants. Potentially these studies will also permit new insights into urate toxicity in humans leading to diseases like gout and Lesch Nyhan syndrome.