Control of cellular damage: dissecting the physiological functions of the glyoxalase system in plants

活性羰基物种(RCS)是细胞代谢过程中形成的具有高活性、亲电性的单、双羰基小分子。在人类中，RCs参与了几种退化过程和疾病。在植物中，最丰富的RCs是乙二醛(GO)和甲基乙二醛(MGO)，它们的形成与糖酵解和Calvin-Benson循环的通量密切相关。RCS在暴露于各种非生物胁迫时在植物组织中积累，如盐分、干旱和寒冷。这种联系促使人们加紧研究通过RCS清除系统来提高植物适合度和产量的策略。GO和MGO解毒的主要途径是乙醛酶系统，该系统由S-D-乳糖基谷胱甘肽裂解酶(GLXI)和S-2-羟基酰基谷胱甘肽水解酶(GLXII)两种酶依次作用。植物也有类似GLXi的蛋白，它们与GLXi蛋白一起属于邻近的氧络合物超家族。我们以前的工作表明：(I)一组特定的GLXi蛋白是病毒所特有的，可能与一组病毒特异性的GLXII蛋白共同进化；(Ii)拟南芥GLXi亚型似乎以不同的特异性在体内作用于不同的RCS。在这项建议中，我们旨在阐明不同的GLXi和GLXII活性参与不同RCs对细胞损伤的控制。为了实现这一目标，我们建议采用互补的方法，包括(I)修改特定GLXi和GLXII亚型表达的植物品系的功能特征；(Ii)重组GLXi的生化特征；(Iii)使用非靶向代谢组学来寻找GLXi亚型的额外底物；以及(Iv)使用互补的蛋白质-蛋白质相互作用方法来分析GLXi和GLXII亚型是否物理上相互作用以有效地引导反应的中间产物。

Reactive carbonyl species (RCS) are highly reactive small electrophilic mono- and di-carbonyl molecules formed during cellular metabolism. In humans, RCS are involved in several degenerative processes and diseases. In plants, the most abundant RCS are glyoxal (GO) and methylglyoxal (MGO), whose formation is closely connected to the fluxes through glycolysis and the Calvin-Benson cycle. RCS accumulate in plant tissues upon exposure to various abiotic stresses such as salinity, drought, and cold. This connection has prompted intense research on strategies for the enhancement of plant fitness and yield through RCS scavenging systems. The main pathway to detoxify GO and MGO is the glyoxalase (GLX) system, which consists of two enzymes, S-D-lactoylglutathione lyase (glyoxalase I, GLXI) and S-2-hydroxyacylglutathione hydrolase (glyoxalase II, GLXII), acting in sequence. Plants possess also GLXI-like proteins, which, together with the GLXI proteins, belong to the vicinal oxygen chelate superfamily. Our previous work suggests that (i) a specific group of GLXI proteins are unique to the Viridiplantae and likely co-evolved with a cluster of Viridiplantae-specific GLXII proteins; and (ii) Arabidopsis GLXI isoforms seem to act in vivo on different RCS with different specificity. In this proposal, we aim to clarify the participation of different GLXI and GLXII activities in the control of cellular damage by different RCS. To achieve this aim, we propose to follow complementary approaches, including (i) the functional characterization of plant lines with modified expression of specific GLXI and GLXII isoforms; (ii) the biochemical characterization of recombinant GLXI; (iii) the use of untargeted metabolomics to pursue the identification of additional substrates of the GLXI isoforms; and (iv) to use complementary protein-protein interaction approaches to analyse if GLXI and GLXII isoforms physically interact to efficiently channel the intermediates of the reactions.