Department of Molecular Genetics, Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Campus UAB, Bellaterra (Cerdanyola del Vallès), Barcelona, Spain.
BMC Plant Biol. 2013 Aug 5;13:109. doi: 10.1186/1471-2229-13-109.
Polyamines (PAs) are oxidatively deaminated at their primary or secondary amino-groups by copper-containing amine oxidases (CuAOs) or FAD-dependent amine oxidases (PAOs), respectively. Both enzymes have long been considered to be apoplastic proteins. However, three out of five PAO isoforms in Arabidopsis thaliana are localized in peroxisomes, while the other two PAOs are predicted to be cytosolic. Interestingly, most of these PAOs do not contribute to terminal PA oxidation, but instead are involved in the back-conversion pathway, producing spermidine from spermine and putrescine from spermidine, which in turn is inhibited by putrescine. This opens the question as to whether PAs are catabolized in the apoplast of Arabidopsis and if the terminal oxidation occurs in the peroxisomes. The main objective of this study was to know if these catabolic processes are mediated by CuAOs.
A. thaliana contains ten genes annotated as CuAOs, but only one (ATAO1) has been characterized at the protein level. Reported herein is the characterization of three genes encoding putative Arabidopsis CuAOs (AtCuAO1, AtCuAO2 and AtCuAO3). These genes encode functional CuAOs that use putrescine and spermidine as substrates. AtCuAO1, like ATAO1, is an extracellular protein, while AtCuAO2 and AtCuAO3 are localized in peroxisomes. The three genes present a different expression profile in response to exogenous treatments, such as application of abcisic acid, methyl jasmonate, salycilic acid, flagellin 22 and wounding.
PA catabolism in the Arabidopsis apoplast is mediated predominantly by CuAOs, while in peroxisomes the co-localization of CuAO-dependent terminal catabolism with PAO-back-conversion machineries might contribute to modulating putrescine-mediated inhibition of the back-conversion, suggesting the occurrence of a tight coordination between both catabolic pathways. The expression profile of AtCuAO1-3 in response to different exogenous treatments, together with the different localization of the corresponding proteins, provides evidence for the functional diversification of Arabidopsis CuAO proteins.
多胺（PAs）在其一级或二级氨基基团处被含铜胺氧化酶（CuAOs）或 FAD 依赖性胺氧化酶（PAOs）氧化脱氨基，分别。这两种酶长期以来一直被认为是质外体蛋白。然而，拟南芥中的 5 种 PAO 同工酶中有 3 种定位于过氧化物酶体中，而另外 2 种 PAO 被预测为细胞质。有趣的是，这些 PAO 中的大多数不参与末端 PA 氧化，而是参与反向转化途径，从腐胺中产生 spermidine，从 spermidine 中产生 putrescine，而 putrescine 又被 putrescine 抑制。这就提出了一个问题，即在拟南芥的质外体中是否代谢多胺，以及末端氧化是否发生在过氧化物酶体中。本研究的主要目的是了解这些代谢过程是否由 CuAOs 介导。
拟南芥含有 10 个被注释为 CuAOs 的基因，但只有一个（ATAO1）在蛋白质水平上得到了表征。本文报道了 3 个编码拟南芥 CuAOs（AtCuAO1、AtCuAO2 和 AtCuAO3）的基因的特征。这些基因编码功能性的 CuAOs，可将腐胺和 spermidine 作为底物。AtCuAO1 与 ATAO1 一样，是一种细胞外蛋白，而 AtCuAO2 和 AtCuAO3 则定位于过氧化物酶体中。这三个基因对外源处理表现出不同的表达谱，如应用脱落酸、茉莉酸甲酯、水杨酸、鞭毛蛋白 22 和创伤。
拟南芥质外体中的 PA 代谢主要由 CuAOs 介导，而过氧化物酶体中 CuAO 依赖性末端代谢与 PAO-反向转化机制的共定位可能有助于调节 putrescine 介导的反向转化抑制，表明这两种代谢途径之间存在紧密的协调。AtCuAO1-3 对不同外源处理的表达谱，以及相应蛋白的不同定位，为拟南芥 CuAO 蛋白的功能多样化提供了证据。
