Efetova Marina, Zeier Jürgen, Riederer Markus, Lee Chil-Woo, Stingl Nadja, Mueller Martin, Hartung Wolfram, Hedrich Rainer, Deeken Rosalia
Department of Molecular Plant Physiology and Biophysics , Biocenter, Julius-von-Sachs-Institute, University of Wuerzburg, D-97082 Wuerzburg, Germany.
Plant Physiol. 2007 Nov;145(3):853-62. doi: 10.1104/pp.107.104851. Epub 2007 Sep 7.
Crown gall tumors induced by Agrobacterium tumefaciens represent a sink that has to be provided with nutrients and water by the host plant. The lack of an intact epidermis or cuticle results in uncontrolled loss of water. However, neither the tumor nor the host plant displays wilting. This phenomenon points to drought adaptation in both tumors and the crown gall host plant. To understand the underlying molecular mechanisms of protection against desiccation the gene expression pattern of Arabidopsis (Arabidopsis thaliana) tumors was integrated with the profile of stress metabolites: Arabidopsis tumors accumulated high amounts of abscisic acid (ABA), the ethylene precursor aminocyclopropyl carboxylic acid, osmoprotectants, and form a suberized periderm-like protective layer. Suberization of the outer tumor cell layers most likely is mediated by ABA since external application of ABA induced suberization of Arabidopsis roots. However, the expression level of the classical marker genes, known to respond to drought stress and/or ABA, was lower in tumors. Instead another set of drought and/or ABA-inducible genes was more highly transcribed. Elevated transcription of several ABA-dependent aquaporin genes might indicate that ABA controls the water balance of the tumor. The retarded tumor growth on abi and aba mutant plants underlined the importance of a tumor-specific ABA signaling pathway. Taken together, we propose that ABA is an important signal for protection of tumors against desiccation and thus supports tumor development.
根癌农杆菌诱导产生的冠瘿瘤是一个汇，必须由寄主植物为其提供养分和水分。缺乏完整的表皮或角质层会导致水分无节制地流失。然而，无论是肿瘤还是寄主植物都没有出现萎蔫现象。这种现象表明肿瘤和冠瘿寄主植物都具有干旱适应性。为了了解抵御干燥的潜在分子机制，将拟南芥肿瘤的基因表达模式与胁迫代谢物谱整合起来：拟南芥肿瘤积累了大量脱落酸（ABA）、乙烯前体氨基环丙烷羧酸、渗透保护剂，并形成了一层类似栓质化周皮的保护层。肿瘤外层细胞的栓质化很可能是由ABA介导的，因为外源施加ABA会诱导拟南芥根的栓质化。然而，已知对干旱胁迫和/或ABA有响应的经典标记基因在肿瘤中的表达水平较低。相反，另一组干旱和/或ABA诱导型基因转录水平更高。几个ABA依赖的水通道蛋白基因转录水平升高可能表明ABA控制着肿瘤的水分平衡。abi和aba突变体植物上肿瘤生长受阻突出了肿瘤特异性ABA信号通路的重要性。综上所述，我们认为ABA是保护肿瘤免受干燥影响的重要信号，从而支持肿瘤的发育。
