Arginase-negative mutants of Arabidopsis exhibit increased nitric oxide signaling in root development
Arginase-negative mutants of Arabidopsis exhibit increased nitric oxide signaling in root development
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DOI：
10.1104/pp.108.121459
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发表时间：
2008-08-01
期刊：
影响因子：
7.4
通讯作者：
Polacco, Joe C.
中科院分区：
文献类型：
--
作者：
Flores, Teresita;Todd, Christopher D.;Polacco, Joe C.
精氨酸酶结构基因（分别编码精氨酸 [Arg] 酰胺水解酶-1 和 -2 的 ARGAH1 或 ARGAH2）的突变导致拟南芥 (Arabidopsis thaliana) 幼苗中侧根和不定根的形成增加，并增加一氧化氮 (NO) 积累和流出，通过荧光捕获 3-amino, 4-aminomethyl- 2', 分别为 7'-二氟荧光素二乙酸酯和二氨基罗丹明-4M。幼苗暴露于合成生长素萘乙酸后，与野生型相比，argah1-1 和 argah2-1 中 NO 的积累有差异性增强。在所有基因型中，许多3-氨基，4-氨基甲基-2'，7'-二氟荧光素二乙酸酯荧光源自线粒体。精氨酸酶均定位于线粒体基质并且密切相关。然而，它们的表达水平和模式不同：ARGAH1 编码次要活性，ARGAH1 驱动的 β-葡萄糖醛酸酶 (GUS) 在整个幼苗中表达； ARGAH2::GUS 表达模式更加本地化。萘乙酸使突变体的幼苗侧根数量（每个主根的侧根总数）增加到野生型的两倍，这与内部NO增加导致根部生长素信号增强的情况一致。一致地，argah1-1 和 argah2-1 显示生长素响应报告基因 DR5:::GUS 在根尖、新生侧根和下胚轴中的表达增加。我们认为精氨酸或精氨酸衍生物是潜在的一氧化氮来源，突变体中精氨酸酶活性的降低导致精氨酸更多地转化为一氧化氮，从而增强根中的生长素作用。与野生型相比，补充 Arg 诱导不定根以及 argah1-1 和 argah2-1 中 NO 积累增加支持了该模型。
Mutation of either arginase structural gene (ARGAH1 or ARGAH2 encoding arginine [Arg] amidohydrolase-1 and -2, respectively) resulted in increased formation of lateral and adventitious roots in Arabidopsis ( Arabidopsis thaliana) seedlings and increased nitric oxide ( NO) accumulation and efflux, detected by the fluorogenic traps 3-amino, 4-aminomethyl- 2', 7'-difluorofluorescein diacetate and diamino-rhodamine-4M, respectively. Upon seedling exposure to the synthetic auxin naphthaleneacetic acid, NO accumulation was differentially enhanced in argah1-1 and argah2-1 compared with the wild type. In all genotypes, much 3-amino, 4-aminomethyl- 2', 7'-difluorofluorescein diacetate fluorescence originated from mitochondria. The arginases are both localized to the mitochondrial matrix and closely related. However, their expression levels and patterns differ: ARGAH1 encoded the minor activity, and ARGAH1-driven beta-glucuronidase (GUS) was expressed throughout the seedling; the ARGAH2::GUS expression pattern was more localized. Naphthaleneacetic acid increased seedling lateral root numbers ( total lateral roots per primary root) in the mutants to twice the number in the wild type, consistent with increased internal NO leading to enhanced auxin signaling in roots. In agreement, argah1-1 and argah2-1 showed increased expression of the auxin-responsive reporter DR5:::GUS in root tips, emerging lateral roots, and hypocotyls. We propose that Arg, or an Arg derivative, is a potential NO source and that reduced arginase activity in the mutants results in greater conversion of Arg to NO, thereby potentiating auxin action in roots. This model is supported by supplemental Arg induction of adventitious roots and increased NO accumulation in argah1-1 and argah2-1 versus the wild type.