Takei Kentaro, Ueda Nanae, Aoki Koh, Kuromori Takashi, Hirayama Takashi, Shinozaki Kazuo, Yamaya Tomoyuki, Sakakibara Hitoshi
Plant Science Center, RIKEN (Institute of Physical and Chemical Research), Suehiro 1-7-22, Tsurumi, Yokohama, 230-0045 Japan.
Plant Cell Physiol. 2004 Aug;45(8):1053-62. doi: 10.1093/pcp/pch119.
We analyzed the spatial expression pattern of Arabidopsis thaliana adenosine phosphates-isopentenyltransferase genes (AtIPT1, AtIPT3 to AtIPT8) and the effect of inorganic nitrogen sources on their regulation. In mature plants, the AtIPTs were differentially expressed in various tissues including the roots, leaves, stems, flowers and siliques. In transgenic seedlings expressing a gene for green fluorescent protein (GFP) driven by the AtIPT promoters, AtIPT1::GFP was predominantly expressed in the vascular stele of the roots, AtIPT3::GFP was in the phloem companion cells, AtIPT5::GFP was in the lateral root primordium and pericycle, and AtIPT7::GFP was in both the vascular stele and the phloem companion cells of the roots. In a long-term treatment, the accumulation level of AtIPT5 transcript was correlated with the concentrations of NO(3)(-) and NH(4)(+) in the growth medium. However, under nitrogen-limited conditions, AtIPT3 expression was rapidly induced by NO(3)(-) in the seedlings accompanying the accumulation of cytokinins, whereas AtIPT5 expression was little affected. The NO(3)(-)-dependent accumulation of both the AtIPT3 transcript and the cytokinins was markedly reduced in a Ds transposon-insertion mutant of AtIPT3. These results suggest that nitrogen availability differentially regulates expression of AtIPT3 and AtIPT5, and that AtIPT3 is a key determinant of cytokinin biosynthesis in response to rapid changes in the availability of NO(3)(-).
我们分析了拟南芥腺苷磷酸异戊烯基转移酶基因（AtIPT1、AtIPT3至AtIPT8）的空间表达模式以及无机氮源对其调控的影响。在成熟植株中，AtIPTs在包括根、叶、茎、花和角果在内的各种组织中差异表达。在由AtIPT启动子驱动绿色荧光蛋白（GFP）基因表达的转基因幼苗中，AtIPT1::GFP主要在根的维管束中表达，AtIPT3::GFP在韧皮部伴胞中表达，AtIPT5::GFP在侧根原基和中柱鞘中表达，AtIPT7::GFP在根的维管束和韧皮部伴胞中均有表达。在长期处理中，AtIPT5转录本的积累水平与生长培养基中NO(3)(-)和NH(4)(+)的浓度相关。然而，在氮限制条件下，幼苗中的AtIPT3表达在伴随着细胞分裂素积累的情况下被NO(3)(-)迅速诱导，而AtIPT5表达几乎不受影响。在AtIPT3的Ds转座子插入突变体中，AtIPT3转录本和细胞分裂素的NO(3)(-)依赖性积累均显著降低。这些结果表明，氮的有效性差异调节AtIPT3和AtIPT5的表达，并且AtIPT3是响应NO(3)(-)有效性快速变化的细胞分裂素生物合成的关键决定因素。
