Accumulation of maize response regulator proteins in mesophyll cells after cytokinin treatment.
The maize response regulator genes ZmRR1 and ZmRR2 respond to cytokinin, and the translated products seem to be involved in nitrogen signal transduction mediated by cytokinin through the His-Asp phosphorelay. To elucidate the physiological function of the proteins, we examined the temporal and spatial distribution in maize leaves by immunochemical analysis and use of transgenic plants. ZmRR1 and ZmRR2 polypeptides could be distinctively detected by western blotting. The polypeptides accumulated in leaves within 5 h of the supply of nitrate to nitrogen-depleted maize, and the accumulation was transient. The extent of induction was larger in the leaf tip, which is rich in photosynthetically matured cells, than elsewhere. In leaves, the polypeptides accumulated mostly in mesophyll cells. Histochemical analyses of transgenic maize harboring a ZmRR1 promoter-beta-glucuronidase fusion gene also showed most of the expression to be in these cells. These results suggest that ZmRR1 and ZmRR2 are induced in mesophyll cells and function in nitrogen signal transduction mediated by cytokinin.
Deji
Atsushi
A
Department of Biological Mechanisms and Functions, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Japan.
Sakakibara
Hitoshi
H
Okumura
Shinya
S
Matsuda
Tsukasa
T
Ishida
Yuji
Y
Yamada
Shigehiro
S
Komari
Toshihiko
T
Kubo
Tomoaki
T
Yamaya
Tomoyuki
T
Sugiyama
Tatsuo
T
D003583:Cytokinins / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D009566:Nitrates / Q000494:pharmacology; D018515:Plant Leaves / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000032:analysis / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D030821:Plants, Genetically Modified; D015398:Signal Transduction / Q000187:drug effects; D003313:Zea mays / Q000166:cytology* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D003583:Cytokinins; D009566:Nitrates; D010940:Plant Proteins