His-Asp phosphotransfer possibly involved in the nitrogen signal transduction mediated by cytokinin in maize: molecular cloning of cDNAs for two-component regulatory factors and demonstration of phosphotransfer activity in vitro.
Implication of His-to-Asp and/or Asp-to-His (His-Asp) phosphorelay has been recently reported in signal transduction pathways initiated by ethylene and cytokinin. These signaling systems are generally composed of sensor His-protein kinases, His-containing phosphotransfer (HPt) domains, and response regulator domains. In this study, we isolated maize cDNAs, designated as ZmRR2 and ZmHP2, which encode a response regulator domain and HPt domain, respectively, and we identified their His-to-Asp phosphotransfer activity in vitro. The putative translated product of ZmRR2 was highly similar to that of ZmRR1 (78% identity), a maize response regulator homologue. The putative translated product of ZmHP2 showed similarity to that of HPt domains from Arabidopsis thaliana (AHP1-AHP3: 44 to 47% identity) and Saccharomyces cerevisiae (Ypdlp: 24% identity). In vitro experiments demonstrated that the putative signaling factors can transfer the phosphoryl group from His-80 of ZmHP2 to Asp-90 of ZmRRs. Treating detached leaves with t-zeatin or supplying inorganic nitrogen to the whole plant induced the accumulation of ZmRR1 and ZmRR2 transcripts. On the other hand, the steady-state transcript level of ZmHP2 was not affected by cytokinin or inorganic nitrogen sources. These results indicate that His-Asp phosphotransfer may be involved in the transduction of nitrogen signals mediated by cytokinin, and that multiple response regulators participate in the signaling pathways.
Sakakibara
H
H
Department of Biological Mechanisms and Functions, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Japan.
Hayakawa
A
A
Deji
A
A
Gawronski
S W
SW
Sugiyama
T
T
D000595:Amino Acid Sequence; D001224:Aspartic Acid / Q000378:metabolism*; D001665:Binding Sites; D015152:Blotting, Northern; D003001:Cloning, Molecular; D003583:Cytokinins / Q000494:pharmacology*; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006639:Histidine / Q000378:metabolism*; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000187:drug effects*; D014018:Tissue Distribution; D003313:Zea mays / Q000737:chemistry / Q000235:genetics; D015026:Zeatin / Q000494:pharmacology
D003583:Cytokinins; D018076:DNA, Complementary; D010940:Plant Proteins; D018749:RNA, Plant; C402568:ZmHP2 protein, Zea mays; D001224:Aspartic Acid; D006639:Histidine; D015026:Zeatin; D009584:Nitrogen