Molecular characterization of His-Asp phosphorelay signaling factors in maize leaves: Implications of the signal divergence by cytokinin-inducible response regulators in the cytosol and the nuclei

Molecular characterization of His-Asp phosphorelay signaling factors in maize leaves:... Genes for histidyl-aspartyl (His-Asp) phosphorelay components (His-containing phosphotransfer proteins, HP, and response regulators, RR) were isolated from Zea mays L. to characterize their function in cytokinin signaling. Six type-A RRs (ZmRR1, ZmRR2, ZmRR4–ZmRR7), 3 type-B RRs (ZmRR8–ZmRR10), and 3 HPs (ZmHP1–ZmHP3) were found in leaves. All type-A RR genes expressed in leaves were up-regulated by exogenous cytokinin. Transient expression of fusion products of the signaling modules with green fluorescent protein in epidermal leaf cells suggested cytosolic and nuclear localizations of ZmHPs, whereas type-B ZmRR8 was restricted to the nucleus. Type-A RRs were localized partly to the cytosol (ZmRR1, ZmRR2, and ZmRR3) and partly to the nucleus (ZmRR4, ZmRR5, and ZmRR6). In the yeast two-hybrid assay, ZmHP1 and ZmHP3 interacted with both cytosolic ZmRR1 and nuclear type-B ZmRRs. In vitro experiments demonstrated that ZmHPs function as a phospho-donor for ZmRRs; turnover rates of the phosphorylated state were tenfold lower in ZmRR8 and ZmRR9 than in ZmRR1 and ZmRR4. These results suggest that the His-Asp phosphorelay signaling pathway might diverge into a cytosolic and a nuclear branch in leaves of maize, and that the biochemical nature of ZmRRs is different in terms of stability of the phosphorylated status. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Molecular Biology Springer Journals

Molecular characterization of His-Asp phosphorelay signaling factors in maize leaves: Implications of the signal divergence by cytokinin-inducible response regulators in the cytosol and the nuclei

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Publisher
Kluwer Academic Publishers
Copyright
Copyright © 2003 by Kluwer Academic Publishers
Subject
Life Sciences; Biochemistry, general; Plant Sciences; Plant Pathology
ISSN
0167-4412
eISSN
1573-5028
D.O.I.
10.1023/A:1023971315108
Publisher site
See Article on Publisher Site

Abstract

Genes for histidyl-aspartyl (His-Asp) phosphorelay components (His-containing phosphotransfer proteins, HP, and response regulators, RR) were isolated from Zea mays L. to characterize their function in cytokinin signaling. Six type-A RRs (ZmRR1, ZmRR2, ZmRR4–ZmRR7), 3 type-B RRs (ZmRR8–ZmRR10), and 3 HPs (ZmHP1–ZmHP3) were found in leaves. All type-A RR genes expressed in leaves were up-regulated by exogenous cytokinin. Transient expression of fusion products of the signaling modules with green fluorescent protein in epidermal leaf cells suggested cytosolic and nuclear localizations of ZmHPs, whereas type-B ZmRR8 was restricted to the nucleus. Type-A RRs were localized partly to the cytosol (ZmRR1, ZmRR2, and ZmRR3) and partly to the nucleus (ZmRR4, ZmRR5, and ZmRR6). In the yeast two-hybrid assay, ZmHP1 and ZmHP3 interacted with both cytosolic ZmRR1 and nuclear type-B ZmRRs. In vitro experiments demonstrated that ZmHPs function as a phospho-donor for ZmRRs; turnover rates of the phosphorylated state were tenfold lower in ZmRR8 and ZmRR9 than in ZmRR1 and ZmRR4. These results suggest that the His-Asp phosphorelay signaling pathway might diverge into a cytosolic and a nuclear branch in leaves of maize, and that the biochemical nature of ZmRRs is different in terms of stability of the phosphorylated status.

Journal

Plant Molecular BiologySpringer Journals

Published: Oct 7, 2004

References

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