Poster: Intracellular Signaling
Abs #
829: A novel Maize kinase (ZmS6K), turned to be a target of the signaling pathway that regulates Maize seedling growth.
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Presenter: |
Reyes de la Cruz, Homero , homeroreyes@yahoo.com |
Authors | Reyes de la Cruz, Homero (A) Dinkova, Tzvetanka D (A) Aguilar, Raul C (A) Sánchez de Jiménez, Estela (A) | | Affiliations: |
(A): Facultad de Química, UNAM
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Cell growth and proliferation in eukaryotes, is regulated by a signal transduction pathway that involves ribosomal protein S6 (S6rp) phosphorylation, and increasing translation of transcripts that encode ribosomal proteins1. The protein kinase that performs S6rp phosphorylation is called p70S6K in mammals although a plant homolog of this enzyme has not been characterized. In this work, we isolated a protein kinase that phosphorylates S6rp from Zea mays embryonic axes (ZmS6K). This enzyme was specifically recognized by anti-human p70S6K antibody. It showed substrate specificity for S6rp on 40S ribosomal subunit or RSK peptide. ZmS6K enzyme activation is achieved by phosphorylation on the equivalent mammalian target 389 threonine residue as suggested by immuno recognition of phospho-389-Threo specific antibodies. Expression of this protein in maize axes showed a steady level through germination; however, it was inactive in quiescent axes and fully activated at the end of germination. Addition of insulin/IGF, an effector of this signaling pathway, to maize embryonic axes resulted on ZmS6K activation and recruitment of TOP-like mRNAs into polysomes. Rapamycin, an inhibitor of the insulin/IGF-induced signal transduction pathway, proved to block ZmS6K and S6rp phosphorylation. These data strongly suggest that ZmS6K is homolog to the animal S6K (p70S6K) playing a similar role in the signal transduction pathway that regulates plant cell growth.
This research was supported by DGAPA-UNAM Grant No. IN-202900.
1Fumagalli S, Thomas G (2000) In: Sonenberg N, Hershey JWB, Mathews M (eds). Translational Control of Gene Expression. Cold Spring Harbor, New York: Cold Spring Harbor Laboratory Press, pp 695-717
